tp broadcast engineering - americanradiohistory.com · 2019-07-17 · here is a testimonial by jon...

CA1k. I. OWARD W. SAMS PU 3LICATION

OCTOBER 1967/75 cents

TP

Broadcast Engineeringthe technical journalo/ the broadcast -

cc mmunications industry

1

In three easy steps, you can build your way economically tothe same high quality deluxe color sync generator used by themajor TV networks. Start out with Riker's basic EIA syncgenerator-lour modules, rack frame and power supply-$2900. When your budget can afford the expansion, add twomore modules for deluxe sync lock and you get the advantageof three selectable speeds for locking to an externalcomposite video or sync signal. Cost: $790.

Now you're all set to step up to color. Add three moremodules-$-985-and you have eased into Riker's widely used,field -proven Model 520-4CL Color Sync Generator withDeluxe Sync Lock. You now own the best sync generatingsystem in the broadcast industry.

The Riker module at a time approach is the sensible way tobuild quality equipment into your facilities. Over the long termit's also the most inexpensive way. If you're interested indetails on sync generators, write or call Riker-the onecompany in the TV broadcast industry offering a complete lineof all solid-s:ate instrumentation for video analysis, simulationand control.

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Circle Item 1 on Tech Data Card

When it comes to cutting

TV switching costs

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COHU's got what it takes!

And that's everything you need-in stock-ready for immediate delivery from a singlesource.Our modular, off -the -shelf approach to building solid-state switchers is thoroughlyproven in use. Cohu switchers now operating include one of the largest ever built-over14 tons of solid-state gear accommodating 80 inputs and 160 outputs! Just shipped:two identical vertical interval switching systems for Chicago's newest UHF station.

We stock: monochrome/color switching matrix, switcher control and remote control units.Stocked accessories include sync generators, genlock, color standard, colorlock, automaticsync change -over switches, pulse and video distribution amplifiers, dot bar generators,monitors and portable vidicon cameras. Control panels are custom-built to your specifi-cations. Get full details direct or from your nearest Cohu engineering representative.

Box 623,San Diego, Calif. 92112Phone: 714-277-6700

October, 1967

ELECTRONICS, INCSAN DIEGO' CALIFORNIA

Circle Item 2 on Tech Data Card 3

publisherHoward W. Sams

general manager/sales directorDonald W. Bradley

editorWilliam E. Burke

managing editorJames M. Moore

associate editorHarold E. Hale

regional editorsGeorge M. Frese, NorthwestHoward T. Head, Wash., D.C.

Robert A. Jones, MidwestAllen B. Smith, North Central

research librarianBonny Howland

productionE. M. Rainey, Manager

Paul A. Cornelius, Jr., Photography

circulationPat Osborne, Manager

advertising sales offices

central and midwesternRoy Henry

Howard W. Sams & Co., Inc.4300 West 62nd St.

Indianapolis, Ind. 46206291-3100

easternAlfred A. Menegus

Howard W. Sams & Co., Inc.3 West 57th St.

New York 19, New YorkMU 8-6350

southwesternMartin Taylor

P.O. Box 22025Houston, Tex. 77027

713-621-0000

westernLOS ANGELES OFFICE

G. R. HoltzThe Maurice A. Kimball Co., Inc.

2008 West Carson St., Suites 203-204Torrance, California 90501

(213) 320-2204SAN FRANCISCO OFFICE

The Maurice A. Kimball Co., Inc.580 Market St., Room 400

San Francisco, California 94104(415) EX 2-3365

foreignLONDON W.C. 2, ENGLAND

John Ashcraft, Leicester SquareWHitehall 0525

AMSTERDAMJohn Ashcraft, Herengracht 365

Telefoon 24 09 08PARIS 5, FRANCE

John Ashcraft, 9 Rue LagrangeODeon 20-87

TOKYO, JAPANInternational Media Representatives,

Ltd., 1, Kotohiracho, Shiba,Minato-Ku, Tokyo

(502) 0656Copyright m 1967

by Howard W. Sams & Co., Inc.BROADCAST ENGINEERING is publishedmonthly by Howard W. Sams & Co., Inc., 4300West 62nd Street, Indianapolis. Indiana 46206.SUBSCRIPTION PRICES: U.S.A. $6.00, oneyear; $10.00, two years; $13.00, three years.Outside the U.S.A., add $1.00 per year forpostage. Single copies are 75 cents, backissues are $1.00.

the technical journal of the broadcast -communications industry

*Broadcast EngineeringVolume 9, No. 10

CONTENTS

Features

Color -TV Basics-ColorimetryA series presenting the fundamental concepts involved

in color transmission begins in this issue.

Radio Broadcasting on Medium FrequenciesThis examination of medium -frequency

broadcasting places emphasis on thepropagation mechanism: involved.

October, 1967

10

Alfred F. Barghausen, 20James W. Finney, andRonald M. Fisher

A System for Separate Repeater Origination W. H. Lindenbach 42A Canadian broadcasting organization uses

tape -cartridge equipment to originateseparate announcements over its

main and repeater stations.

Departments

Engineers' Exchange 6

Washington Bulletin 53

News of the Industry 58

New Products 67

Engineers' Tech Data 73

Advertisers' Index 76

Classified Ads 77

Soccer is the newest dimension in colorsportscasting. This month's cover showsa pickup (by CBC) of a soccer match forCTV, Canada's private color network. An

RCA color camera is covering a gamebetween England and Mexico in the

new "Autostade" at Montreal, directlyoutside the Expo '67 grounds.

(Photo courtesy of RCA)

Broadcast Engineering

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October, 1967

Circle Item 3 on Tech Data Card5

ADDCONTROLLED

DIMENSION

with the new

FAIRCHILDREVERBERTRONS!

The use of controlled rever-beration has gained wide ac-ceptance in the professionalrecording field because theuse of reverberation in severalmicrophone channels pro-duces records that have wideaudience appeal. Simplystated: reverberated soundproduces hit records. Sec-ondly, reverberated sound isapparently louder than thesame non -reverberated signal.

The use of reverb in broad-casting and sound re -enforce-ment is becoming equallymore popular for the samereasons: A more pleasingcommercial sound and pro-duction of a signal that is ap-parently louder for the samesignal level.

TWO COMPACTREVERB SYSTEMS...

Now FAIRCHILD has created twoelectro-mechanical reverberationsystems that produce a sound,termed by recording studio mixers-the experts who know what theyhear, as "extremely natural soundpossessing the quality of goodacoustical reverb chambers." Thetwo models differ more in theirflexibility and cost rather than inreverberation effect.

MODEL 658AThe 6588 is a complete solid

state reverberation system withelectronically controlled reverb

time adjustments up to5 seconds; mixing control tor

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reverb equalization at 2. 3 and5 KHZ. Size: 241/2 x 19"

MODEL 658BCompact, reverberation systemfor the 'big' sound in a smallspace. Contains reverb equalizationin mid and low frequency range;level control; solid state design.Size, Only 51/a x 3 x 10" deep.

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The "sound" of the Model 658A and 658BREVERBERTRONS will satisfy the most de-manding audio engineer. Their pricing andsize makes them even more appealing.

Write to FAIRCHILD-the pacemaker in profes-sional audio products - for complete details.

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Automatic Color Switcher

Some time ago, we felt the needfor a video-AGC unit in the lineto the transmitter for the purpose ofmaintaining a relatively constantlevel. At that time, no AGC unitswere available that would handle

color satisfactorily. Because of thisfact and the number of color broad-casts planned, a great deal of switch-ing of the AGC unit in and out ofthe circuit was indicated.

The use of a toggle switch forthis purpose was considered, but,

Please turn to page 40

CCABROADCAST

TRANSMITTERSTUBE LIFE IN CCA TRANSMITTERS ARE

EXCEPTIONAL - WHY PAY MORE AND GET LESS?HERE IS A TESTIMONIAL BY JON D. KIKERMr. Bernard Wise, PresidentCCA Electronics Corporation716 Jersey Avenue, Gloucester City, N. J. 08030Dear Mr. Wise:

We've had the CCA 10KW FM and the 5 KW AM trans-mitters on the air for a total of more than 20,000 oper-ating hours. Performance of both these equipmentsindicates that their purchase was a good choice. For ex-ample, the original AM final tube was replaced at 8,700operating hours -16 months after the transmitter went onthe air. Useful life of the AM modulator tubes was slightlybetter at 9,158 hours. No major tubes in the FM -10.000Dhave required replacement in its initial year of operationjust concluded. -

With our "good music" format on both AM and FM,WCOA places a great deal of emphasis upon a quality airsound, and both transmitters have met this requirementadmirably. Reliability speaks for itself when our recordsindicate less than three hours of lost air time in 37 cumu-lative months of operating both of them.

Your factory service has been second to none in theindustry. It's been a pleasure to deal with a firm whichbelieves in a 100 per cent backing of its claims to per-formance.

CCA

Yours very truly,

7'Jon D. KikerChief Engineer

Chief Engr., Station WCOAPensacola, Florida

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6 Circle Item 4 on Tech Data CardBROADCAST ENGINEERING

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Circle Item 6 on Tech Data CardOctober, 1967 7

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8Circle Item 7 on Tech Data Card

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October, 1967 9

COLOR -TV BASICS

COLORIMETRY

As an increasing number of television stations beginor increase color origination, more and more broadcasttechnicians will need to understand the color system.Also, many technicians already engaged in color workhave not had an opportunity for organized study of thesubject.

As a service to its readers, BROADCAST ENGI-NEERING this month begins publication of a seriesof articles on the fundamentals of the NTSC systemof color television. The series begins with an examina-tion of the characteristics of light and human visionthat combine to produce the sensation of color. Sub-sequent articles will show how the requirements im-posed by these physical phenomena are resolved withthe requirements of the television transmission system.--The Editor

Since the color television system had to be designedto reproduce images of things as they are seen in na-ture, the characteristics of light, vision, and color hadto be taken into consideration. Therefore, developmentof the system was greatly aided by applying the prin-ciples of colorimetry. the science and practice of deter-mining and specifying colors. It is not necessary to bean expert colorimetrist in order to understand themake-up of the color picture signal; however, a betterunderstanding of the color television system will beattained if some of the most important fundamentals ofcolorimetry are known. The principles of color as ap-plied to television are slightly different than those whichapply to other types of color reproduction.

Fig. 1. Cross section shows structure of the human eye.

Part 1 of a series describing thebasic principles of the NTSCcolor system.

The properties of light and vision should be under-stood before studying the principles of color. Light isthe basis of color, and the eye must be able to conveypicture sensation to the brain.

Vision

Human vision is a process which occurs partly inthe eye and partly in the brain. The light output froman object stimulates the eye, and this stimulation is

transferred to the brain where it is registered as a con-scious sensation.

The structure of the eye is similar in many respectsto that of a mechanical instrument. The eye consistsessentially of a lens system, a diaphragm (the iris)with a variable aperture (the pupil), and a screen (theretina). (See Fig. 1.) Light enters the eye through atransparent layer called the cornea and passes throughthe pupil to the lens, which is directly behind the iris.The amount of light which strikes the lens is controlledby the contraction and expansion of the iris; during alow light level the iris expands (pupil is larger), andduring a high level it contracts (pupil is smaller). Thelight is focused by the lens to form an image on theback wall, or retina, of the eye. The light falling onthe retina stimulates nerve terminals called rods andcones. These terminals are connected to the brain by agroup of nerve fibers called the optic nerve, which fur-nishes the path by which the vision impulses are trans-ferred from the eye to the brain.

The field of vision covers an angle of about 200degress horizontally and 120 degrees vertically. In thecentral region of the field of vision, the eye is responsiveto color and detail, whereas in the outer region it ischiefly sensitive to motion.

The limits of vision are determined mainly by fourfactors: intensity threshold, contrast, visual angle, andtime threshold. Intensity threshold is the lowest bright-ness level that can stimulate the eye; it is very muchdependent upon the recent exposure of the eye to light.When a person enters a darkened room, the eye is slowto reach its maximum sensitivity; the required time,which is usually about an hour, differs among individ-uals. When a person returns to a lighted area, the timeneeded for the eye to reach its maximum sensitivity isrelatively short, just a matter of minutes.

Contrast represents a difference in the degree of


brightness. The limit of vision with respect to contrastis the least brightness difference that can be perceived.The eye is sensitive to percentage changes rather thanto absolute changes in intensity.

As an object is made smaller or is placed at a greaterdistance from the eye, the angle formed by the lightrays from the extremities of the object to the eye be-comes smaller. This angle is referred to as the visualangle. In order for the eye to respond, the visual anglemust be such that the image covers a definite minimumarea on the retina. This principle is used in eye testsin which the viewer is asked to read the smallest letterspossible; those letters which he cannot read produceon the retina an image that is too small to be useful tothe eye. The minimum visual angle is dependent uponthe contrast and brightness of the image; for example,an object having sharp contrast could be distinguishedat a narrow visual angle while an object having thesame size but a lower contrast might not be visible.The same principle applies to a change in brightness;a very small object can be seen more easily at a highbrightness level than at a low brightness level.

There is a minimum time during which a stimulusmust act in order to be effective. This is called thetime threshold. If the exposure interval is too short, therods and cones of the eye do not have time to respondto an image on the retina. The time threshold is alsodependent upon the size, brightness, and color of theobject.

Other factors which pertain to the characteristics ofvision are:

1. Sensitivity to detail is increased by high contrast,sharp edges, and motion.

2. Straight lines are more readily resolved thancurved lines. Horizontal or vertical lines are more easilyresolved than diagonal lines.

3. Altering the background of an object changesthe appearance of the object; a gray object appears

lighter when it is placed on a black background, butit appears darker when placed on a white background.

Light Sources

The foregoing has shown how the eye is capable ofseeing. However, for this process to occur there firstmust be a source of light to illuminate the object seen.Two types of light will be considered. Light such asthat coming from the sun or emitted from some artificialsource such as an electric lamp is referred to as directlight. Indirect, or reflected, light is given off by anobject when direct light strikes it. The difference be-tween these two types of light is that indirect light isdependent upon direct light. When an object does notreceive direct light, no light is given off unless the objectpossesses self-luminating properties.

Direct light falling upon an object is either absorbedor reflected. The larger the amount of light that is re-flected by an object, the brighter the object will appearto the eye. In addition, the more intense the direct lightsource, the brighter the object will become.

Light is a form of radiant energy similar to X-raysand radio waves, and it is considered to travel by wavemotion. As shown in Fig. 2, light which is useful tothe eye occupies only a small portion of the radiant-energy spectrum. Along the top of the spectrum illus-trated in Fig. 2 is the frequency scale, and along thebottom is the Angstrom -unit scale (1 Angstrom unit =10" cm). Wavelengths in the region of light may bedesignated in microns (1 micron = 10-4 cm). Theseunits are also shown along the bottom of the spectrumin the illustration. Light is made up of that portion ofthe spectrum between 400 and 700 millimicrons.

When all wavelengths of the light spectrum from 400to 700 millimicrons are presented to the eye in nearlyequal proportions, white light is seen. Thus white lightis made up of various wavelengths, which are repre-

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1.-COSMIC-RAY S

I VISIBLE ..- GAMMA -.4

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I I I I I I I

10 16 1015

ANGSTROM UNITS -

1013 1011 109 107 106

MICRONS § 8

104 103

- c a-ci

102 100

E

'0-2

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to -4

Fig. 2. This chart represents the classification of different wavelength regions of the radiant -energy spectrum.

October, 1967 11

PRISM

SOURCE Li AllikmitWHITELSCREEN

R

Fig. 3. Prism produces color from beams of white light.

sentative of different colors. This composition can bedemonstrated by the use of a prism, as shown in Fig.3. The light spectrum is broken up into its constituentwavelengths, with each representing a different color.The ability to disperse the light by a prism stems fromthe fact that light of shorter wavelengths travels slowerthrough glass than does light of longer wavelengths.Fig. 4 shows the relationship of the wavelengths andthe colors of the light spectrum. Six distinct colors arevisible when white light is passed through a prism.Since the colors of the spectrum pass gradually fromone to the other, the theoretical number of colors be-comes infinite. It has been determined that about 125colors can be identified over the visible gamut. Fig. 5shows the light spectrum in full color.

How Color Appears to the EyeIt has been shown that light possesses various wave-

lengths covering the visible spectrum, and the spectrumis divided into various colors. Even though the colorswhich make up a white light may be of equal inten-sities, the human eye does not perceive each color withequal efficiency. This fact is due in some way to thephysical construction of the eye. It is believed that thecones of the retina respond to color stimuli and thateach cone is terminated by three receptors. Each recep-

1.0

0.8

00

3

13 04

Q2

000450 500 550 600

WAVELENGTH IN MILLMCRONS650 700

ULTRAVIOLET VIOLET BWE GREEN

a0- 0

5RED INFRARED

400 455 690 550 580 620

WAVELENGTH IN MILLIMICRONS

Fig. 4. Wavelength vs color relationship for visible light.

tor is believed to respond to a different portion of thespectrum, with peaks occuring in the red, green, andblue regions, respectively. An average can be taken ofthe color response of a number of people, and a stan-dard response for an average person can be derived.This standard response is shown in Fig. 5 and is calledthe luminosity curve for the standard observer.

An inspection of this luminosity curve shows thatmaximum response occurs at a wavelength of approxi-mately 555 millimicrons and that less response is indi-cated on either side of that point. From this informa-tion, one may see that the average person's eye is mostsensitive to light of a yellowish -green color and is lesssensitive to blue and red lights.

There are three color attributes which are used todescribe any one color or to differentiate between col-ors. These are: (1) hue, (2) saturation, and (3)brightness. Hue is a quality which is used to identifyany color under consideration, such as red, blue, oryellow. Saturation is a measure of the absence of dilu-tion by white light and can be expressed with termssuch as rich, deep, vivid, or pure. Brightness definesthe amount of light energy contained in a given color.

An analogy between a color and a radiated radiowave can be used to explain the three attributes ofcolor. Hue, which defines the wavelength of the color,

Fig. 5. Luminosity response of the eye depends on color.

12

Fig. 6. Color perception depends on area of the object.


is analogous to frequency, which defines the wavelengthof the radio wave. Saturation, which defines the purityof the color, is analogous to signal-to-noise ratio, whichdefines the purity of the radio wave. Brightness, whichis governed by the amount of energy in the color, is

analogous to amplitude, which defines the amount ofenergy in the radio wave. Brightness is a characteristicof both white light and color, whereas hue and satura-tion are characteristics of color only.

Saturation and brightness often are visualized asidentical or interrelated qualities of color, but theyshould be considered as separate qualities. It is possibleto vary either one of them without changing the other.For example, an oscilloscope presents a green trace onthe face of the tube; this trace can be varied in bright-ness from visual extinction to a maximum brightnessby rotation of the intensity control. An observer canbecome confused by the fact that the green color ap-pears to be greener at low intensity levels than it is athigher intensities. This is often interpreted as an increasein saturation at the low intensity level. Actually, how-ever, neither the hue nor the saturation of the tracecolor can change since these qualities are determinedby the chemical properties of the phosphor. The bright-ness of the trace is the only variable when the intensitycontrol is rotated. The deceiving change in saturationis caused by a change in the color response of the eyeat low intensity levels.

In the foregoing example, the brightness level wasvaried without changing the saturation. Conversely,the saturation of a given color can be changed withoutvarying the brightness, providing certain requirementsare met during the process.

In nature, however, a change in saturation is usuallyaccompanied by a change in brightness. This is exem-plified by the fact that a pastel color generally appearsbrighter than a saturated color of the same hue whenthey are directly lighted by the same source. By chang-ing, the lighting on the pastel color (such as by placingit in a shadow), one can decrease the brightness of thepastel color, and it is conceivable that both colors canbe made to have the same brightness. Thus, two colorsof the same hue but of different saturation can haveequal brightness levels.

Any given color within limitations can be reproducedor matched by mixing three primary colors, as will beexplained later. This applies to large areas of coloronly. Color vision for small objects or small areas ismuch simpler, because only two primary colors areneeded to produce any hue. This is because as thecolor area is reduced in size it becomes more difficultto differentiate between hues, and for small areas everyhue appears as gray. At this point a change in hue isnot apparent; only a change in brightness can be seen.

As an example, a large area of blue can be distin-guished readily from a large area of blue-green; how-ever, when these areas are reduced in size, it becomesmore difficult to distinguish between the two colors.Fig. 6 illustrates this characteristic when it is viewedat arm's length.

Experiments have been made using sheets of multi-colored paper cut in various sizes. A number of things

were discovered as these pieces were reduced in sizeand viewed at a distance.

1. Blues become indistinguishable from grays withequivalent brightness.

2. Yellows also become indistinguishable fromgrays. In the size range where this happens, brownsare confused with crimson and blues with greens; redsremain clearly distinct from blue -greens; colors withpronounced blue lose blueness; and colors lacking inblue gain blueness.

3. A further decrease in size results in reds mergingwith grays of equivalent brightness, and blue -greensbecome indistinguishable from grays.

When viewing extremely small objects, the ability ofthe human eye to identify color is lost, and only re-sponse to brightness remains. Fig. 7 shows clusters ofcolored dots of three different sizes. Note that a de-crease in dot size makes color identification more dif-ficult. (Hold the page at arm's length when viewingthis figure.)

Another aspect of color vision is closely related tothe persistence of vision exhibited by the human eye.If two objects of different hue are placed side by sideand are shuttled back and forth at a sufficiently rapidrate, the two hues will appear as a third hue. This istrue for both large and small objects.

Color Mixture

The production of color may be accomplished byeither of two processes. The subtractive process is em-ployed when paint pigments are involved, and theadditive process is employed in color television. Thesetwo methods of producing color are rather different; itmight be said that the additive process is just the reverseof the subtractive process.

Fig. 7. The perception of color in small areas is poor.

October, 1967 13

The subtractive process is dependent upon incidentlight. Light falling on a painted picture is reflected orabsorbed. If a certain section of the picture is treatedwith a red pigment, the light which is reflected is pre-dominantly in the red region of the spectrum, and thesection will appear red.

The additive process employs lights for the produc-tion of colors; the colors do not depend upon an in-cident light source. Self -luminous properties are charac-teristic of the additive colors, so since cathode-ray tubescontain self -luminance properties, it is only logical thatthe additive process would be employed in television.

The three primaries for the additive process of colormixing are red, green, and blue. Two requirements forthe primary colors are that each primary must be dif-ferent and that the combination of any two primariesmust not be capable of producing the third. Red, green,

Fig. 8. Red, green, and blue are the additive primaries.

Fig. 9. A color circle illustrating combinations of colors.

Red

Blue

Yellow

Cyan

and blue were chosen because they fulfilled these re-quirements and because it was determined that thegreatest number of colors could be matched by thecombination of these three colors.

Shown in Fig. 8 are the three additive primaries usedin color television. Fig. 8A shows the primaries asthree separate colored lights. Addition of the threecolored lights is shown in Fig. 8B. When all three pri-maries are combined in a definite proportion, white isproduced. Red and green combine to make yellow. Thecombination of red and blue produces magenta (bluish -red), while blue and green combine to make cyan(greenish -blue). Yellow, magenta, and cyan are thesecondary colors that are the complements of blue,green, and red, respectively. When a secondary color iscombined with its complementary primary, white isproduced. For example, combining yellow with blueproduces white. Cyan added to red results in white, andmagenta plus green gives white. Carrying this one stepfurther, the complementary colors when added togetherproduce white. It should be mentioned that specificproportions of these colors must be used in order toproduce white.

The foregoing points are shown diagrammatically inFig. 9. This diagram illustrates that, when colors aremixed in certain proportions, these expressions apply:

Red + Green = Yellow,

+ Blue = Magenta,

+ Green = Cyan,

+ Blue = White,

+ Red = White.

Magenta + Green = White.

Since yellow plus blue equals white and red plus greenequals yellow, then

Red + Green + Blue = White.Since the addition of the three primaries can producewhite, the addition of the correct proportions of thethree complementaries which are made up of the threeprimaries can also produce white. Therefore:

Cyan + Magenta + Yellow = White.It is not necessary to overlap the primary colors in

the additive process to produce a different color. Twosources of color may be placed in close proximity toeach other, and at a certain viewing distance the twocolors will blend together and produce the new color.The eye actually performs the additive process. This isreferred to as the juxtaposition of color sources. Forexample, if blue and green are positioned close to eachother but not overlapping, the two colors will be blendedby the eye and will be seen as cyan when viewed froma distance.

14 BROADCAST ENGINEERING

CHART I.

Color Matching Rules.

1.

Any color, with limitations, can bematched by a mixture of three coloredlights.

2.The individual colors which make up amixture cannot be resolved by the eye.

3.The total brightness of a mixture is

equal to the sum of the individualbrightnesses of all colors in the mixture.

4.If a color match is obtained at onebrightness level, the match will be main-tained over a wide range of brightnesslevels. If the brightness of the color tobe matched is doubled, a perfect colormatch will be maintained if the bright-ness of each color in the matching mix-ture is doubled.

5.A color equation can be used to expressthe formation of a color match. If a color(C) is formed by adding M units of color(M), N units of color (N), and P units ofcolor (P), the resulting mixture can bewritten:

(C) = M(M) N(N) P(P).

6.Color matches obey the law of addition.

If (M) = (N)and (P) = (Q)then (M) + (P) (N) (Q).

7.Color matches obey the law of subtrac-tion.

If (M) (P) (N) (Q)and (P) (Q)then (M) = (N).

8.Color matches obey the transitive law.

If (M) - (N)and (N) (P)

then (M) (P).

-.."411441100..CAN BE IIIIIMATCHED

411111BY

_/0111 .111111111

- - 1111

-'""1"1111114111%1111111°P"..4..

=, +

I:0-TOMATCH,USE -go

1:::) 111

1:0

AT HIGHER BRIGHTNESS LEVEL,MATCH CAN BE MAINTAINED BY

11:0-..

TOMATCH,USE -00

KOVcaKO 411111\i....c0

(1)

-- 1--- DM CM) + N CND + P CP) = (C)

I F CM) MATCHES (N)

AND (P) MATCHES (Ct)

THEN CM) + (P) -2: CN) + (Q)

IF CM) + (P) = CN) + (Q)

AND (P) MATCHES (C)

THEN CM) MATCHES (N)

IF THESE MATCH AND THESE MATCH

+ena + + +enll IIIIIIIIIMIITI 1111111,111111+ (M) (N) (P)

THEN THESE MATCH

Fig. 10. Chart shows eight rules for color matching together with a diagrammatic example to illustrate each rule.

October, 1967 15

480 520 560 600WAVE LENGTH IN MILLIMICRONS

Fig. 11. Color -mixture curves based on data from tests.

Each additive primary contributes a certain per-centage of the brightness in the white which resultsfrom mixture. With the total brightness of white con-sidered as unity, green contributes 59 per cent of thetotal, red 30 per cent, and blue 11 per cent. Therefore,combining green with red results in a yellow with abrightness value of 89 per cent. Cyan has a brightnessof 70 per cent, which results from 59 per cent of bright-ness from green and 11 per cent of brightness from blue.The third complementary color, magenta, has abrightness of 41 per cent, 30 per cent from red and 11per cent from blue. Yellow contains the highest percent of brightness of all of the primary colors and theircomplements, whereas blue contains the least amountof brightness. The relative brightness for each coloris shown in Fig. 8B.

There are eight basic rules of colorimetry whichapply to the process of color matching. These rulesare stated in Fig. 10, which also contains an illustra-tion applying to each rule. A knowledge of these rulesis quite helpful in understanding how matching of col-or can be accomplished using three primary colors.

Color Specifications

Standards are necessary in all phases of industry,and particularly in television where a broadcast con-forming to one set of transmission specifications could

not be received on equipment designed for reception ofa signal having different specifications. Similar difficul-ties would exist in the specification of colors if stand-ards were not adopted. Such terms as "purple," "pur-plish -red," or "bluish -purple" obviously are inadequatewhen an accurate color match is required.

Standards for the specification of color were adoptedby the Commission Internationale de l'Eclairage (CIE)at a meeting in 1931. (The English translation of thisFrench name is International Commission on Illumina-tion.) These standards provide that the red primaryshall correspond to a light having a wavelength of 700millimicrons, green to a wavelength of 546.1 milli -microns, and blue to a wavelength of 435.8 milli -microns.

In the development of a color matching and specifi-cation system, extensive color -matching tests on manyobservers were conducted using a colorimeter. This isa device which incorporates a photoelectric screen anda series of filters and optical lenses. The method usedin these color -matching tests was as follows: One halfof the colorimeter screen was illuminated with a spec-tral hue obtained by projecting the light from a standardsource of white light through a prism. The hue wasselected by moving a plate with a very narrow slit intoposition so that only the desired hue was allowed toilluminate the colorimeter screen. The other half ofthe colorimeter screen was then illuminated selectivelyby the observer with spectral hues of the three additiveprimaries-red, green, and blue. By the use of inde-pendent controls, the energies contributed by each ofthe primaries were varied by the observer until a colormatch was thought to be obtained. Each observer wassubjected to a series of tests which constituted attemptsto match several selected colors. In order to establishan average which could be considered as that of astandard observer, many persons were used with eachperforming similar tests. The results of these tests areknown as tristimulus values for color -mixture curvesand are illustrated in Fig. 11.

Tristimulus values are defined as the amounts of theprimaries (red, green, and blue) that must be combinedto achieve a color match with all the different colorsin the visible spectrum (400 millimicrons to 700 milli-microns). As an example of how this graph is used,consider a color which has a wavelength of 520 milli-microns. The amount of the three spectral primariesneeded to match this color can be read from the color-mixture curves. From the graph it can be seen thatapproximately .09 of red, .09 of blue, and .7 of greenare needed.

The data contained in the color -mixture curves arenot very practical for the specification of all colors.These curves contain information that is required todetermine the amounts of the spectral primaries neededto match any saturated spectral color. They do notprovide information necessary for the matching of de -saturated colors; therefore, the need for a more usefulmeans of specifying color is evident.

By the use of mathematical equations, the informa-tion contained in the color -mixture curves has been


Fig. 12. Three-dimensional color rep-resentation based on color -mixturecurves. Colors show capabilities of inksused in modern color printing method.

Fig. 13. Projection in the X -Y plane ofthe three-dimensional color diagram.

October, 1967 17

converted to a three-dimensional graphical representa-tion of color. The conversion equations used to derivethe three-dimensional coordinate values x, y, and z are:

Y -x + y- + -z

z - z+ y + z

where

= values on the red color -mixture curve,y = values on the green color -mixture curve,7 = values on the blue color -mixture curve.

Following are three example computations using theseequations.

For a green color of 560 millimicrons, the values of7, 7, and 7 are I = .6, 7 = 1. and 7 = 0. Substitutingthese values into equations 1, 2, and 3 gives:

x =.6 - .375.

.6 + 1 + 0

Y

z -

1

- o.

.6 + 1 + 0

.6 + 1 + 0

For a blue color of 480 millimicrons, the values are= .1, y = .15, 7 = .78. When these values are

substituted into equations 1, 2, and 3,

=. 1 - .097,

.1 + .15 + .78

.15Y - .146,

.1 + .15 + .78

z =.78 - .757.

.1 + .15 + .78

For a red light of 600 millimicrons, the values are= 1.06, y = .62, and 7 = 0. Then

1.06x - - .63,1.06 + .62 + 0

.621.06 + .62 + 0 - .37,

0z - - O.1.06 + .62 + 0

If the procedure is repeated at regular intervals from400 to 700 millimicrons, the results can be used to plotthe curve shown in Fig. 12. The ratios shown in equa-tions 1, 2, and 3 were set up so that the values for x,y, and z at any wavelength would equal unity whenadded together. similar curve can beshown on a two-dimensional plane; this curve consti-tutes a more useful diagram than that shown in Fig.12. Any two of the quantities x, y, and z are sufficientto specify a chromaticity. The third quantity can befound, since x + y + z = 1. By plotting only thevalues for x and y on the X -Y plane or by projectingthe curve of Fig. 12 to the X -Y plane, the result shownin Fig. 13 is obtained. The curve in this illustration iscalled the "CIE Chromaticity Diagram." (The projec-tion shown in Fig. 13 was accomplished by photo-graphing the structure shown in Fig. 12 from aboveand along the Z-axis. This eliminated the dimension onthe Z-axis and provided a proportionate diagram havingonly X and Y axes.) The two-dimensional CIE chro-maticity diagram shown in Fig. 13 is used extensivelyin the specification of color, since all colors containedwithin the locus of the CIE diagram can be specifiedin terms of X and Y.

In Fig. 13, the horseshoe curve, which is known asthe spectrum locus, is graduated with numerals rang-ing from 400 in the left-hand corner to 700 at theextreme right. These figures represent the wavelengthsof the various colors in millimicrons; the blues (in-cluding violet) extend from approximately 400 to 490millimicrons, the greens extend from approximately 490to 550 millimicrons, the yellows extend from approxi-mately 550 to 580 millimicrons, and the reds (includingorange) extend from approximately 580 to 700 milli-microns.

Any point which is not actually on the spectrumlocus but which lies within this diagram can be defined


as some mixture of spectrum colors. Since white is

such a mixture, it falls within this area.It might be well to point out that there is another

method of specifying colors near the white region. Thismethod uses degrees Kelvin to designate a particularcolor. (Degrees in Kelvin equal degrees in Centigradeplus 273.) As metal is heated to various temperatures,it changes in color from dull cherry red into a whiteas the temperature is increased. If the temperature isincreased still further, the metal takes on a decidedlybluish cast. These colors can be shown on the chro-maticity diagram by drawing an imaginary arc startingin the reddish region on the right side of the diagramand extending up through the orange into the whitearea and down toward the bluish region to the left. Suchfacts are of importance when considering the threestandard sources of light and how they were specifiedby the CIE. These sources are known as illuminant A,illuminant B, and illuminant C.

Illuminant A was selected as a match in color to aconventional tungsten lamp. To achieve this, a tungstenfilament was heated to approximately 2500 °K.

Illuminant B was selected to give an approximatematch to direct sunlight. It was achieved in the samemanner as illuminant A, except the tungsten filamentwas used with two prescribed liquid filters to give acolor which matches 4800 °K.

Illuminant C gives a radiation which most nearlymatches daylight. Tungsten filaments were used withthe filter solutions arranged so that they would producea color of approximately 6500 °K. Illuminant C is theonly one of concern here. Because it is considered tobe the most satisfactory from a viewing standpoint, itis the one which has been selected by the NTSC asthe reference white for color television work. It is

shown in the chromaticity diagram as point C.With reference to white, one other term which may

be encountered is "equal energy white." This is shownon the chromaticity diagram as point E and can bedescribed as white composed of equal amounts of en-ergy from the three primary colors, red, green, and blue.

Since saturation of color is defined as the degree offreedom from white, the spectrum colors which liedirectly on the horseshoe curve can be said to be 100per cent saturated because they contain zero amountof white. At point E, only white light is present, so itcan be said to be zero per cent saturated. Variousintermediate percentages of saturation fall along astraight line drawn between any point on the spectrumlocus and point E.

Referring again to the chromaticity diagram in Fig.13, notice that the bottom of the horseshoe curve hasbeen completed with a straight line drawn from pur-plish -blue to red. Although this line completes thecurve, it should not be considered in the same senseas the rest of the horseshoe. The reason for this is thatthe colors along this line cannot be assigned dominantwavelengths within the limits of the spectrum; there-fore, these colors are known as nonspectral colors.They can, however, be expressed as the complementsof some of the spectrum colors which fall directly onthe horseshoe curve. A line from 500 millimicrons hasbeen extended through white to the straight line, and

the point of intersection is labeled 500C; or, in otherwords, the nonspectral color at the point is the com-plementary color of the bluish -green of wavelength 500millimicrons. The same thing is true of the line thathas been extended from a wavelength of 560 milli -microns; 560C is the complementary color of a yel-lowish -green with wavelength 560 millimicrons.

When primary colors were selected for color -tele-vision work, it was found that those primaries must ofnecessity be limited by the color phosphors that wereavailable for the picture tube. Fig. 13 shows the lo-cations of the actual primaries (R, G, and B) that areused in color television. They define a triangle withinthe boundaries of the chromaticity diagram; the areawithin the triangle represents the range of colors thatare obtainable when these primaries are used. In theNTSC triangle, red has a wavelength of approximately610 millimicrons, green is approximately 540 milli -microns, and blue is approximately 470 millimicrons.At first glance, this triangle appears much smaller thanthe gamut of colors obtainable when ideal primariesare used. Closer inspection reveals, however, that theNTSC primaries fall very close to the saturated colorson the chromaticity curve. The red primary, for ex-ample, is actually on the curve.

Fig. 12 also shows the colors obtainable from modernprinting inks. It is apparent that the NTSC color tri-angle covers a considerably larger area than does thegamut of printing inks.

Summary

The characteristics of human vision are importantin that the eye is the instrument which judges the qual-ity of color reception. Human vision is a remarkablefunction, but it has certain deficiencies and irregularitieswhich limit its effectiveness. An understanding of theselimitations is extremely helpful to anyone engaged incolor television work. Examples of these limitationsare: the luminosity response of the eye to various col-ors, intensity alid time thresholds, contrast limitations,and the visual -angle requirements. It was also pointedout that certain illusions occur particularly with respectto brightness and saturation changes.

Treatment has been given to the two types of lightsources, direct and indirect. In addition, the constit-uent colors and wavelengths of the light spectrum havebeen investigated. The attributes of hue, saturation, andbrightness were described.

The development of the chromaticity diagram wascovered in some detail. There were two major reasonsfor this: (1) The diagram is based upon actual testsof human vision, and this fact lends authority to thedata which it presents; and (2) the NTSC triangle,which can be put to practical use, is based to a greatextent upon the chromaticity diagram.

Since in the color television system the desired col-ors are produced by a mixing action, a thorough cover-age of color -mixture rules has been presented. Theserules are basic, and a knowledge of them will provehelpful in analyzing and adjusting color equipment.

Next month, consideration will be given to the re-quirements of the composite color signal.

October, 1967 19

RADIO BROADCASTING ON MEDIUM FREQUENCIESby Alfred F. Barghausen*, James W. Finney*, and Ronald M. Fisher*

A detailed examination of the use of the me-dium -frequency band for broadcast purposes.

The Radio Spectrum

"Medium frequencies" lie within that portion of theradio spectrum between 300 kHz and 3000 kHz. Thisrange is also designated in the International RadioRegulations of the International TelecommunicationsUnion (ITU) as Band 6, since the frequency 10' Hz liesnear its middle. The wavelength range corresponding tothis frequency range is of the order of 100 to 1000meters, and these are called hectometric waves. Fre-quency limits are arbitrarily assigned for conveniencein telecommunication usage rather than on the basisof propagation characteristics and the mechanisms in-volved.

There are other frequency designations for the vari-ous bands. A uniform nomenclature of the frequencyand wavelength bands as adopted by the ITU is givenin Table 1.

Different propagation mechanisms, i.e., methodswhereby electromagnetic waves travel from the trans-mitter to the receiver, are involved in various parts ofthe spectrum. Each band or series of bands may involvemore than one propagation mechanism at a time. Boththe ground -wave and sky -wave propagation mech-anisms, for example, are important at medium fre-quencies. Good -quality reception is simultaneouslyavailable at moderate distances by the ground waveand at long distances by the sky wave; at intermediatedistances, phase -interference selective fading, causedby interference between the ground wave and a time-delayed sky wave, often seriously deteriorates the auralquality of the received broadcast signals. Due to

TABLE 1. Nomenclature of Frequency Bands

Band

Designation Band No. ' Frequency Range t Metric Subdivision

VLF 4 3-30 kHz Myriametric WavesLF 5 30-300 kHz Kilometric WavesMF 6 300-3000 kHz Hectometric WavesHF 7 3-30 MHz Decametric WavesVHF 8 30-300 MHz Metric WavesUHF 9 300-3000 MHz Decimetric WavesSHF 10 3-30 GHz Centrimetric WavesEHF 11 30-300 GHz Millimetric Waves

12 300-3000 GHz DecimillimetricWaves

*Note that band b extends from 0.3 X 10" to 3 X 10° hertz and bmay be either a positive or a negative integer or may be equal to zero.tin international and national usage, the hertz (symbol: Hz) has beenaccepted alternatively with cycles per second (c/s) as the name for theunit of frequency. However, there is a strong tendency at present to usethe hertz (31).

ionospheric characteristics, however, the sky waves arepresent only during the hours of darkness.

Frequency assignments are made by a governmentagency within each country. International coordinationof frequency assignments is carried out by the Inter-national Frequency Registration Board (IFRB) of theITU or by separate treaty between adjacent countries.In both cases, regulations are adopted which attemptto provide assignments which yield service areas ade-quate for the intended purpose. Whether or not thesignals within the intended service areas are free fromharmful interference depends, to a large extent, on thetechnical considerations used for making the frequencyassignments.

Radio Broadcasting

Radio broadcasting is radio transmissions intendedfor general reception within geographic areas as dis-tinguished from radio communications directed to spe-cific receiving stations.

The frequency range 535 kHz to 1605 kHz is usedexclusively on a worldwide basis for medium -waveradio broadcasting and is sometimes referred to as the"standard broadcast band." Each station is assigned achannel which is a band of frequencies occupied bythe carrier and sidebands of the broadcast signal, withthe carrier frequency at the center. Channels are desig-nated by the carrier frequency.

In North American countries and Australia, frequencyassignments are made to channels beginning at 540kHz and having a bandwidth of 10 kHz. In the Eu-ropean area, Africa, and certain parts of South Amer-ica, the channels begin at 539 kHz and have a band-width of 9 kHz.

The Service Area Concept

For purposes of frequency assignment and deter-mination of effective range, the service -area conceptis used for all three types of broadcasting-amplitudemodulation (AM), frequency modulation (FM), andtelevision (TV). Amplitude -modulated broadcasting isused exclusively in the standard broadcast band, and theeffective range has been classified by the Federal Com-munications Commission (FCC) into three types ofservice areas as follows:1. Primary Service Area. The area in which theground -wave field strength is above a specified value

*Institute for Telecommunication Sciences and Aeronomy (formerlyCentral Radio Propagation Laboratory of the National Bureau ofStandards). Environmental Science Services Administration, Boulder.Colorado.


and is not subject to objectionable interference orfading.2. Secondary Service Area. The area in which the sky -wave field strength is above a specified value for agiven percentage of the time and is not subject to ob-jectionable interference.3. Intermittent Service Area. The area in which theground -wave field strength is above the specified valuein 1, but the signal is subject to interference from thesky wave for a given percentage of the time.

While it is not specifically stated in the above defini-tions, broadcast service areas can be described ac-curately only by statistical methods, i.e., the fractionof the locations within a specified area at which a spe-cified grade (quality) of service is available for a givenfraction or more of the time. The fraction of the timehas traditionally been expressed as a percentage, butthis introduces an essentially redundant factor of 100which unnecessarily complicates the algebra of thestatistics (1, 2, 3). It is possible to determine statisti-cally the ratios of wanted signal power to interferingsignal power necessary to produce sound of a qualityacceptable to different observers in the presence ofvarious types of interference (atmospheric noise, man-made noise, other stations, etc.). This is usually donefor each type of interference and six different grades ofservice-Excellent, Fine, Passable, Marginal, Inferior,and Unstable-with a number of observers under con-trolled conditions. The ratio accepted by half of theobservers for a given grade of service is chosen asthe acceptance ratio for that grade of service and typeof interference. Since the sky wave and even the groundwave may vary with time, it is also necessary to specifythe required fraction of time that the acceptance ratiomust be exceeded to define completely a given grade ofservice at a particular location. The location probabilityis then defined as the probability of receiving this qual-ity of service for a given part of the time or more (3).

In AM sound broadcasting, service areas are shownby isoservice contours (4). These contours describeareas of equal service availability and not limits ofservice. In any given area within the isoservice contour,only a fraction of the population (the location pro-bability times the population density) is expected tohave service of a given quality available for a givenfraction of the time or greater. This fraction represent-ing the location probability varies from area to areaand tends to decrease with increasing distance from thetransmitter. Quality of service does not change ab-ruptly, as might be inferred from a drawing of iso-service contours of various orders of magnitude, butshades gradually from service of high quality to serviceof low quality.

Ground -Wave Propagation

The ground wave can be defined as that part of thetotal received field which has not been reflected fromthe ionosphere or troposphere. For clarification, it isconvenient to divide the ground wave into two com-ponents, a surface wave and a space wave (5, 6, 7, 8).Wait (9) has proposed that this surface wave be des-

ignated the Norton surface wave in order to distinguishit from other surface waves. The Norton surface wave,as the name implies, is the electromagnetic energywhich is propagated over and diffracted around theearth's surface. The space wave is the sum of the directand ground reflected waves and normally is only im-portant at higher frequencies for line -of -sight transmis-sions, but may become dominant at lower frequenciesif either or both the transmitting and receiving antennasare sufficiently high above the earth.

At medium frequencies when both antennas arelocated on the surface of the earth (as is often thecase in standard broadcasting) the total received fieldis given by the Norton surface wave. Thus, the Nortonsurface wave completely determines the primary serv-ice area of a medium -frequency broadcasting station.

The propagation of the Norton surface wave is pri-marily dependent on three parameters: the frequency,the electrical properties of the earth, and the wavepolarization. If these parameters are known, the totalfield induced by the Norton surface wave may becalculated to a high degree of accuracy. In practice,the frequency and wave polarization are known, butthe electrical properties of the earth are a combinationof complex quantities which, in the absence of meas-urements, can only be estimated.

Electrical Properties of Earth

The electrical properties of the earth may be ex-pressed by three constants: the relative permeability,the dielectric constant, and the conductivity. The rela-tive permeability is regarded as unity, and it remainsto determine the dielectric constant, e, and the con-ductivity, a. These two constants influence ground -wavepropagation as expressed in the equation for the com-plex dielectric constant relative to a vacuum. The rela-tive importance of the two constants depends on theradio frequency. Although the values of e and u tendto vary together, exact solutions to the surface -waveequations show that at medium frequencies the con-ductivity has a larger influence on the field strength.At high frequencies, c and o have comparable effectson the field strength. At microwave frequencies theinfluence of the dielectric constant predominates, andthe conductivity is of negligible importance.

The dielectric constant of free space is denoted bye. The value for seawater is 80co, and for ice it is ap-proximately 2e,; average values for land surfaces varyfrom approximately 5r to 30e. A mean value of thedielectric constant relative to free space of (e/e) = 15for all land areas, and (e/e0) = 80 for all water areas,can therefore be assumed in determining the primaryservice area of a medium -frequency broadcast station.

The importance of surface conductivity and fre-quency is illustrated in Fig. 1. Curves are shown forlow (550 kHz) and high (1600 kHz) frequencies inthe standard broadcast band. The curves are plottedas functions of distance and attenuation relative tofree -space inverse distance for conductivities of 1

mmho/m and 30 mmhos/m for both frequencies. Allvalues of conductivity are given in MKS units (milli -

October, 1967 21

0

10

20

30

40

50

60

701

- .- -_,...-.. -,

-.. 0- = 30 mmhos/m 550 kFtz

..... \ ..,\\\\\-.......\\

N \ \N

NN

N

\\ \ \\

N\\\\cr =\\I mmho/m

1

\1600 kHz

(E/E01.15 \NN

N

550 kHz

\ \\

\ 1600 kHz

2 3 5 10 20 30 50 100

DI STANCE IN KILOMETERS

200 300 500 1000

mhos per meter, abbreviated mmhos/m). The attenua-tion above the inverse -distance field strength was de-termined from exact solutions to the surface -waveequations, based on the assumption of a completelyhomogeneous earth, i.e., the dielectric constant andconductivity were assumed to be constant and uniformover the entire path.

Wave Polarization

Wave polarization is very important in medium -frequency broadcasting, especially in the propagationof surface waves and of long-distance sky waves inlow -latitude areas. The presence of a conducting earthsuppresses the propagation of horizontally polarizedsurface waves due to the cancellation effects betweenthe parallel electric vector and the induced groundcurrents. With vertical polarization, the induced groundcurrents serve to restore or reinforce the surface wavein such a way that, for a perfectly conducting planeearth, the field strength at short distances will be equalto twice the field strength in free space. For the sameconditions, the field strength of a horizontally polarizedsurface wave may be 80 to 100 dB below that of avertically polarized surface wave. Therefore, verticalpolarization is used exclusively by all medium -frequencybroadcast stations.

Fig. 1. Attenuation curves show theimportance of surface conductivity.

The Importanceof Ground Conductivity

To determine the service area of a broadcast station,some knowledge of the ground conductivity is essential.From the data in Fig. 1, it can be concluded that it isinsufficient to classify the conductivity in broad descrip-tive terms, such as good, fair, or poor. or in broaderterms such as a single value for all land areas. Thesegeneral classifications may be sufficiently accurate forsome administrative purposes, but indiscriminate usagefor technical evaluation can result in errors of hundredsof square kilometers in the predicted total area receiv-ing primary service. Alternatively, their use for esti-mates of field strengths at specific locations may givevalues which could be ± 20 dB in error. Therefore, aneed remains to devise some method whereby morereliable estimates of conductivity can be assigned tospecific areas.

The decrease in the field strength due to the spread-ing of radio waves with distance can be computedsimply, since the field strength is inversely proportionalto the distance from the transmitting antenna. This lossis represented graphically in Fig. 2 as a pair of adjacentscales with the inverse -distance attenuation (relativeto the field at 1 km) in decibels opposite distance inkilometers.

8

DISTANCE IN KILOMETERS

8

INVERSE DISTANCE ATTENUATION IN DECIBELS

RELATIVE TO THE FIELD STRENGTH AT ONE KILOMETER

Fig. 2. This nomograph can be used to determine the attenuation due to spreading waves (inverse -distance loss).


Fig. 3. Curve relates attenuationwith ground conductivity values.

30

25

20

15

10

5

0

I I I I I

FREQUENCY - 1600 kHz

DI STANCE - 160.9 km

10 20 30 40

ATIENUATI ON ABOVE INVERSE DI STANCE IN DECIBELS

50

Since it is obtain the exact conductiv-ity of a particular area, the total range of earth con-ductivities has been divided into three groups: 0 - 3,3 - 10, and 10 - 30 mmhos/m. Seawater, having aconductivity of approximately 5000 mmhos/m, hasbeen considered separately. The field strength (as cal-culated by Norton [5, 6, 10] and Bremer [11]) as afunction of conductivity and dielectric constant for aspherical earth as shown in Fig. 3, was taken as atypical case for determining the number and range ofthe groups. The conductivities chosen to represent thegroups were 1.5, 6, and 20 mmhos/m. As mentionedabove, a mean value of the dielectric constant wasassumed, i.e., 15e,, for land areas and 80c,, for waterareas. These conductivities were used in calculating theattenuation as a function of distance and frequency.Using Fig. 3 and similar curves for other frequenciesand distances out to 300 km, the greatest possibleerror within any range would be 8 dB above or belowthe field strength calculated, using the reference con-ductivities.

The nomographs presented in Figs. 4 through 7relate frequency and distance to attenuation aboveinverse distance for each of the four groups of con-ductivies. Normally the frequency and distance will beknown, and with a straightedge on the proper nomo-graph, the attenuation in decibels can be obtained. Itmust be emphasized, as discussed above, that the useof these nomographs to calculate the field strength ofthe Norton surface wave is based on the assumption ofa smooth spherical earth that is homogeneous and uni-form in all respects.

Penetration Depth of Ground Waves

The electrical properties of most of the earth (expectseawater and certain land areas, e.g., large deserts) arevery nonuniform. This inhomogeneity exists not onlyhorizontally across the ground, but vertically in depth,and further complicates any method of conductivityspecification.

Vertical stratification of the earth, where differentlayers have different electrical properties, affects thepropagated ground wave, since the electromagneticenergy at different frequencies penetrates to differentdepths. Table 2 shows the relative penetration depthsfor various frequencies and conductivities. These valueswere calculated on the assumption of maximum cur-rent density at the surface and an exponential decreasewith depth. The depths tabulated are those values wherethe current density has decreased to approximately 37%of its surface value; this depth is called the skin depth.

It is apparent from Table 2 that low frequenciesand low conductivities involve penetration depths whichare usually below the surface agricultural soils. Con -

TABLE 2. Penetration Depths

Frequency

(kHz)

Penetration Depth in Meters

Conductivity (mmhos/m)

1 3 10 30

100 46 28 17 10

500 20 11 7 4.5

1000 15 8.5 5 3

1500 12 7.5 4.5 2.5

October, 1967 23

talk about systems...

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October, 1967Circle Item 9 on Tech Data Cord 25

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LtCONDUCTIVITY RANGE

0-3 MMHOS/M

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100 57- 40(E/E.:.) = 15 1300

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15 .4z 900

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1.5 Fig. 4. Frequency -distance -attenua-1 550 tion nomograph for 0-3 mmhos/m.

versely, the surface soil may be most important athigh frequencies if the conductivity is high, or againof lesser importance at low conductivity since the en-ergy will penetrate to greater depths.

Effective Values of ElectricalProperties of the Earth

As previously mentioned, theoretical solutions of theNorton surface -wave field strength are determined asif the earth were homogeneous and uniform. Therefore,the accuracy of the calculations depends on the ac-curacy of the input values of the electrical propertiesof the earth, i.e., its conductivity and dielectric constant.It is neither practical nor necessary, in most applica-tions, to specify or determine the absolute conductiv-ity and dielectric constant for all surface areas; instead,average or apparent values are determined and definedas the "effective" conductivity and "effective" dielec-tric constant. In this context, the "effective" electricalproperties are not true constants of the material, andtheir use is valid only within a limited frequency range.

The "effective" conductivity (ffert) is the conductivityof a uniform homogeneous earth which would havethe same effect on a propagated electromagnetic waveas that of a real earth. For certain areas, as in the caseof a completely seawater path, the effective conductiv-ity is equal to the actual conductivity; values may beassigned and the field strength calculated accurately.

For computing a complex attenuation functionneeded in the classical formulas, the effective dielectricconstant (ceff) must be considered together with theeffective conductivity (creff)

Which Determinethe Effective Ground Conductivity

The importance and influence of a finitely conductingearth upon the propagated surface wave was recognizedmore than 50 years ago by Sommerfeld (12), but verylittle was published concerning the actual values of theearth's electrical properties until the early 1930's. Sincethat time many measurements have been carried out,and publications have been issued which describe themethods of measurement and report values of the ef-fective conductivity in limited areas.

Several of these published reports give estimates ofthe effective conductivity in very small ranges (i.e., I,2, 4, 8, 15, and 30 mmhos/m) for large areas such asthe United States (13, 14), South Africa (15), andCanada (16). While the estimated values for thoselimited areas having measurements are probably reli-able, there are vast areas without measurements wherethe values for these small ranges are doubtful becausethey were based on a rough correlation between theavailable measurements and broad classifications ofsurface soil types. Little or no attention was given tothe influence of any other factors.

In other areas, such as the British Isles (17) andNorway (18), conductivity estimates were based on acorrelation between measurements and soil types, butwere extended to include the effects of subsurfacegeological-lithological formations. In Africa (19), ef-fective conductivity estimates for the MF range werebased solely on surface vegetation for all land areasexcept for those given above for South Africa (15).


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Fig. 5. Frequency -distance -attenua-tion nomograph for 3-10 mmhos/m.

The effective ground conductivity is dependent uponthe relationship of many factors, the most importantbeing the type, thickness, and condition of soils androcks; the type of vegetation; the terrain roughness andland -water features; and to a lesser extent the climate.To understand the significance and relationship of thesefactors on the effective conductivity, it is necessary tostudy the electrical conduction of earth materials (rocksand soils), as well as the geophysical environment ofthe earth.

The principal factor which determines the conduc-tivity of rocks and soils is their resistivity. The resistiv-ity of dry earth materials can he easily measured in thelaboratory (20). Under natural conditions, however,the resistivity is very much dependent on the watercontent, salinity, and in a complicated way on the man-ner in which the water is distributed throughout thematerial (21 ). This condition can only be sustainedin its natural environment.

Geophysical environment factors include the studyof lithology. geologic age, earth structure, temperature.climate, and vegetation.

All of the above factors are important in estimatingthe effective conductivity for a particular area, but therelative importance of each factor is not known, andmuch important information is not available for manyareas. The attenuation due to vegetation, e.g., heavyforest or jungle, is so great that useful ground wavesare limited to very short distances (22 ). Areas of high -density ice and snow would have low effective con -

55

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ductivity values and therefore high signal attenuations.Mountainous regions, considered in the category of

terrain roughness, have low effective conductivities due,in part. to their geological-lithological structure. In

addition, the height of the mountains may be on theorder of several wavelengths when compared to theradio frequency, which causes further attenuation.Therefore, the influence of both roughness and geologi-cal-lithological factors on surface waves propagatinginto or over mountainous regions would be expected.In the medium -frequency range. the relative importancebetween these two factors in not known and requiresfurther study.

The effective conductivity maps referred to forCanada and the United States were prepared and areissued by the Canadian Department of Transport (16),and the Federal Communications Commission ( 14).Copies of the maps may be obtained from the Tele-communications and Electronics Branch, Departmentof Transport, Ottawa, Canada, and the Federal Com-munications Commission. Washington. D.C. Measure-ments taken in many new areas have becomeavailable since these maps were prepared. Theseindicate serious discrepancies between the assumed andactual values for the narrow conductivity ranges used.In addition, since the maps were prepared by inde-pendent governments without exchange of information.discontinuities exist at the international boundary.These are not important, however. when the broaderconductivity ranges of the nomographs are used.

October, 1967 27

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300

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Zr3LAI cip

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CONDUCTIVITY RANGE

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(e/c.),- i5

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Ground -Wave PropagationOver Mixed Conductivity Paths

If the effective conductivity for the entire path is afixed value within the specified range, the attenuationfor the Norton surface wave can be calculated, asshown by the nomographs in Figs. 4 through 7. As isevident from effective conductivity maps published forcertain areas (14, 16), there will be many situationswhere the surface wave will traverse a path over whichthe effective conductivity changes from one range tothe next higher or lower. In this case, a mixed pathexists, and some method of calculation is necessary toaccount for this decrease or increase in attenuation.

There is no known theoretical solution to the prob-lem although some progress is being made (23). Theempirical methods for a solution to this mixed -pathproblem, developed by Eckersley (24), Millington(25), and Somerville (26), now receive widespreaduse. Perhaps the best-known method is that of Milling-ton, although the Somerville method described by Kirkeand called the equivalent -distance method is used inthe United States (4). The Millington method is theonly method which meets the criteria of reciprocity,i.e., the transmitter and receiver may be interchangedand the same result is obtained. Also, it shows betteragreement with theoretical results and practical ob-servations.

The Millington method involves two calculations,

Fig. 6. Frequency -distance -attenua-tion nomograph, 10-30 mmhos/m.

one in the forward direction (i.e., the normal path) andone in the reciprocal direction (i.e., interchanging thetransmitter and receiver locations). The geometric mean(arithmetic mean when the attenuation is given in deci-bels) of the two calculations is then the correct estimateof attenuation.

As an example of the use of this method, supposeit is desired to determine the attenuation above theinverse -distance attenuation at 1000 kHz for a 200 -kmpath composed of an effective conductivity in the range10-30mmhos/m for the first 80 km and 0-3 mmhos/mfor the remaining 120 km. Using the appropriate nomo-graphs of Figs. 4 through 7, the computation is per-formed as follows:Forward Direction:

Atten (80 km at 10-30 mmhos/m) = + 9 dBAtten (80 km at 0-3 mmhos/m) = + 34.2 dBAtten Difference = 9 - 34.2 = - 25.2 dBAtten (200 km at 0-3 mmhos/m) = + 44.7 dBTherefore atten (200 km mixed path)

= 44.7 - 25.2 = 19.5 dBReciprocal Direction:

Atten (120 km at 0-3 mmhos/m) = + 38.2 dBAtten (120 km at 10-30 mmhos/m) = + 12.9 dBAtten Difference = 38.2 - 12.9 = + 25.3 dBAtten (200 km at 10-30 mmhos/m) = 19 dBTherefore atten (200 km mixed path)

= 19 + 25.3 = 44.3 dBThus, the reference attenuation for this path is the


Fig. 7. Frequency -distance -attenua-tion nomograph for 5000 mmhos/m.

300

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CONDUCTIVITY OF SEA WATER

5000 MMHOSIM

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i1200

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't =, 1100

o a1000

900

7 800

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arithmetic mean of the forward and reciprocal attenua-tions, and is 31.9 dB.

According to the equivalent -distance method, theattenuation at 200 km for the mixed -path exampleillustrated above is approximately 5.5 dB greater thanthat computed by the Millington method.

Sky -Wave PropagationThe area defined as the secondary -service area of a

medium -frequency broadcast station receives this ser-vice by reflections from the ionosphere. A brief descrip-tion of some of the physical properties of the ionosphereand the propagation characteristics of MF sky wavesfollows.

The Ionosphere

The ionosphere is a region of ionized gases whichsurrounds the earth. It is composed of gas moleculesand atoms from which electrons are detached by ultra-violet light or X-rays from the sun, or by high-speedelectrons or protons released from the Van Allen belts.The sun is the greatest single source of these high-energy particles, and thus tends to control the state ofionization within the ionosphere. For convenience, theionized region of importance to radio propagation isdivided into four layers, according to height and in-tensity; these are called the D, E, F1, and F2 layers.They are not, however, distinctly separated layers, butrather overlapping regions of ionization which vary inthickness from a few to hundreds of kilometers. Ashallow, or region of lower density. is sometimes evident

between the E and F1 layers. The number of layers,their heights, and their electron density vary from hourto hour, day to day, month to month, season to season,and year to year. In the presence of the earth's magneticfield, the ionosphere acts as a birefringent medium.

The electron density and its variation with time arethe most important properties of the four layers forradio communication. The radio frequencies reflecteddepend on the density; the higher the density of a layer,the higher is the frequency of waves it will reflect. Themaximum radio frequency which is reflected from eachof the four layers is called the critical frequency of thelayer; higher frequencies penetrate the layer. Changesin the ionosphere are detected primarily by shifts inthe critical frequencies which indicate increasing ordecreasing electron density.

The secondary service area of a medium -frequencybroadcasting station is determined primarily by the Dand E regions. The F region may be important whenthe critical frequency of the E layer falls to a lowvalue and the propagation path is relatively short.

Since the radiation effects from the sun exert thecontrolling influence on the electron density within eachregion, the highest critical frequencies are present dur-ing daylight hours. While D -region ionization is usuallyinsufficient to support the reflection of radio waves inthe medium -frequency range, it does cause considerableabsorption of the penetrating waves.

Absorption is the process whereby part of the waveenergy is dissipated by collisions of the excited elec-trons with molecules of air. The wave sets the electrons

October, 1967 31

in motion, and in the absence of collisions the energyis reradiated and restored to the wave. In the presenceof collisions, the ordered motion of the electrons is

destroyed before or during reradiation, and the energyfrom the wave takes the form of thermal energy of theelectrons or thermal (electromagnetic) noise.

Absorption that occurs below the level of reflection,and thus mainly in the D region, is called nondeviative.A second type of absorption important to radio prop-agation is called deviative absorption; it occurs nearthe level of reflection or wherever there is a markedbending of the wave. As the wave nears its reflectinglevel, there is a slowing down or retardation effectwhich allows sufficient time for appreciable absorptioneven though the collision frequency may be low.

The normal daytime level of ionization in the Dregion results in almost total absorption of medium -frequency waves. At night, however, most of the ioniza-tion in the D region disappears, and medium -frequencywaves are propagated long distances with relativelylittle absorption. The reader is referred to a recentpublication of the Department of Commerce, entitledIonospheric Radio Propagation, by Dr. K. Davies, formore information (27).

Sky -Wave Field Strengths

The sky -wave field strength from a medium -fre-quency broadcasting station has a marked increasefrom day to night because of the reduction in iono-spheric absorption. This increase begins near sunsetand reaches a maximum value near midnight local time.Near sunrise, the absorption effect of the D regionbegins, and the field strength decreases rapidly to itslow daytime value.

Daytime sky -wave fields are of negligible importancein medium -frequency broadcasting, since they are ofinsufficient strength to overcome the limitations due toatmospheric noise. Occasionally, however, daytime sky -wave field strengths may be sufficient for practicaloperation at moderate distances beyond the ground-wave range, if high transmitter powers are used andlocal radio interference and atmospheric noise condi-tions are favorable.

Nighttime sky -wave fields are of sufficient amplitude,even with moderate transmitter powers, to overcomenormal noise limitations out to distances of 2000 kmand beyond.

Factors Affecting Signal Strength

Ionospheric absorption is only one of several factorswhich affect the loss of power in medium-frequencysky -wave transmissions. The main sources of powerloss are:1. Equipment mismatch losses,2. Antenna radiation losses,3. The spatial or distance loss due to the spreading

of the wave,4. Ionospheric absorption,5. Multipath interference losses (fading),6. Polarization coupling losses,7. Losses or gains caused by defocusing or focusing

in reflection from a curved or wavy ionosphere.Some of these losses may be determined readily, as,

for instance, those due to 1, 2, and 3, which also applyto ground waves. The others are not easily ascertained,and, in fact, some are not necessarily net power lossesbut involve a redistribution. If recognized, some ofthese losses may be substantially reduced or completelyovercome by employing appropriate techniques. As anexample, a propagated radio wave of any polarization,upon entering the ionosphere, involves a redistributionof energy into two components called the ordinary andextraordinary waves. This redistribution of energydepends on the magnetic dip latitude, propagation di-rection, frequency, and transmitting -antenna polariza-tion. The extraordinary wave tends to be almost totallyabsorbed and thus is of little use for any communicationpurpose. In middle latitudes, the energy distributionbetween the two component waves tends to be ap-proximately equal, while in low latitudes unequal en-ergy distribution may take place, which for certainconditions can result in substantial losses. Again, focus-ing involves a redistribution of power flux over theground so that a decrease in one area is balanced bya greater concentration elsewhere.

Characteristics of theLong -Term Variations ofSky -Wave Field Strength

The received sky wave is composed of a numberof component waves of different amplitudes and phases.The amplitude of the resultant wave is the vector sumof these components. Fading results as the componentsarrive in and out of phase. Long-term variations arerelated to the 11 -year sunspot cycle, the season, thenocturnal hour, and the variations of terrestrial mag-netism. Long-term recordings of sky-wave transmis-sions throughout the band are used to derive semi -empirical formulas for the relationship between theabove factors and the median sky -wave field strength.If sufficient measurements are taken, it is possible topredict, with a certain reliability, the cumulative dis-tribution of sky -wave field strengths for the entiremedium -frequency band. Such quantitative estimatesof propagation characteristics help to determine howwell a broadcast station will meet requirements forsatisfactory service.

Propagation curves of the sky -wave field strengthas a function of frequency and distance for any per-centage of the nights in a year, or any other long period,have been derived from long-term measurements ofmedium -frequency broadcasting stations (28).

Primary Ground -WaveService Limited by Sky -Wave Interference

Because of interference effects, the presence of thesky -wave reflected from the E layer after sunset con-siderably limits ground -wave coverage. If the ratiobetween the sky -wave field strength and ground-wavefield strength, as well as the phase angle between thetwo waves, were constant, the resultant magnitude ofthe received signal would be constant. Of course, ifthe ground -wave and sky -wave signals were of equalamplitude and 180° out of phase, the resultant ampli-tude would be zero. Since the sky wave is not constantin amplitude or phase, the resultant signal exhibitsirregular variations, called fading.


Fading may be manifested either as selective fading,group fading, or a combination of both. Selective fad-ing occurs when the carrier and sidebands do not fadein unison. It may produce severe distortion of the signal.Group fading, in which the amplitudes of the carrierand sidebands fade together and phase relationships aremaintained, does not distort the signal, and so consti-tutes a problem only if noise or interfering signals arestrong. During nighttime hours, selective fading is oneof the important factors in limiting coverage at mediumfrequencies.

This reduction in the primary service area at nightmay be estimated by determining the distance at whichthe predicted median sky -wave field strength is equalto the calculated ground -wave field strength. This rep-resents an approximate limit of the primary servicearea for any particular broadcasting station, and inactual practice would involve a range of distances dueto the variability of the many factors which influencethe sky -wave field strength.

The vertical polar diagram of the transmitting an-tenna is important in the determination of the rangein which interference between the ground wave andsky wave occurs. Base -fed vertical antennas of differentelectrical heights have different vertical polar diagrams.Radiation at the high vertical angles decreases withincreasing antenna length up to approximately 0.5wavelength. On the assumption of sinusoidal currentdistribution and operation over a perfectly conductingplane earth, the optimum vertical antenna length is ap-proximately 0.5 wavelength for maximum primaryground -wave service range.

The use of two or more vertical radiating elementsarranged in some geometrical configuration and excitedelectrically produces radiation patterns which increaseor decrease the radiated energy in both the horizontaland vertical directions. This configuration is called adirectional antenna. Directional antennas have receivedwidespread use in medium -frequency broadcasting fortwo important reasons:1. To direct the radiation to heavily populated areas

and away from sparsely populated areas.2. To provide mutual protection to other cochannel

or adjacent -channel stations for a more efficientutilization of the medium -frequency band.

Standardized optimum designs exist which have beenshown in practice to perform with a very high degreeof approximation to the theoretical maximum. In spec-ified directions and dependent on the number of ele-ments and their configuration, gains of 3 to 9 dB inthe horizontal plane may be realized over a single -element antenna.

Minimum Field Strengthsfor Satisfactory Broadcasting Service

The determination of what constitutes a satisfactorysignal in the absence of station interference involvesan evalution of the atmospheric noise levels to be ex-pected, the levels of man-made noise in cities andtowns, and finally the determination of a satisfactoryacceptance ratio for a broadcast service.Atmospheric Noise

Extensive atmospheric -noise data on a world-wide

basis have been compiled, and reliable estimates of thenoise level with which a wanted signal must competemay be determined for any specific area. Atmosphericnoise varies with frequency, time, and geographic lo-cation. The highest values are encountered during thesummer evening hours (1600-2000 LMT) in all geo-graphic latitudes. The lowest values occur during thewinter morning daytime hours (0800-1200 LMT). Forany season and time period, notice must be taken of thevariability of noise field strength. For instance, duringthe summer evening hours the difference between thenoise field strength exceeded 10% and 50% of thetime may be as high as 17 dB (29).

Man -Made Noise

In many locations, man-made noise is a more limit-ing factor than atmospheric noise for at least part ofthe time. Man-made noise may arise from any numberof sources, such as power lines, industrial machinery,ignition systems, etc., with widely varying characteris-tics. In general, cities or towns have the highest man-made noise levels, although isolated rural areas mayhave high levels due to the proximity of high -voltagepower lines. The noise level within cities or towns varieswidely between industrial, commercial, and residentialareas. Curves showing the man-made noise level forthese areas, similar to the atmospheric -noise curves,are not available. However, reasonable estimates ofthe minimum acceptable ratio to insure satisfactorybroadcast service have been made from limited surveys.

Signal -to -Noise Ratios

The ratio of necessary RF carrier signal to the me-dian hourly rms value of atmospheric noise is approxi-mately 40 dB at the limit of the specified service area.This value is based on a number of measurements un-der the steady-state conditions required for 90% listenersatisfaction. The value is dependent on receiver char-acteristics, mainly the bandwidth, but is representativefor the most common types of broadcast receivers inuse, i.e., a bandwidth of 5 kHz and a minimum op-erating sensitivity of 36 dBu (30). (The abbreviationdBu indicates dB relative to I p.V/M.)

Recommended Minimum Valuesof Field Strength for theSpecific Grades of Service

Two grades of service for medium -frequency broad-casting are the primary service and the secondary serv-ice, both as defined previously. The recommendedvalues of field strength necessary to provide theseservices are (4):Primary Service (ground wave)

City or town business -industrial areas 80-94 dBuCity or town residential areas 66-80 dBuRural areas 40-60 dBu

Secondary Service (sky wave)Rural areas only 54 dBu 50%

of the timeSatisfactory secondary service cannot be rendered tocities or towns unless the sky -wave field strength ap-proaches in value the ground -wave field strength re-quired for primary service. The recommended valuesfor primary service to rural areas as a consequence of

October, 1967 33

atmospheric noise are subject to wide variation depend-ing on the geographic location, season, and time of day.

International Rules and ProceduresGoverning Medium -Frequency Broadcasting

There are no uniform international rules and regula-tions governing medium -frequency broadcasting. Es-tablished practices, however, have led to a somewhatuniform procedure that is followed on an internationalbasis.

Broadcasting in North America

Medium -frequency broadcasting in the United Statesis governed by strict rules and regulations set forth bythe Federal Communications Commission. Almostidentical rules and regulations have been adopted byseparate international treaties between the United Statesand Mexico, Canada, Cuba, Dominican Republic, andthe Bahama Islands.

By these treaties, the 107 channels within the band535 to 1605 kHz have been divided into the followinggeneral classes:Clear channels-Reserved for those stations which areintended to render service over wide areas free of ob-jectionable interference within their primary serviceareas and over all or a substantial portion of theirsecondary service areas. Clear -channel stations arelimited to maximum power of 50 kw, except for cer-tain channels assigned to Mexico.Regional channels-Reserved for those stations thatoperate with powers not in excess of 5 kw and renderonly a primary service. Stations operating on regionalchannels do not have secondary service areas, and theprimary area at night is limited by sky -wave interferencefrom cochannel stations.Local channels-Reserved for those stations which op-erate with powers not in excess of 1 kw daytime and0.25 kw nighttime. The primary service area of a sta-tion operating on any such channel may be limited asa consequence of interference. Local -channel stationsdo not have secondary service areas, and the primaryservice area at night is limited by sky -wave interferencefrom cochannel stations.

Broadcasting in Central and South America

Most countries within this region are members ofthe International Telecommunications Union, which hasadopted general rules and regulations pertaining to me-dium -frequency broadcasting. In most instances, agree-ments between adjacent countries are made on a case -by -case basis to prevent undue interference betweencochannel and adjacent -channel assignments.

In general, stations with high transmitter power arerequested to use the following assignment plan:1. Channels in the low end of the band when only theground -wave service area is to be served.2. Channels in the upper end of the band when it ischiefly a question of serving the sky -wave service area.3. Intermediate channels when both the ground -waveservice area and sky -wave service area have to beserved.

There are no international restrictions on transmitter

power, and a number of stations throughout the worldoperate with powers in excess of 1000 kw.

Several countries within Central and South Americahave adopted internal frequency -assignment plans whichassign certain medium frequencies to classes similar tothose adopted by the North American countries. How-ever, the channels assigned for a specific class do notnecessarily follow the recommendations of the ITU.

Concluding Remarks

The nomographs presented and the effective -conduc-tivity maps referenced, may be used for the calculationof the primary service area or field strength from astandard AM broadcast station operating in the me-dium -wave band out to a distance of 300 km. This dis-tance is the approximate limit of primary service to ur-ban and rural areas provided by moderate -power (5 to10 kw) standard AM broadcast stations, depending, ofcourse, on the frequency, antenna, and intervening pathconductivity.

At night, interference from the station's own sky wavereduces the effective ground -wave (primary) service todistances much less than those obtained during daytimehours. This report describes the physical process caus-ing this reduction in service and the availability duringnighttime hours of a good -quality broadcast service pro-vided by the sky -wave field to distances far beyond themaximum ground -wave range.

Values of field strength derived from the graphsshould be considered only as estimates pending furtherstudy of the effective -conductivity maps used to definethe surface conductivity for this frequency range. A

Sample Computation

As an example of the use of the nomographs andmaps in this article, the primary service provided bya typical AM broadcast station will be computed.

Broadcast frequency assignments may be obtainedfrom the IFRB-ITU list. This list, published yearly,shows all notified assignments by frequency, settingforth the city and country, transmitter power, geo-graphical coordinates of the transmitter, and hours ofoperation. Other listings are published regularly byprivate organizations and official government agenciesfor the particular government concerned, such as thelisting published by the FCC entitled, "Official Listfor Information Setting Forth Notified Assignmentsof Standard Broadcast Stations of the United States."Similar lists are available for Canada, Mexico, andmost Central and South American countries.

This example will be based on a station operatingas follows:

Frequency:Transmitter power:Hours of operation:Polarization:Antenna height:

590 kHz5 kw

Unlimited.Vertical140 m above ground(99.5 electrical degrees)

A lossless, short vertical dipole operating over aperfectly conducting plane earth will radiate a fieldstrength in the horizontal plane equal to 300 mv/m


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ITTOctober, 1967 Circle Item 11 on Tech Data Card 35

450

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350ce

ccO-H

300

:71

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2000 40 80 120 160 200 240

HEIGHT OF VERTICAL ELEMENT IN ELECTRICAL DEGREES280

at 1 km for 1 kw of transmitter power. The theo-retical radiation at 1 km for other vertical antennasup to 0.76 wavelength in height is shown in Fig. 8.Measurements have shown that these theoreticalvalues are attained for vertical antennas above aboutone -quarter wavelength in height if suitable groundscreens are used at the base. The main purpose ofground screens is to reduce the ground losses ofcirculating currents in the immediate vicinity ofthe antenna. Grounded vertical antennas less than0.25 wavelength (90 electrical degrees) have largebase currents and consequently have higher losseswhen operating over an imperfectly conductingearth. Therefore, short vertical antennas requiregood ground systems if reasonable efficiencies areto be obtained. As an example, the field strengthat 1 km for a 0.125 -wavelength (45 electrical de-grees) vertical antenna at 1000 kHz without a groundsystem will be approximately 150 my/m, or 6 dB lessthan that obtained for a perfectly conducting planeearth; the earth's effective conductivity is assumed tobe 10 mmhos/m. A ground system consisting of 120equally spaced copper wire radials from the antennabase, 0.25 wavelength long, will provide a radiatedfield within 2 dB of the theoretical maximum.

For the subject station, the height of the antennais 99.5 electrical degrees (0.276 wavelength), andFig. 8 indicates this antenna will radiate a fieldstrength of 315 mv/m for 1 kw or 704 mv/m for 5kw (315 X -\j) at 1 km. This corresponds to 117dB above 1 p.v/m (dBu).

The estimated effective conductivity for the vicinityof the station is in the range 10-30 mmhos/m, andthe nomograph of Fig. 6 corresponding to this rangeshould be used for all computations.

Fig. 8. Field strength at one mileis dependent on height of tower.

It is desired to know the expected field strength ata distance of 100 km. From Fig. 2 the inverse -distance attenuation is found to be 40 dB, and fromFig. 6 the attenuation above inverse distance is 3.5dB. Therefore, the field strength at 100 km from thisstation, operating with a power of 5 kw on 590 kHz,is 43.5 dB below the unattenuated field strength (117dBu) at 1 km, or 73.5 dBu (117 -43.5). This valueis well above the minimum required for satisfactoryreception in city or town residential areas during day-time hours, but may be limited to a higher value atnight due to sky -wave interference from cochannelassignments.

References

1. Norton, K. A. and L. Gainen. A Study of the Geograph-ical Distribution of Population on the Coverage Obtain-able from a National Television System. Ad Hoc Com-mittee for the Evaluation of the Radio PropagationFactors Concerning the Television and Frequency Modu-lation Broadcasting Services in the Frequency RangeBetween 50 and 250 Mc, October 1950.

2. Kirby, R. S. "Measurements of Service Area for Tele-vision Broadcasting," I. R. E. Transactions on BroadcastTransmission Systems, PGBTS-7 (February 1957),23-30.

3. Measurement of Field Strength for VHF (Metric) andUHF (Decimetric) Broadcast Services, Including Tele-vision, CCIR Report 228. Geneva: ITU, II, 1963.

4. FCC. Rules and Regulations, Vol. III, Pt. 73, RadioBroadcast Services. Washington, D.C.: Supt. of Doc.,U. S. Government Printing Office, 1964.

5. Norton, K. A. "The Propagation of Radio Waves Overthe Surface of the Earth and in the Upper Atmosphere,Pt. I," Proc. I. R. E., 24 (October, 1936). 1367-1387.

6. Norton, K. A. "The Propagation of Radio Waves Overthe Surface of the Earth and in the Upper Atmosphere,Pt. II," Proc. I. R. E., 25 (September 1937), 1203-1236.


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October, 1967


37

7. Norton, K. A. "Physical Reality of Space and SurfaceWaves in the Radiation Field of Radio Antennas." Proc.I. R. E., 25 (September 1937), 1192-1202.

8. Norton, K. A. "Space and Surface Waves in RadioPropagation," Physical Review, 52 (July 1937), 132-133.

9. Wait, J. R. "A Note on Surface Waves and GroundWaves," IEEE Trans. on Antennas and Propagation,AP -13 (November 1965), 996.

10. Norton. K. A. "The Calculation of Ground -Wave FieldIntensity over a Finitely Conducting Spherical Earth,"Proc. I. R. E., 29 (December, 1941), 623-639.

11. Bremmer, H. Terrestrial Radio Waves. New York. N. Y:Elsevier Publishing Co., 1949.

12. Sommerfeld, A. "The Propagation of Waves in WirelessTelegraphy" (in German), Ann. der Phys., 28 (March1909), 665-736.

13. Kirby. R. S., J. C. Harman, F. M. Capps, and R. N.Jones. Effective Radio Ground -Conductivity Measure-ments in the United States, NBS Circular 546. Dept.of Commerce, February 26, 1954. (Out of Print)

14. Fine, H. "An Effective Ground Conductivity Map forContinental United States," Proc. I. R. E., 42 (1954),1405-1408.

15. Vice, R. W. "A Survey of Ground Wave PropagationConditions in South Africa," IEE Transactions of SouthAfrica, 45 (April 1954), 139-150.

16. Ireland, G. C. "A Provisional Ground Conductivity Mapfor Canada," Proc. I. R. E., 49 (1961), 1674-1678.

17. Some Measured Ground Conductivities in the BritishIsles and Their Geological Correlation, Research ReportK062, British Broadcasting Corp., 1944/10.

18. Eliassen, K. A. "A Survey of Ground Conductivity andDielectric Constant in Norway Within the FrequencyRange 0.2 - 10 Mc/s." Geofys. Publikasjoner, XIX(1959), 5-30.

19. Report by the Preparatory Meeting of Experts, AfricanLF/MF Broadcasting Conference. Geneva: CCIR, Feb-ruary 1964.

20. Smith -Rose, R. L. "Electrical Measurements on Soilwith Alternating Currents," IEE (British), 75 (1934),221-237.

21. Card, R. H. "Earth Resistivity and Geological Struc-ture," Trans. AIME, 138 (1940), 380-398.

22. Herbstreit, J.W. and W. Q. Crichlow. "Measurementsof the Attenuation of Radio Signals by Jungles," RadioSci. J. Res. NBS, 68D, No. 8 (1964), 903-960.

23. Wait, J. R. and L. C. Walters. "Curves for Ground WavePropagation over Mixed Land and Sea Paths," IEEETrans. on Antennas and Propagation, AP -11 (January1963), 38-45.

24. Eckersley, P. P. "The Calculation of the Service Areaof Broadcast Stations," Proc. IRE, 18 (July 1930), 1160-1194.

25. Millington, G. "Ground Wave Propagation over anInhomogeneous Smooth Earth," Jour. IEE (London),Pt. III, 96 (January 1949), 53-64.

26. Kirke, H. L. "Calculation of Ground -Wave FieldStrength over a Composite Land and Sea Path," Proc.I. R. E., 37 (May 1949). 489-496.

27. Davies, K. Ionospheric Radio Propagation, NationalBureau of Standards Monograph 80, Department ofCommerce. (For sale by the Superintendent of Docu-ments, U. S. Government Printing Office, Washington,D. C. 20402 -Price $2.75)

28. Barghausen, A. F. "Medium Frequency Sky WavePropagation in Middle and Low Latitudes," IEEE Trans.on Broadcasting, BC -12 (June 1966), 1-14.

29. World Distribution and Characteristics of AtmosphericRadio Noise, CCIR Report 322. Geneva: ITU, II,(1963).

30. Performance Specifications for Low -Cost Sound Broad-casting Receivers, CCIR Recommendation 415, Geneva:ITU, V, (1963).

31. IEEE Standards Coordinating Committee 14 (Quanti-ties and Units). "IEEE Recommended Practice for Units

in Published Scientific and Technical Work," IEEESpectrum, 3 (March 1966), 169-173.

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The all solid state BELAR ADD-ON FM MONITORINGSYSTEM allows the broadcaster to fulfill monitoringrequirements as they arise. The basic unit is theFMM-1 Frequency and Modulation Monitor for mon-aural use. When requirements call for stereo, addthe FMS -1 stereo unit to monitor the 19 KC pilotfrequency as well as all the modulation characteris-tics of FM stereo. Add the SCM-1 unit for monitor-ing SCA background music programming as well asremote control telemetering applications. Today'smonitoring requirements make this system a must.

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Additionally, the SM50 is the cleanest sounding profes-sional microphone at anywhere neap its price class. It de-livers highly intelligible, natural and pleasing speech andvocal music that is especially full-bodied and rich in thecritical mid -range.It is extremely rugged and will require little or no down timeas the years go by. Too, when comparing it to other mod-erately priced omnidirectionals, it is lighter in weight,supremely well-balanced for "handability," has a detach-able cable, and a rucoer mounted cartridge for minimizinghandling noises. The SM50 is worthy of your most seriousconsideration.For additional information, write directly to Mr. Robert Carr,Manager of Professional Products Division, Shure Brothers,Inc., 222 Hartrey Avenue, Evanston, Illinois.

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October, 1967 Circle Item 14 on Tech Data Card 39

Engineers' Exchange(Continued front page 6)

because of the possibility of humanerror, the idea was rejected in favorof a unit designed to achieve auto-matic switching. This approach waspossible because burst and othercolor information are transmitted atthe color-subcarrier frequency of3.58 MHz. Consequently, the unitcould be designed to trigger on asubstantial voltage at that frequency.

In order to effect more positiveoperation, not only is the RF sec-tion tuned sharply to 3.58 MHz, buta series crystal filter arrangement is

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included in the input to furthersharpen the response at that fre-quency. The power supply is builtin, and the unit may be coupled intothe video circuitry coming in fromnetwork or any other circuit, eitherbridging or terminating at 75 ohmswith a resistor across the input.

Potentiometer R3 adjusts the in-put to the grid of the relay -amplifiersection of V3, and potentiometerR7 adjusts the bias to the cathodeof the same tube section. Either con-trol could be eliminated, if desired,by experimenting with appropriatefixed resistances for substitution.However, to make the unit as flex-ible as possible in every way, bothwere included in the original ver-sion. The unit will trigger on com-posite signals of from as low as one -quarter volt to as high as desired be-cause these levels can be adjusted.

The cost of all components wasless than $40. The unit can also beused to turn on a warning light,sound a buzzer, or key any otherdevice when a color burst comes on.

-John B. Broughton

Parts List

C1-0.01 mfd, 600 VC2-0.01 mfd, 600 VC3 0.01 mfd, 600VC4-0.05 mfd, 600 VC5-0.01 mfd, 600 VC6-20/20 mfd, 250 V electrolyticC7-50 mfd, 50 V electrolyticC8-50 mfd, 50 V electrolyticC9-0.1 mfd, 600 V

RI, R2-4700 ohm, 1 wattR3 -500K pot, 2 watt; Clarostat 47 -500k -S,

155-93

R4-10 ohm, 1 wattR5-670 ohm, 2 wattR6-100 ohm, 1 wattR7 -500 -ohm pot, 2 watt; Clarostat 53C1 -500-

S, 325-195

Dl, D2 -1N1084 silicon -diode rectifier

T1, T2, T3-Band-pass transformer, 3.58 MHz,RCA 112869

T4-125 V, 50 ma, 6.3 V, 2 amp, Thordarson26R38

T5-12.6 V filament transformer, Triad F -44X

Kl-DPDT Plug-in relay, 5 ma, 10K, Potter &Brumfield Type KCP-11, 217

11-Jack S0-239

F1 -2 -amp slow -blow fuse

S1-SPST line switchTB1-6-terminal stripX1 -3.58 -MHz crystal

Chassis-Aluminum 13" X 41/4" X 25/8"

s4Memorex Corporation, a leader in the develop-ment, manufacture and sale of precision magnetictape, has openings for qualified individualsthroughout the country.You must be an already successful salesman withan extensive background in and thorough knowl-edge of the video broadcast engineering field.You must be looking for more challenge to yourabilities and greater earning potential. To cus-tomers in the video recording industry you will beoffering professional sales service in the form of

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October, 1967Circle Item 15 on Tech Data Card 41

A SYSTEM FOR

SEPARATE REPEATER

ORIGINATION

When Radio Southern Manitobaestablished a repeater station 40miles northwest of the main studiolocation at Altona, Manitoba, analmost entirely new audience wasgained. CFAM (1290 kHz), theoriginal station, covers an approxi-mately circular area around Altona,and CHSM (1250 kHz) coversWinnipeg and an area to the east.The patterns of the two stations areshown in Fig. 1.

Products and services of generalinterest can be advertised on bothstations, but many businesses areconcerned only with their local area.For these concerns, a system wasdeveloped by RSM whereby dif-ferent spots for each area are runat the same time. This permits amore attractive rate structure forthe smaller, local advertiser, and thecommercial potential for the systemis considerably improved. Further,each of the two stations can ac-quire an individual image.

Radio stations CF AM and CHSM,Altona and Steinbach, Manitoba.

by W. H. Lindenbach*Cartridge tape supplies separate commercials toindividual markets of a two -station "network."

System Concept

Commercial spots for the systemoriginate in four cartridge -tape play-back units. Each unit can be usedindividually for conventional play-back through the console as shownin Fig. 2A. The console output,during combined -mode program-ming, is supplied to both transmit-ters via a wire line to CFAM and amicrowave studio -transmitter link(STL) to CHSM.

In the split mode, the console isout of the circuit (as shown in Fig.2B). The cartridge playbacks areconnected directly to the wire linesand the STL. When the switch isup, Cartridge 2 supplies CFAM, andCartridge I supplies CHSM. Withthe switch down, Cartridge 4 sup-plies CFAM and Cartridge 3 sup-plies CHSM.

This arrangement increases ver-satility by making it possible to paira spot with any other of identicallength. Also, with two pairs of play -

CAM 1290MANITOBA AITONA

NONTA DAKOTA

Fig. 1. Map shows coverage of primary station CFAM and repeater station CHSM.

backs, "split" spots may be run"back-to-back", i.e., one after theother, as is often necessary when asplit spot pair is run next to a splitID.

CircuitryThe complete system includes

audio units and circuitry for controland signal routing.

Audio Section

The audio circuit, shown in Fig.3, includes the four cartridge -tapeplayback units, the console, a level -control amplifier, an AGC amplifierwith low-level input, ( -42 VU),six mode -switching relays desig-nated KO1 through K06, and aconnection to the control -roomprogram -monitor system. Terminalsand patch jacks are omitted in Fig.3 for clarity, and the relays areshown in the released conditionwhich results in the combined mode.When all relays are operated, thesplit mode results. K02 is a latchingrelay which is pulsed to select car-tridge units 1 and 2 as Pair I, orunits 3 and 4 as Pair II.

Common Mode. The cartridge -unit outputs are supplied to twoconsole inputs through KO1 and anarrangement of attenuators. Theseattenuators combine two cartridge-unit outputs into one console input.The parallel -connected 15 -dB padsare matched to the console by 10 -dB, 300/600 -ohm taper pads.

The console high-level output issupplied to the center position ofS23, through K05 to the level -con-trol amplifier; the amplifier outputgoes to the CHSM program terminaland on to the STL and CHSM trans-mitter. The level -control amplifieroutput also goes to K04, to a 600/600 -ohm line transformer, and tothe CFAM program terminal. The


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Circle Item 16 an Tech Data CardOctober, 1967 43

CART 1 I--I CART 2

CART 3

CART 4

CONSOLE

(A) Conventional operation

WIRE

TRANSMITTER

CFAA1

CHSMTRANSMITTER

(B) Split -mode operation

Fig. 2. Commercial spots for the system originate in four cartridge units and

8 -dB taper pad at the amplifier out-put matches the two paralleled600 -ohm loads.

The console low-level output(program bus) is supplied to theAGC amplifier input via K03. Thehigh-level AGC output is appliedto the lower position of S23, calledthe "emergency program source"switch, since it can select the out-put of the AGC amplifier or therecording control room in case offailure of the console amplifier.

The monitor signal originates ina conventional CFAM off -air pick-up, which is supplied to the monitorboost amplifier via S24, the monitorselector switch, and to the monitorpower amplifier.

Split Mode. Operation in the splitmode will be considered with pro-gram originating in Pair I: Car-tridge Unit 1 supplying CHSM andUnit 2 supplying CFAM. RelaysKOI, K03, K04, K05, and K06 are

All equipment necessary to system iscontained in console -mounted cabinet.

operated, and K02 is latched in thePair I position.

The output from Cartridge Unit2 (at + 8 VU) is supplied to theoperated contacts of K01, to thePair I contact of K02, and then tothe CFAM VU meter. Then it isbalanced by a 600/600 -ohm trans-former, dropped in level 50 dB, ap-plied to K03, and to the AGC-amplifier input at the correct level.( -42VU). Relay K03 also term-inates the console program -bus out-put in 600 ohms, since the bus isnow disconnected from the AGC-amplifier input. The AGC-amplifieroutput is applied to the CFAM pro-gram terminal through K04 and theline transformer. Contacts on K04also replace the CFAM line -trans-former load on the level -control -amplifier output with 600 ohms.

Output from Cartridge Unit 1

(also at + 8 VU) is supplied to theCHSM VU meter through KO1 andthe Pair I contacts of K02, then toK05 and the level control -amplifierinput. Relay K05 also terminatesthe console high-level output in 600ohms through S23. The level -con-trol -amplifier output is applied tothe CHSM program terminal.

At the CHSM VU meter, outputfrom Cartridge Unit 1 is also sup-plied to a bridging transformerthrough K06. The signal is attenu-ated 40 dB and applied to the com-bining pad, (which is simply twopads with outputs in parallel) andcombined with the off -air CFAMsignal, which is at a level 10 -dBhigher than the CHSM signal. Theoperator can distinguish one fromthe other by adjusting the monitorvolume control in the monitor boostamplifier. When the volume isturned down, he hears the CHSMspot only; when the volume is high,

can be delivered to either operation.

he hears the CFAM spot predom-inantly.

Control Section

There are two identical controlunits-one for each pair of car-tridge units. When the operatorpresses the START push button, thecontrol unit operates all the audiorelays and starts the cartridge units.Two conditions are imposed on thestart function: (a) both cartridgeunits of the pair about to start mustbe loaded with cartridges, and (b)the other pair must not be running.If these two conditions are not met,the control unit does not respondto the START button, thus providingprotection against operator error.

The end of the split -mode periodis signaled by "end -of -message"secondary cue tones recorded on thecartridge tapes. The control unitsenses these cues, and when twohave been received, indicating bothmessages are finished, it releases theaudio relays, returning the systemto the combined mode and permit-ting the other pair to start if andwhen desired.

If the end -of -message cue fails,or if it is necessary to return to thecombined mode immediately, aREVERT push button is pressed. Itsimulates the reception of two end -of -message cues.

Pilot lights provide conditionarysupervision to indicate the opera-ting mode of the system. A greenlight indicates the combined mode,and a red one is illuminated for thesplit mode. One set of these lightsindicates if either of the control -unit cartridge -unit pairs is in thesplit mode. Two amber READY lights,one for each control unit, operatewhen two cartridges are inserted.When a cartridge pair is started inthe split mode, the corresponding


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CENTRAL DYNAMICS CORPORATIONHEAD OFFICE: 903 Main St., Cambridge, Mass. 02139


October, 1967 45

CART 1

PR

0

12°)..t

CART 2

CART 3

CART '4

AUD

CFAM OFF -A I R 0 0 0

PROG 0-2

CFAMVU

CIISMVU

600603

RIF; 50dB

I I

410-

154B

15 dB

15 dB

15 d8

10 dB

3031600 .1

10 d8

3031600

CONSOLE

PROGRAM BUS

10K1600

III

MONITOR BOOST

AMPLI FIER

6001600

40 dB

O 10 dB

COMBINER

0MONITOR POWER

AMPLIFIER

ACC

AMPLIFIER

MICRLEVEL

OUTPUT

RECORD0-4--o CR

PROG

LEVEL -

CONTROL AMP

8 dB

60300600

0

oy

6031603IIOISM

PROGRAM

Fig. 3. Audio circuit includes cartridge units, console, level -control amplifier, AGC amplifier, relays, and connections.READY light goes off and does notgo on again until the pair has re-turned to the combined mode andat least one cartridge has been re-moved and replaced. Thus, theREADY light answers the operator'squestion, "Has this pair of spotsgone on the air yet?" The answeris not always obvious; during a busyperiod it is hard to remember whichpair should be started next andwhich should be reloaded.

Operation

The complete circuit of one con-trol unit is shown in Fig. 4. Relaynumbering indicates location, e.g.,K 12 indicates the second relay inthe Pair I control unit.

Start Relay K 1 1 Operation. Re-

lay K 11 starts the Pair I cartridgeunits, locks run relay K12 into theoperated condition, pulses the PairI coil of audio relay K02, and pro-vides status indication to the READY -

light supervisory circuit.A study of the K 11 coil -control

circuit shows that the coil will notbe energized unless the followingoccur together: (a) the START pushbutton is pressed, (b) K22, the PairII run relay, is released, insuringthat Pair II is not in the split mode,and (c) K13 and K14 are operated.The coils of the latter two relaysare connected so that they operatewhen cartridges are inserted in Car-tridge Units 1 and 2. Relay K 1 1

operates momentarily.Run Relay K12 Operation. Relay

K12 is in a self-locking circuit whichoperates all audio relays exceptlatching relay K02. It prevents PairII from starting when Pair I is inthe split mode, and it supplies volt-age to two end -of -message sense re-lays preparatory to sensing thesecues. When K12 is operated, Pair Iis in the split mode.

If K15 or K16 and K19 are re-leased and K11, the start relay, op-erates momentarily, K12 will oper-ate, and because one of its owncontact sets is in parallel with thestart relay contacts, it will lock. K12will release if both K15 and K16operate together, or if K19 operates.When K12 releases, Pair I returnsto the combined mode.

End -of -Message Cue -Sense Re-


PDT PB -412a

START

SWITCH

POINT "A'

START

INHIBIT

C)

24VDC WHEN fCART 1 LOADED 1

24Y DC WHEN

CART 2 LOADED

TO CART I IREMOTE STARE 1 o

TO CART 2

REMOTE START 1 D

READY

NI

READY SIGNALEND OF MESSAGE

CUE SENSE

FROM END OF MESSAGE

1-.3' }FROMEND OF MESSAGE

CUE. CART 1

CUE CART 2

TO CART 2

REMOTE STOP

Fig. 4. Diagram of one control unit

lays K/5, KI6 Operation. These re-lays are in a self-locking circuit andsense end -of -message cues fromCartridge Units 1 and 2 in order torelease K12 when two cues are re-ceived.

If run relay K12 is operated (PairI in split mode) and an end -of -mes-sage cue is received from CartridgeUnit 2, K16 will lock. As describedunder operation of run relay K12,if both K15 and K16 operate, K12releases, and if K12 releases, K15and K16 release immediately there-after.

Ready Light Control Relays K17and K18 Operation. These relaysprovide a supervisory indication bymeans of the READY light. Onlywhen cartridges have been loaded

shows sequence of relays which control

into the Cartridge Units 1 and 2,and prior to playing in the splitmode, is the READY light on.

Relay 17 has two coils, to whichvoltage is applied with oppositepolarity; if voltage is applied to Coil1 or 2, K17 operates, but if voltageis applied to both coils the relaydoes not operate.

When Cartridge Units 1 and 2are loaded, +24 volts DC appearsat point "A" (Fig. 4), as describedunder "Start Relay KI1 Operation."Coil 1 of K17 is energized throughthe normally closed contacts of K18,and K17 operates, turning theREADY light on.

When run relay K12 is operated(Pair I in split mode) the coil(point "B") is grounded as de -

operation of two tape -cartridge sources.

scribed under "Run Relay K12 Op-eration." Coil 2 of K17 is energizedthrough the normally closed con-tacts of K18; the field of Coil 1 iscanceled, and K17 releases, turningthe READY light off.

When cartridges are inserted inCartridge Units 1 and 2, + 24 voltsDC appears at point "A," but K18can operate only if K15 and K16operate together (two end -of -mes-sage cues received), or if K19, therevert relay, operates. When K18operates, it is locked by a pair ofits own contacts.

Relay K18 operates at the endof the split -mode period; it opensboth coil circuits of K17. Initially,K17 was released because bothcoils were energized with opposite

October, 1967 47

Day or night...WHDH-TVgets great pictures with

"big tube" color cameras

WHDH-TV, Boston, is using four TK-43 "big tube" colorcameras to put an extra wallop in baseball telecasting.Whether during the day - under ideal conditions - or atnight when light levels range from 40 to 120 ft. candles,their color pictures have consistent sharpness and brilliance.

Let's hear how Phil Baldwin, Vice -President, Engineering,WHDH, sizes it up in his own words. "I've never seensharper pictures than we get with our RCA cameras. Thiseven goes for our center field camera at night, whichpicks up all the color and detail of the spectators sittingin the stands behind home plate. You simply can't getsharper pictures."

So pleased are the people at WHDH with their RCA colorcameras that they also have two TK-42's in the studio

and two more TK-43's in a mobile unit now being built- making a total of eight "big tube" cameras. Ten yearsof all -color telecasting back up everything WHDH is doingtoday. Their experience with color proves that where thepicture counts - RCA's got it - with the "big tube"TK-42's and TK-43's.

If you are interested in the very finest color picturesunder a variety of everyday conditions, get the facts onRCA's "big tube" color cameras. Call your RCA Broad-cast Representative. Or write RCA Broadcast and Tele-vision Equipment, Building 15-5, Camden, N. J. 08102.

THE MOST TRUSTED NAME IN ELECTRONICS

Form 3J5182 -A Trademark(s)8 Registered Marca(s) Registrada(s) Printed in U.S.A.

CO/MIMED

SPLIT

+24 TO GNDVDC AUDIO

RELAYCOILS

Fig. 5. Relay controls lamps to showmode in which stations are operating.

polarity; now it remains releasedbecause both coil circuits are open,and the READY light stays off. Re-lay K18 remains locked until + 24volts DC is removed from point "A"by removal of at least one cartridgefrom Cartridge Units 1 and 2, andrelease of K13 or K14. Relay K17remains released because, althoughboth coil circuits can now be com-pleted through contacts on K18,+24 volts DC has been removedfrom point "A" by the release ofK13 or K14, and ground has beenremoved from point "B" when, atthe end of the split mode, K12 wasreleased. Now the cycle can beginagain, with the insertion of twocartridges resulting in the presenceof + 24 volts DC at point "A" andthe operation of K17, which turnson the READY light.

Revert Relay K19 Operation. Ifthe end -of -message cues are not re-ceived at the end of the split -modeperiod, they may be simulated bypressing the REVERT push button,which operates K 19. Two sets ofcontacts on this relay are connectedto the remote stop terminals ofCartridge Units 1 and 2. Other con-tacts operate K18 to keep the READYlight off, and release run relay K12to return the system to the com-bined mode.

Complete Cycle Description.When cartridges are inserted inCartridge Units 1 and 2, K13 andK14 operate. +24 volts DC is ap-plied to K17 Coil 1, and it operatesto turn on the READY light. If Pair

Audio -relay chassis contains relaysand connections to audio circuitry.

II is not in the split mode, K22 willbe released, and the coil circuit ofstart relay K 11 can be completedby pressing the START push button.Relay K 1 1 operates momentarily topulse audio relay K02 into the PairI position, start Cartridge Units 1

and 2, and operate run relay K 12.When K12 operates, it locks,

energizes K17 coil 2 (with polarityopposite to that of coil 1) causingK17 to release and turn the READY

light off, grounds the coils of K15and K16 (end -of -message cue senserelays) readying them for opera-tion, operates all audio relays ex-cept K02, and opens the start re-lay coil circuit in Pair II. Pair I is

now in the split mode, and Car-tridge Units 1 and 2 supply audio tothe two transmitters.

When Cartridge Unit 1 detectsan end -of -message cue. K 1 5 oper-ates and locks; when Cartridge Unit2 detects a cue, K16 operates andlocks. The opposite sequence is pos-sible, but when both are operated,run relay K12 is released, the PairII start -relay coil circuit closes, theaudio relays are released, K15 andK16 are released, and Coil 2 ofK17 is denergized. But, while K15and K16 were operated, K18 op-erated and locked, and both coilcircuits of K17 opened to keep theREADY light off. The 20-mfd ca-pacitor across the coil of K12 is

necessary to slow down the inter-action between KI5, KI6, and K12,so that K18 has time to operate andlock.

Pair I is now out of the splitmode, and Cartridge Units 1 and2 recue their cartridges to the be-ginning of the next spot. When onecartridge is removed, K18 releasesand the cycle is complete.

Mode Supervisory Signaling. Fig.5 shows KC1, the contacts of whichoperate the mode -supervisory lights.The KC1 coil is connected acrossthe audio relay coils so that it op -

Pair I control unit has VU meters forobservation of outputs to stations.

erates when the system ( Pair I orII) is in the split mode, turning offthe COMBINED light and turning onthe SPLIT light.

Using the System

Initially some difficulty was ex-perienced with dust in the audiorelay contacts. All contacts operateunder dry switching conditions andare therefore very sensitive to con-tamination. Replacement of theopen latching relay with an en-closed unit, and periodic cleaningof the contacts of the other audiorelays, prevented further problems.

To minimize switching transients,KOI, K03, K04, and K05 are make -before -break relays.

Access to all circuits via patchjacks proved useful during trouble-shooting. By nature, opportunity toobserve difficulties is short, andmeans for simulating operation isnecessary if programming interrup-tions are to be avoided.

Considerable difficulty was en-countered with instability in theend -of -message cue detector cir-cuitry in the cartridge units. Thecircuit is temperature -sensitive; allelectrolytic capacitors had to be re-placed because of changed values.

It was expected before split op-eration was begun that our greatestdifficulty would be the proper timingof the cartridges that were to runin pairs so that they would finishtogether. However, the announcersfound no difficulty in "reading tothe clock" and maintaining plus orminus one -second conformity in a60 -second spot. Two categories areused together: 30 seconds and 60seconds.

To reduce chances of error dur-ing a busy period, a color codingsystem was developed for cartridgesand cartridge machines.

The cost of parts for the controlunits, power supply, audio relays,and mountings was under $400. A

HriltillieriktdatrEalWitEmaitaelftti

mminimminv

Circuit for Pair II control unit isidentical to that of the Pair I unit.


BBRC/Miratel Brings You...

The Phantom - This is probably the newestand least -known broadcast television color monitor available tothe industry today. It's reliable. It has exceptional color fidelity.

It's priced from $775 to $1275. And it's available off the shelfright now. We think it's the answer to your color

monitor needs. You probably would, too. If you knew moreabout it. A look at our color monitor data sheet, followed by an

evaluation of the MC19 in your operation, will settle that matter.

MIRATEL DIVISION BALL BROTHERS RESEARCH CORPORATION 3600 RICHARDSON STREET NEW BRIGHTON ST. PAUL, MINNESOTA 55112

MIRATEL

Circle Item 18 on Tech Data CardOctober, 1967 51

VIDEO -AUDIO CUEING SIGNALS

CUM CUE 4CIIDATokMOM 00-1 vwe

($1,145.00 CAN.-$1,1 9 9.00 U.S., F.O.B. Buffalo)

DQ-1 RHL ELECTRONIC DIGITAL GENERATOR

Model DQ-1, now being used by broadcast centresin Canada and the U.S. is the answer to Video -Audio Cueing Signals. It provides a signal similarto the Academy Leader used in the film industry.

+8DBM n

-12 DBM I

The video cueing signal-electronically gener-ated numerals, from 10 to 2, occur at 1 secondintervals. The audio signal consists of a 400 -cycletone at +8 dBm of 1/5 second duration, coin-cident with the numeral changes. (CSA andSMPTE Standards). Completely self contained

Years of technical experience in tele-vision broadcasting stand back of themany new advances developed byRichmond Hill Laboratories. Designed,engineered and manufactured inCanada, and used by broadcasters onall six continents, the wide range of RH Lsolid state equipment includes: StudioSwitching Equipment SynchronizingPulse Gen Video Test Signal Gen

1

Both thevideoand audio information are suppliedsuperimposed on the program channels withFail -Safe protection.

n HTONE SIGNAL(400 CPS)

FIG. 21/5 SEC.VISUALDURATION

in 1.75" x 19" of rack space, the DQ-1 requires onlythe loop thru program video, eliminating theneed for additional cameras and equipment toinsert the cueing signals. With the DQ leader,quick accurate video tape cueing can be accom-plished for playback.

Special Effects Gen Colour Bar Gen VideoDA Pulse DA Clamping Amplifiers DigitalCue Gen Digit Gen Clock System DriverRouting Switching Equipment (Audio Video)

All RHL products carry a 5 -year warranty, backedby skilled craftsmanship, quality componentsand rigid control ... important factors in build-ing a fine record of service to the televisionbroadcast industry.

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52 Circle Item 19 on Tech Data Card BROADCAST ENGINEERING

October 1967

We interrupt this magazine to bring you...

Late Bulletin from Washington

by Howard T. Head

Review of Communications Policy Under Way

President Johnson, in a special message to Congress, has called for a

comprehensive review of the country's national telecommunications policies.

A special task force of high officials has been set up to report to the

President within 12 months.

The emphasis in the President's message is on the expansion of world-wide

communications through the use of space satellites. The message points

out the need for a choice between general-purpose satellites, to serve

all communications needs, and special-purpose satellites, such as those

proposed for domestic television relaying by the American Broadcasting

Company, the Ford Foundation, and others (November 1965 Bulletin).

Although the emphasis in the message is on space communications, the task

force has also been directed to review the usage of the entire spectrum

as a whole. This review, together with the continuing rapid expansionof CATV and the growing land -mobile demands on the spectrum, is certain

to have a significant impact on television broadcasting of the future.

New Painting and Lighting Requirements

The Commission has amended Part 17 of its Rules governing the painting

and lighting of towers so as to bring these requirements into conformity

with similar FAA regulations governing nonradio structures. The principal

changes involve towers of 1500 feet above ground or higher. One little -

noticed change, however, would exempt many structures under 200 feet in

height from any painting and lighting requirements. No existing painting

and lighting may be abandoned, however, without prior FCC approval.

Existing towers not conforming with the new requirements must be brought

into compliance with them no later than September 5, 1970.

Relaxation of Transmitter -Visibility Rules Sought

The National Association of Broadcasters (NAB) is preparing to file a

petition requesting a relaxation of the Rule which requires that trans-

mitters not operated by remote control be visible from the operator's

position. Many stations, particularly those employing combined studios

and transmitters, have found compliance with this Rule quite difficult,

and have resorted to a variety of mirrors, holes -in -walls, and even closed-

circuit television cameras to provide the required visibility. The newNAB proposal would require only that the transmitting equipment and theoperator be on the same premises.

Installations not now meeting the visibility requirement must, in orderto comply fully with the Rules, be operated by remote control. This isa particularly burdensome requirement in the case of AM stations employingdirectional antennas; these stations must submit a skeleton proof of per-formance in support of a remote -control application, and repeat the proofof performance annually.

Many Stations Request Presunrise Authorization

The Commission is being deluged with requests for Presunrise ServiceAuthority (PSA) under the provisions of new Rules (August 1967 Bulletin).AM stations may request PSA's which permit presunrise operation as earlyas 6:00 a.m. with a power up to 500 watts, employing the staticn's day-time facilities. The use of auxiliary transmitters, which are not re-quired to meet performance standards, is permitted when operation isundertaken under a PSA. Fulltime stations may also take advantage ofthe new Rules, and a surprising number are doing so -- the advantage beingthat nondirectional operation requires neither a first-class cperator onduty nor a daily antenna inspection at the transmitter.

A substantial number of stations are requesting the Commiss:on tc reconsiderthe new Rules. Daytime -only stations feel that they could have been givenmore power and an earlier sign -on, while fulltime stations are objectingto the interference which will be received from the daytimers.

Short Circuits

The Commission has prodded the leading television -receiver manufacturersto improve the ease of tuning of UHF receivers. . .The Commission hasordered several VHF television translators in Cumberland, Maryland, toshift to UHF to protect local VHF reception and CATV distribution. . .Thetests to determine the feasibility of land-mobile/television channelsharing in the Washington, D.C. area (May 1967 Bulletin) are indicatingfar less interference to television reception than had been expected. . .

Several educational television stations have received permission to transmitmusic with slides during classroom -program breaks. . .The Commission tolonger recognizes the 50 uv/m contour as the limit for rural service forFM stations. . .The Commission has rejected an application fror a clear-channel station for regular operation with 750 -kw power -- several experi-mental applications for higher power are still pending (October 1966Bulletin).

Howard T. Head. . . in Washirgton

Why is Beldenspecified by mostbroadcast engineers?Belden designs and manufactures a complete line of audio, camera,and control cables to meet every TV and radio broadcasting, record-ing studio, and remote control need.Many Belden Audio and Broadcast Cables feature Beldfoil* shield-ing. This superior cable shield provides 100% protection againstcrosstalk ... increases electrical reliability ... reduces cable diam-eter and weight ... is easier to terminate ... usually lower in cost.Here is just a part of this complete line, available from stock. Askyour Belden Electronics Distributor for complete information. Re-quest also a copy of the latest Belden Electronics Catalog.

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October, 1967 Circle Item 20 on Tech Data Card 55

TELEMET'S"KEY"

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CCKEY IN I/Can be used with all cameras plus 4 -PLUM BICONS. Internal power

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TELEMET COMPANY185 DIXON AVENUE / AMITYVILLE, NEW YORK 11701 / PHONE: (516) 541-3600


WE GIVE IN!For a long time, customers have been asking us whywe're not in the video switcher business. Well, wefinally gave in. Telemet will now produce completevideo switching systems to your specifications. Up tothis time, Telemet has been supplying key compo-nents to other switching systems manufacturers. Ourspecial effects generators, for example, are in use byvirtually every switcher manufacturer. Because ofour intimacy with various switcher systems over theyears, we've been able to determine and select thebest approach for superior customized systems.

To help you with your switching needs, Richard T.Swan has joined us as Chief Applications Engineerfor this activity. Dick Swan is a nationally knownauthority having many years experience with alltypes of switching systems.

If you want assistance with your switching require-ments, please feel free to call on Dick ...and Telemet.

TELEMET COMPANY185 DIXON AVENUE / AMITYVILLE, NEW YORK 11701 / PHONE: (516) 541-3600

October, .1967 Circle Item 21 on Tech Data Card 57

NEWS OF THE INDUSTRY

INTERNATIONAL

New TV Outletfor Mexico City

A new commercial television chan-nel in Mexico City has been grantedto Corporacion Mexicano de Radio y

Television (Mexican Radio and Tele-vision Corp.). To be the fourth outletfor the city, the station will operateon channel 13.

Program production will beginwhen new studios are completed in

Multiple Cartridge Playback Units

'1100011, 011$1111011-000000 fiTen Spot Model 610B Five Spot Model 60513

... bringing a new dimension topushbutton broadcastingSpotmaster Ten Spot (holding 10 cartridges) and Five Spot (holdingfive) will reproduce any NAB Type A or B cartridge instantly at the pushof a button ... at random or in sequence. They may be operated manuallyor incorporated into programmed automation systems, using one, two orthree NAB standard electronic cueing tones.

The Ten Spot is designed for 19" rack mounting while the Five Spotis available either in an attractive walnut -finished case or with a 19" frontpanel containing a cartridge storage cubicle. Both are backed by Spot -master's iron -clad full -year guarantee.

For further information about these and other Spotmaster cartridge tapeunits, call or write today. Remember, Broadcast Electronics is the No. 1designer/producer of broadcast quality cartridge tapeequipment ... worldwide! =BROADCAST ELECTRONICS, INC.8810 Brookville Road, Silver Spring, Maryland 20910; Area Code 301, 588-4983

the early part of next year. and broad-casting operations are expected tobegin in the latter part of 1968.

NATIONAL

Southern California Sales Office

Andrew California Corp. has en-larged and relocated its SouthernCalifornia sales office. The office is

located at 615 N. Euclid Avenue andwill he supervised by Mr. DonaldCrumm, newly appointed DistrictManager.

Engineering and manufacturing op-erations will continue at their presentlocation in Claremont, California. In-quiries concerning antenna and trans-mission line products should bedirected to the new sales office.

Washington, D.C. Office

The Washington, D. C. office ofCollins Radio Co. has been moved toa new location in the Washingtonarea. The new location is RosslynPlaza, 1611 North Kent Street, Ar-lington, Virginia.

Main Office MoveWebster Engineering Co. has moved

its main office to new and largerfacilities at 1136 Gail Lane, SleepyHollow, Dundee, Ill. Partial stockingof some lines of broadcast equipmentwill make fast delivery possible inemergency cases.

Pilot Satellite Program Proposed

The Communications Satellite Corp.has filed with the FCC a proposedpilot satellite program to provide alltypes of domestic communicationsservices, including commercial andeducational TV.

As envisioned, the program willconsist of two satellites (at 97° and103° W. longitude) and 34 earth sta-tions of various capabilities (mostlyreceiving stations in the Mountainand Pacific time zones). An illustrativedistribution of service consisted ofone ETV and three commercial colortelevision signals to each of two timezones, 3600 trunk voice channels be-tween Los Angeles and New York,


FIRST BY ANY STANDARD

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The VIDEOGRAPH® Display Control Unitmodel 990A new pacesetter that meets today's challenge for instantaneous,economical TV broadcasting of News . . . Titles . . . Election Reports . . .

Sport Scores . . Weather Bulletins . . . and a myriad of other messagesrequiring no additional Camera Chains or artwork preparation!

The A. B. Dick Videograph:R; Model 990 Display Control Unit is unique in itslow-cost sophistication. It offers digital -to -video character conversion from64 different alphanumeric or special symbols, directly and instantly onto theTV screen-unerringly. Input to the unit can be from any 8 -bit data inputsource such as a keyboard. punched paper tape, magnetic tape, or Dataphoneline input. And, the VideographR, can store and display one completeframe of pre -selected information.

Its video output is compatible with standard TV signals, and informationmay be erased and corrected electronically. "Error -free" informationcomposed in the Videograph R may be fed as data output to be stored forfuture use in a punched paper tape or magnetic tape device.

The A. B. Dick Videograph R is ideally designed for the standard TV system,producing single or multiple line display in crisp, easily legible characters.It can even achieve vertical or horizontal crawl effects, and slow -rate"blinking" of words is also possible. For the complete story, contact yourarea Visual Electronics representative-or write for brochure.

VISUAL ELECTRONICS CORPORATION356 west 40th street new york, n.y. 10018 (212) 736-5840

Registered Trade Mark of A 3. C,::k Co

October, 1967 59

and 800 multipoint channels linkingNew York, Los Angeles, the North-west, and the Southeast.

News Transmission NetworkThe first phase of a new nationwide

news transmission network, engi-neered, furnished, and installed byLenkurt Electric Co., Inc., a sub-sidiary of General Telephone & Elec-tronics Corp., was cut into service onJune 27 by the Associated Press inLos Angeles. The first phase, whichcost some $850,000, connects APBureaus in the cities of Los Angeles,

San Francisco, Portland, Seattle, Spo-kane, Salt Lake City, Phoenix, Albu-querque, Dallas, Oklahoma City,Denver, and Kansas City. At a laterdate, the "backbone" transmissionsystem will interconnect AP Bureausin 12 midwestern, 10 southeastern,and three northeastern cities.

The data system operates at 75words per minute and has 22 Teletypeor teletypesetter circuits within thebandwidth of one standard telephonecircuit. AP officials said the new na-tion-wide network, when completedlate next year, will serve more than

CHECKthese

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our

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0

The all transistorized A-15 audio console has increased mixing

The AC -155 will now accommodate six low level audio sources,including the right and left turntables, and eight high-level

to help you expand your remote and studio production potential.

14 AUDIO INPUTS

sources.

NEW LEG DESIGN

rests are molded at outward angles to provide a solid jar -prooffoundation. Leg units are removable for easy transporting.

ADDED FLEXIBILITYPerfect as a full broadcast facility for production or recordingstudio, main studio control or any remote assignment. Solidstate console is removable. Additional features include 3 speedcustom turntable, lift -leaf work surface and all channel monitor /cue system.

Leg supports are of sturdy two inch chrome tubular steel. Foot

Also Avail. in Stereo.AC -155 AUDIO CONTROL & REMOT UNIT $1095.

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4200 newspaper and broadcast -stationmembers in the U. S.

ORGANIZATIONS

Central CanadaBroadcasters' Association

The Central Canada Broadcasters'Association will hold its annual con-vention on October 22, 23, and 24 atThe Inn on the Park, Toronto. Thiswill be a joint engineering/manage-ment function, with separate pro-grams for the two groups.

George W. Bartlett, NAB vice-president for engineering, will addressthe engineering luncheon on October24. Technical papers to be presentedat the convention include: "CircularPolarization of FM and TV Anten-nas," "A New System of Intrical PulseDistribution for TV," "Technical Re-quirements in Education Television,"and "Technical Advances in Com-munications."

Equipment exhibits will occupy thewest wing of the Inn on the Park.

Something to buy or sell?Use the Classified.

TV LINE EQUALIZERTYPE AV -535

The AV -535 Equalizer com-pensates for losses in RG-11/U (75 ohm) cable and itsequivalents. It is capable ofequalizing 50 to 300 ft. in50 ft. increments. Terminalsare arranged to provide forsimplifed strapping of differ-ent cable lengths. Units arefoamed and hermeticallysealed in steel cans.Impedance: 75 ohms ±-2 ohms to 8 megs.Attenuation of Cable plus Equalizer: 3 db.Size: 2 x 31/2 x 5" (excl. mounting stud length).

PULSE & VIDEO DELAY LINETYPE AV -397

These units are used withany 75 ohm system foreither pulse or video delay.Although intended primarilyfor equalizing the delays invarious lengths of coaxialcable, the line can be usedwherever an appropriate de-lay is needed. Each AV -397consists of 7 individual de-

lay lines, each having its own input & outputterminals. By connecting the output of 1 tothe input of another, 83 different time delaysare available in .025 ,u,s steps from 0.25 Asto 2.075 As. The total time delay is the sum ofthe delays of the individual lines that areconnected.

WRITE FOR CATALOGPRIME SUPPLIER TO TV INDUSTRY

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255 E. 2nd ST., MINEOLA, N.Y. 11501




When engineers get together,the conversation turns to pickups.

PHOTOGRAPHED BY FRANZ EPSON AT THE CAPITOL TOWER, HOLLYWOOD.

It's an irresistible topic.Especially since Stanton came out with the Model 500 stereo cartridge.That's an engineer's pickup, if there ever was one.Beautiful curve-within 1 db from 20 to 10,000 Hz, 2 db from 10,000 to 20,000 Hz.Fantastically small moving system to trace the wildest twists in the groove.Light weight (only 5 grams!) to take advantage of low -mass tone arms.And, of course, Stanton's legendary quality control.No wonder engineers use the Stanton 500 for critical broadcastingand auditioning applications.And to impress other engineers with their pickupmanship.(Available with 0.7 or 0.5 -mil diamond, $30; with elliptical diamond, $35.For free literature, write to Stanton Magnetics, Inc., Plainview, L.I., N.Y.)

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Ultrasonic energy is the most effective and economical way to thoroughly andrapidly clean motion picture film without mechanical scrubbing and wiping. Thecold bailing effect (cavitation) of ultrasonic energy performs the entire opera-tion, Oily the solvent touches the film and a forced air, flash dry -off removes allsolvent and residue.

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Telephone: 312-338.30405427

Daytime BroadcastersAssociation

A meeting of the Daytime Broad-casters Assn. was held in Chicago'sSherman Hotel on August 10 and 11to discuss the effects of the new FCCpresunrise rules. In clinic sessions,both legal and technical aspects weretreated.

An introductory speech was deliv-ered by Ray Livesay, chairman ofthe association's board of directors, inwhich the history of the DBA's ef-forts with regard to presunrise opera-tion were traced. The speakerobserved that while some stations willgain from the new rules, others willlose hours of operation.

In other talks, legal effects werediscussed by Ben Cottone, Washingtoncounsel for the DBA; the technicalconsequences were dealt with byEverett Dillard, a Washington con-sulting engineer; and the FCC's pointof view was presented by Wallace E.Johnson, assistant chief of the FCCBroadcast Bureau.

IEEE

The Broadcasting Group of theInstitute of Electrical and ElectronicsEngineers will hold its Western Con-ference on Broadcasting November 9and 10, 1967 at the Ambassador Hotelin Los Angeles. The purpose of theconference is to offer broadcasters anopportunity to "gain first-hand knowl-edge of solutions found and proposedfor current and future problems."

Approximately 300 engineers, man-agers. and university students are ex-pected to attend the meetings. Theywill hear papers presented on inter-ference -producing ground coupling,laser communications, satellite broad-casting, antenna design, color TV, andCATV.

NAB

Members of the NAB's 1968 Broad-cast Engineering Conference Commit-tee have been announced.

Appointed chairman is Albert H.Chismark, director of engineering forthe Meredith Broadcasting Co., Syra-cuse, N.Y.

Other Committee members are Le-Roy Bellwood, chief engineer, KOGO-TV, San Diego; William S. Duttera,director, allocations engineering,NBC. New York; George Jacobs, en-gineering director, Corinthian Broad-casting Corp., New York; Leslie S.Learned, vice-president for engineer-ing, MBS, New York; Clure H. Owen,manaeer of allocations, ABC, New



Multiple choice-every onea right answer!Bauer's line ofaudio consolesThere's a compact Bauer console that'sright for any audio operation, simple orcomplex. Each console is self-containedand highly versatile, for speed and ac-curacy in cueing, monitoring, mixing andprogramming. Each is of typical Bauerhigh quality and reasonably priced.Model 915 - for the remote TV truck;8 -microphone versatility with multiple in-puts for turntables, tape units, projectors.Model 912S - for 5 -channel stereo instudio production and control rooms.Handles tape prerecording, remote inter-views, panel shows, commercial ETs, IDspots, etc. As on -the -air console, givesfast, precise control over 13 inputs.Model 912- a 5 -mixer model for produc-tion preprogramming in studio or on re-mote location; excellent primary, on -the -air unit for smaller stations.Model 910S -8 -mixer stereo console withall the inputs and controls needed by anystation, AM or FM, large or small.Model 910D - dual unit, easily handlestwo programs simultaneously; 8 mixingchannels and more useful features thanmost consoles twice its size.

Let a Bauer add new dimensions to youraudio capabilities: modern, high-speedcontrol, versatility, simplicity, and con-venience. Write to us for full technical in-formation.BauerELECTRONICS CORPORATION1601 California Ave.Palo Alto, California 94304

GrangerAssociates

COMPANY


October, 1967

York; James D. Parker, director,transmission engineering, CBS Tele-vision Network, New York; Robert J.Sinnett, vice-president for engineering,WHBF, Rock Island, Ill.; John T.

Wilner, vice-president in charge ofengineering, The Hearst Corp.. Balti-more; and Benjamin Wolfe, vice-president for engineering, Group W.New York.

SMPTE

The Society of Motion Picture andTelevision Engineers has announcedthe recipients of several of the society'sannual awards. The SMPTE JournalAward was given to Walter C. Sny-der, of the Eastman Kodak Co., forhis 1966 paper, "An investigation ofAgitation in a Continuous ImmersionFilm Process."

The 1967 Herbert T. Kalmus GoldMedal Award went to John M. Waner,also of Eastman Kodak. Recipients ofthe award arc honored for their con-tributions to the development of colorfilms, processes, techniques, or equip-ment.

Other awards were: Eastman KodakGold Medal Award to Samuel L.

Postlethwait (Purdue University):1967 Progress Medal Award to Gor-

withGreenlee

punchesHere's the simple speedy way to cut smooth,accurate holes in metal, hard rubber, plas-tics, epoxy, etc.Save hours of hard work . . . punch clean, trueholes in seconds for sockets, controls, meters,and other components. Easy to operate. Simplyinsert punch in a small drilled hole and turn witha wrench. For use in up to 16 -gauge metal. Avail-able at leading radio and electronic parts dealers.

GREENLEE TOOL CODIVISION OF GREENLEE BROS. CO

1866 Columbia Avenue, Rockford, III. 61101


measureIWA1 MODULATION

MI PERCENTAGE

PEAK

DEVIATION

FROM 3 MHz to 1000 MHz

AFM1 Modulation MeterCombines Precision Cepebilities

Do you require complete modulationmeasurements - either AM or FM -quickly - easily? Check the AFM1. Thisproven design provides simplicity of op-eration, broad coverage and high accur-acy. Ideal for measurement of AM andFM from signal generators, transmitters,mobile equipment - or as a stationmonitor.

FEATURES:

Wide Frequency range: 3 MHz to320 MHz on fundamentals, to over1000 MHz with harmonics.

Accuracy: 3% on both AM and FM.

Four AM Modulation ranges: 3(4 to100% full scale.

Five FM Deviation ranges: ±3 to300 kHz.

Measurement of positive and nega-tive modulation and deviationpeaks.

Low Residual distortion: Less than0.5%.

The advantages of both AM and FMMeasurements coupled with simplicity ofoperation have made the AMF1 one ofthe most -used combination modulationmeters in the world today.Like more details? Send for brochuretoday!

THE LONDON COMPANY811 SHARON DRIVE WESTLAKE. OHIO 44145RADIOMETER rgel

COPENHAGEN WP4iIn Canada Bach Simpson Ltd . Bon 2484. London. Ontario

Circle Item 29 on Tcch Data Card63

SEE OUR EXHIBIT AT THE NAEB SHOW /BOOTH 125 / DENVER / NOV. 5.8

All Digital ColorSync Generator

Exclusive Features - 411 pulses and transitions clock derived No monostables - no delay lines ntegrated circuit reliability Dual outputs - permit pulse assignment with

full standby Subcarrier vs. horizontal jitter better than

D.25 nsec. Pulse jitter better than 4 nsec throughout frame 13/4" rack space - including all "Add -In"

modules

Add -In Modules - Monochrome Genlock Bar Dot Generator Color Genlock Sync Changeover Switch

MonochromeModel TSG-2000M

$1,000ColorModel TSG-2000C

$1,500

NEW AORTA -SYNC'"IdenticalPerformanceat a GreatSavings!

Ideal for . . . REMOTE FIELD APPLICATIONS . .

PORTABLE TEST GENERATOR ... SYSTEM SPARE.. FULL TIME DUTY. Economical, yet absolutelyno sacrifice of waveform performance.Specifications are the same as ModelsTSG-2000M/C, but Add -In modules are notavailable because of ultra -compact dimensions of31/2" h x 5,/4" w x 10" d.

MonochromeModel TSG-1000M

$695ColorModel TSG-1000C

$1000

.... from TeleMation - where experience powers pacesetting products!

TELEMATION, INC.2275 So. West Temple / Salt Lake City, Utah 84115Telephone (801) 486 7564

don A. Chambers (Eastman Kodak);SMPTE Scholarship Fund Award toL. David Pratt (Rochester Institute ofTechnology); and honorary member-ship to Dr. John G. Frayne (promi-nent audio scientist and technicalauthor).

TRANSACTIONS

In a series of transactions, RikerVideo Industries, Inc. has acquiredseveral electronics manufacturingfirms. The first was Continuous Pro-gress Education, Inc., which designs,manufactures, and installs audio -videocommunications systems for schools.Next came the purchase of ITV, Inc.,designer and installer of CCTV equip-ment. Most recently acquired wereRichmond Hill Laboratories, Ltd. andLeitch Research and Development,Ltd., both of Toronto. Richmond HillLaboratories, manufacturing arm ofthe Canadian complex, producestransistorized broadcast items whichwill complement Riker's regular line.

Visual Electronics Corp. has ac-quired the assets of KRS Instruments,a division of Datapulse Inc. The newlyacquired facility manufactures car-tridge tape recording and playbackequipment for application in the pro-fessional broadcasting and data -instru-mentation fields.

PERSONALITIES

Mr. Heinz Blum has been promotedto the position of senior vice-presidentin charge of advanced engineering ofEntron, Inc. He will be responsible forthe implementation of new researchand development programs for prod-ucts to be manufactured in two to fiveyears.

Elton B. Chick has been appointedgeneral manager of WCIN, Cincinnati,one of the Rounsaville Radio Stations.For the past 21/2 years, Mr. Chick, a20 -year Rounsaville employee, hasbeen general manager of WLOU,Louisville. Previously, he held an ex-ecutive engineering position for all theRounsaville stations. Mr. Chick re-places Donald K. Clark, who wastransferred to the Rounsaville facilityin Tampa, as general manager ofRadio Station WDAE.

Anaconda Astrodata Co. has ap-pointed Bruce Walters to the newlycreated position of director of manu-facturing. Mr. Walters will be re-sponsible for all facets of manufactur-ing operations at the Anaheim plant.



Two appointments have been an-nounced by Philips Broadcast Equip-ment Corp. Rupert F. Goodspeed willbe product manager, broadcast equip-ment; and Abe Jacobowitz will besales manager of television broadcastequipment. Mr. Goodspeed came toPhilips from RCA, and Mr. Jacobo-witz was formerly with Communica-tions Industries Corp.

OBITUARIESMr. Charles J. Starner, 59, manager

of VHF television transmitter engi-neering for the RCA Broadcast andCommunications Products Division,died July 15 at his home in McMur-ray, Pennsylvania.

An RCA employee since 1940, Mr.Starner was known in the broadcastindustry for his design work in themedium- and short-wave transmitterfield. He graduated from GettysburgCollege with a BSEE degree and wasa member of the Institute of Electricaland Electronics Engineers.

Mr. Joe Davis, long-time KXLYtelevision studio supervisor and designengineer, died recently. He was 55years old and had been with KXLYRadio, and later Television, for 21years.

Hugo Gernsback, pioneer in elec-tronic invention, author, and publisherdied on Saturday, August 18, in NewYork City. He was 83 years old.

In 1925, Mr. Gernsback foundedradio station WRNY, and three yearslater, with the help of Pilot RadioCorp. engineers, started televisionbroadcasts. Postage -stamp -size imageswere received on crude scannersowned by 2000 amateurs in the NewYork area.

During his long publishing career,Mr. Gernsback put out more than 50magazines, including the first radiomagazine, Modern Electrics in 1908,and the first science -fiction publica-tion, Amazing Stories in 1927. He iswidely credited with having writtenthe first true science -fiction story, andwith coining the term itself.

His awards and associations in-clude: Marconi Memorial WirelessPioneer Medal, Veteran Wireless Op-erators, 1950; Gold Medal of Luxem-bourg, Grand Order of Oaken Crown;Silver Jubilee Trophy, Belgian SocietyHelios, 1953. Member American Phys-ics Society, AAAS; founder WirelessAssociation of America.

At his death, Mr. Gernsback held80 scientific patents. He was editor -in -chief of Radio -Electronics andother publications. A

0 SEE OUR EXHIBIT AT THE NAEB SHOW /BOOTH 125 / DENVER / NOV 5 8

Optical MultiplexerFor broadcast and ETV studiosThe Model TMM-203A is designed forselective projection of two 16mmfilm projectors and one 2" x 2"slide projector into a single televisioncamera. A rugged pedestal base withthe precisely machined, cast aluminumoptical transfer assembly assurespermanent optical alignment.

OPTICAL TRANSFER ASSEMBLY

First surface mirrors are operated byelectric motors for fast, yet gentle"w pe" switching. Mirror actioneliminates the need for separateprojector dousers.

Plus Features -

LAMP VOLTAGE CONTROLS providedfor projectors

LOCAL and REMOTE CONTROL provisions CUSTOM MOUNTING available for all

brands and types of cameras andslide projectors

For complete details, request Form TPB-50Model TMM-203A ONLY $1,295.00

Television Equipment for Education, Industry and Military .. .

MULTICASTER

VR 660 Video Processor

PORTA-SYNC

2:1 Interlace Sync Generator

TELECTERN

EIA Camera Control

.... from TeleMation - where experience powers pacesetting products!

OTELEMATION,INC.

2275 So. West Temple / Salt Lake City, Utah 84115Telephone (801) 486-7564

October, 1967


65

A PROMISE IS A PROMISE

Broadcasters in all parts of the country purchased Collins900C-1 Stereo Modulation Monitors before type -approvalrules and regulations for stereo monitors were establishedby the FCC.

Collins promised these customers that their 900C-1 unitswould be modified to meet any forthcoming type -approvalrequirements.

Rules and regulations concerning stereo monitors wereannounced by the FCC earlier this year, and Collins haswritten to all 900C-1 customers, reminding them of themodification to which they are entitled.

If your station has received one of these letters, don't delayreturning the modification request form.

We want you to have a type -approved monitor.

And we want to keep our record of always keeping ourpromises.

COMMUNICATION COMPUTATION: CONTROL

(A

COLLINS RADIO COMPANY / DALLAS, TEXAS CEDAR RAPIDS, IOWA NEWPORT BEACH, CALIFORNIA TORONTO, ONTARIOBangkok Frankfurt Hong Kong Kuala Lumpur Los Angeles London Melbourne Mexico City New York Paris Rome Washington Wellington



NEWPRODUCTS

to to miFor further information about any item, circlethe associated number on the Tech Data Card.

Light Fixture(51)

A lensless light fixture that ap-proaches the intensity range of a

standard 2K Fresnel unit has been in-Inc.

The Model LQF10-50 Super -Beam"1000" permits focusing from spot toflood with a ratio of 11 to I.

Using a 1000 -watt (3200°K) tung-sten -halogen quartz single -ended frost-ed lamp, the LQF10-50 operates di-rectly from 120 volts, AC or DC.without boosting, and produces 50 to560 footcandles at 20 feet from theflood to spot focus positions. The two -and four-leaf barndoors rotate 360°and fold flat.

Motion picture and television mod-els are available. The MP version(LQF10-50) weighs 1014 pounds andcan be stand mounted or supportedby standard grip equipment. Focusingis accomplished by rotating a plasticknob on the bottom of the housing.The TV version (LQF10-50/TV)weighs 11 pounds and is supplied witha yoke incorporating a C -clamp formounting. A steel loop (for pole op-eration) replaces the plastic knob forfocusing the TV model. Both units are

MOVING?Don't lose touch . .

RECEIVE BE AS USUAL(INCLUDE OLD AND NEW ADDRESS)

BROADCAST ENGINEERINGCIRCULATION DEPT.4300 W. 62nd St.,

Indianapolis, Ind. 46206

AMCI BROADCASTING ANTENNASFor ITV, UHF -TVVHF -TV and FM

Directional and OmnidirectionalTV Antennas

Directional and OmnidirectionalITV Antennas

Dual Polarized Directional andOmnidirectional FM Antennas

May be top or side mountedAMCI Antennas are ruggedly de-

signed and constructed of noncorro-sive materials such as 6061-T6 alu-minum, copper, and stainless steel.This type of construction, combinedwith an electrical design that re-quires few transmission line seals(from 1/8 to 1/4 as many as othercomparable antennas), yields an ex-tremely dependable antenna thatrequires essentially no maintenance.

AMCI also custom designs an-

tenna arrays to meet particular re-quirements. For a description ofone of AMCI's custom designs (AnFM Antenna on the Chrysler Build-ing), write for Bulletin 10.

ALFORDManufacturing Company

120 Cross Street, Winchester(Greater Boston), Mass. 01890Telephone: 617-729-8050 TWA: 710-348-1063

Coble Address: AMCIBOSFM

UHF

ITV VHFCircle Item 35 on Tech Data Card

Operating remote control?Be safe and sure with the

NEW! ALL ,,r2} RF

AMPLIFIER FROM WILKINSON!Features of the Model TRF 1A:

VERY LOW DISTORTION AND CARRIER SHIFT BROAD GAIN CHARACTERICTIC:S EXTREME STABILITY EXCEL_ENT SELECTIVITY ULTRA LINEARITY

PRICE: $ 395For complete details write:

1937 MacDADE BLVD.

JL `J_JWOODLYN, PA. 19094

ELECTRONICS, INC.PHONE (2151 874-5236 874-5237

October, 1967


67

Photo Researchintroduces aneasier, faster,more accurateway to test TVcameras .

The SPECTRA TV OPTOLINER*is a high resolution, precision TV cameratester that saves space by eliminating theelaborate test equipment formerly used forthis operation. Now being used by RCA intheir Burbank production facilities, theOptoliner attaches directly into the cameralens mount and provides microscopic align-ment (within 0.002") of the slide mountedtest patterns to the center of the cameralens. Ideal for use in production facilities,quality control operations or in standardslabs, the Optoliner contains a constant, ad-justable light source, and a special meterto indicate the exact illuminance and colortemperature falling on the face of thecamera tube. For more information on thissimplified approach to TV camera testing,write, wire or phone today!Trademark of Photo Research Corp.

Karl Freund.President

PHOTO RESEARCH corp."Photometric Equipment for Science and Industry"

837 N. Cahuenga Blvd., Hollywood, Calif. 90038Telephone: (213) 462-6673 Cable: SPECTRA

priced at $125, and the same group ofaccessories is available for the MPand TV versions.

A A..

TV Color Processor1521

The Model MTV -30 color processorhas been designed by Treise Engineer-ing, Inc. to meet television needs. Theself-contained unit occupies 17' X 9'of floor space. Stated warm-up timefrom ambient 70' to the required100-110° is 20 minutes; a "propor-tional control" system provides con-trolled amounts of heat to maintainproper temperature. All tanks areinsulated for minimum heat loss. andall solution pumps are "magnetic cou-pled" to avoid pump sealing problems.

The MTV -30 processor is designedto handle all types of Ektachromefilm. It operates up to 40 fpm. Allprimary chemicals are individuallycontrolled by proportional pneumaticsystems, and all film -transport cle-

SPOTMASTERThe all solid state AD1A

AUDIODISTRIBUTIONAMPLIFIER

to) 4 * *474 c cC

Meet the AD1A, a solid state audio dis-tribution amplifier specifically designed forAM, FM and TV broadcast stations andrecording studios. The AD1A distributesaudio signals via five separate outputchannels (up to 25 with the addition ofADIA-X extenders), and incorporates afront -panel VU meter and monitor jack topermit visual and aural monitoring of theincoming signal at the output of the lineamplifier. Response is essentially flat from40 to 20,000 Hz, with low distortion andnoise, 60 db channel isolation and 12 dbpeak factor. For further information, writeor call today:

BROADCAST ELECTRONICS. INC.8810 Brookville Road

Silver Spring, Maryland 20910Area Code 301 e 588-4983

AEMCOLOR BURST GENERATORS

ENABLE FADE, LAP OR WIPE

TO ANY COLOR HUE OR BLACK

The new, solid-state CBG-1 Color Burst Generatorlets you go to red, green or blue (or any other hue)by generating a black burst signal with a coloredbackground. The unit also lets you lap or wipe toany color as a transition, or use the signal as abackground for slides or movies. The CBG-1 pro-vides adjustable burst, sync, minimum blanking,luminance, chrominance and hue. It features full

360° input phase shift, two 75 -ohm outputs, com-plete front panel control and monitoring; andoccupies only 13/4" of rack space. A single knob on

a remote control panel lets you set the hue andreturn to black. The CBG-1 is only $595.00, andcan be factory -modified as a B & W video tintingfacility for only $25.00 extra. The Model BBG-1(black only) is $545.00.

VIDEO DISTRIBUTION

AMPLIFIERS FEED TO

SIX ISOLATED OUTPUTS

AEM Video Distribution Amplifiers are designed tobe INSTALLED and FORGOTTEN. Constructed ofall solid-state silicon components, they providedistribution to six isolated outputs, and offer

excellent performance over a temperature rangefrom +32°F to +130°F. The amplifiers exceed all

NTSC color and monochrome specifications, pro-vide front panel input and output test jacks for each

line, and have their own regulated AC to DC power

supply. Provided in rack -mount (DAR) or portable(DAP) configurations, a "Sync Add" option is

available for either. The rack -mount series alsoincludes a remote gain version which helps solveperplexing cable routing problems. Rack -mountprices are: DAR -1 Standard, $340.00; DAR -2 Sync

Add, $365.00; DAR -3 Remote Gain, $395.00. Port-able series prices: DAP -1 Standard, $350.00;

DAP -2 Sync Add, $375.00. Rack -mount models are

11/4" high. Portable units are 51/2" wide, 5" highand 8" deep.

For complete information and specifications, ca IIor write:

APPLIED ELECTRO MECHANICS,INC.2350 Duke StreetAlexandria, Virginia 22314PHONE: (703) 548-2166




ments are completely removable fromthe processor for maintenance andinspection. Replenishers are meteredby means of gravity -fed flowmeters.Drying is achieved by a system thatcombines conventional and impinge-ment methods.

Crab Pedestal1531

The new Gibraltar crab pedestal isfor use with broadcast TV camerasand similar large instruments weigh-ing up to 200 pounds. This Quick -Set,Inc. pedestal provides crab or tricycle

YOU CAN GET MOREFROM YOUR CARTRIDGES

4.-41/

JOA gives you MORECARTRIDGE PERFORMANCE

... that's practical!MORE ENGINEERING TIME

... that's economical!Let JOA Cartridge Specialists reconditionand rebuild your worn cartridges and keepyour engineering personnel "engineering."-JOA will inspect, service and re-

load your cartridges with ANYLENGTH tape

NO MINIMUMNO EXTRA CHARGE FOR-

(a) FOAM TEFLON -FACED PRES-

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ALL cartridges PRETESTED under ac-tual broadcast conditions

48 -hour Processing

Need NEW CARTRIDGES fast? JOA willship immediately . . . from stock .. .

any size Fidelipac, precision manu-factured NAB cartridge.

JOA-the cartridge service of author-ity-.serving the broadcast industry.

phone or write

A"Jo A

Cartridge ServiceP. 0. Box 3087Philadelphia, Pa. 19150Area Code 215, TUrner 6-7993

steering selected by shifting a lever. well as other sizes and types of wheelsA steering column is mounted on the on special order.end of the right rear arm and carriesa I2 -inch steering wheel which con-trols the direction of movement.

The central pedestal contains anelevator mechanism which provides20 inches of height adjustment byturning the hand wheel. The pedestalaccommodates all standard Gibraltarheads and, with available adapters,other makes of heads.

The standard pedestal is providedwith 8" X 11/2 " wheels equipped withbrakes and cable guards: 10" x 31/2 "pneumatic wheels are available, as

* *

Tape Delay Recorder154)

Delay continuously variable from

"Fasttaitie, Pqtroitotaitee,I"says DICK CHARLES ...

01w

MODEL LRP

"Our equipment is used continuallyand low maintenance and reliabilityare important criteria. When wechanged to solid state Lang Elec-tronics equipment not only did wereduce our maintenance costs andloss of production time but theaudible difference in performancewas fantastic."

DICK CHARLES,Dick Charles Recording

CHECK THESE ADVANCED FEATURES: ALL SOLID STATE COMPATIBLE WITH EXISTING HEADS LOW NOISE HIGH RELIABILITY FRONT PANEL SWITCH-ING OF MIC. AND LINE RECORD ALIGNMENT CONTROLSON FRONT PANEL PLUG-IN CONSTRUCTION OPTIONALMICROPHONE PREAMPLIFIER HIGH OUTPUT RECORDELECTRONICS LOW DISTORTION LINE AMPLIFIER SAFE/RECORD SWITCH MONITOR JACKS COMPACT SIZE.

FREQUENCY RESPONSE: -Z2 db 30-18 KHZ at 15 ips± 2 db 50-15 KHZ at 71/2 ips± 2 db 50-7.5 KHZ at 33/4 ips

For complete details and new 1967 Lang Electronics catalog write today to:

LANGELECTRONICS, INC.507 FIFTH AVENUE NEW VORA N.V. 10017

For all your audio needs - LOOK TO LANG !


October, 1967


69

41.

ve. PI lase :allCa. rvino

DRAFTSMAN -

ion Equipmentp3 gtv,j,

for -'1 on TrUnSiTtiSSoRaFTSMANn 3ccidt n1

137-tielpPI, ETV, (ATV

D: ELECTRICI-ANS

ea*. 'SAE, c_lease Rugged, reliable type to ELEvraotocsenc.

anford., Calif.

experienced.To _.

r, pls.intact help With top-quality color sumerelectronic ,..--

nce. UrgEn. andblack-& white TV trans- plan, vacation. perm2nd classlicense n

cell Dnice, , .

Electronics.935-7 "3.

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VAC1J-BLAST,593-7658. "e`r.s"'t .

N, DESIGNERSech. Serv. 744

ENG1

563.c,,,

So far, there's only one applicantIt's Lenkurt's 76 TV microwave transmission system.

This is the system that's bringing top-quality color andblack & white TV into areas where they used to think some-thing was wrong with their picture if it didn't have snowmost of the time.

For instance, take the 76 TV Studio Transmitter installationat station KOLO-TV in Reno, Nevada. Since the 76 istransistorized, the new system operates with practically nomaintenance, quite a bonus to KOLO-TV because one oftheir microwave terminals is located on Freel Peak, where20 foot snows and 100-200 mile winds are not uncommon.

Another outstanding feature of the 76 system is its versa-tility. At the University of Kansas Medical Center, a 76 ETVsystem makes it possible for students to participate in classesbeing presented at a sister campus, 45 miles away. This is oneof the few two-way ETV systems in existence. This system issignificant because of the high resolution it provides forremote observation of medical techniques.

And the Columbia Basin Microwave Company is using ourmicrowave to transmit two off -the -air pickups through anextensive 76 network to serve several CATV companies andschool districts.

So, whether you're plannmg a community TV setup, anEducational TV program, or want to join a network, and youwant rugged, reliable equipment to help with top-quality colorand black & white TV transmission, you'd be doing a smartthing to write us for the resume on our money -saving, solid-state 76 TV microwave system.

Lenkurt Electric Co., Inc.. San Carlos, Calif. Other officesin Atlanta, Chicago, Dallas, and New York City.

LEA/111/RT ELECTRICSUBSIDIARY OF

GENERALTELEPHONE & ELECTRONICS GT&E



25 to 375 msec at 30 ips is providedby the Audio Instrument Co. Model303 time -delay recorder. The unit isequipped to provide multiple -headoperation, and as many as 15 play-back heads can be accommodated.

Mobile Lab Cart(551

A four -deck mobile instrument cart,the CE -1500-6, is available from

3 NEW HEADS INYOUR AMPEX

FOR LESS THAN $100.00

Our heads are manufactured undercontrolled laboratory conditions andare guaranteed to meet or betteroriginal equipment specifications. Allproducts must pass exacting qualitycontrol tests on Ampex equipment atour plant. We will put three new fulltrack or half track heads in yourAmpex assembly for $97.50. We willdeliver your assembly back to you byreturn mail. We have loaner assem-blies for your use if you need them.We will put four new heads in yourAmpex VTR audio assembly for$310.00. Send for Brochure.

TABERManufacturing and Engineering Co.2619 Lincoln Ave., Alameda, Calif.

94105

Cambridge Electronics, Inc. Mountedon 4 -inch swivel casters, the cartprovides 1800 square inches of space,with outlets and live cord available.

The cart is made of 1 -inch stainlesssteel with solid deck platforms weldedto the legs. Each laminated deck restson 38 -inch steel rods spaced 312inches apart. If desired, the deck canbe removed to let the instrumentsrest on the grille to allow for heatcirculation.

Overall dimensions of the unit are5858" x 240'8" x 311/4", with thetop deck 55" from the floor. Decksare 21" X 29" and are spaced, from

the bottom up, 13, 14, and 171/4

inches.

Helical -Scan Video Tape(56)

A family of video tapes designedspecifically for helical -scan recordershas been placed in production byMemorex Corp. The 79 series ofvideo tapes features a new binderformulation designed to provide extradurability, fewer dropouts. and longerstill -frame life. The tape is also in-tended to provide higher S'N ratioand low abrasive characteristics forlonger head life. The tapes are avail -

Why are we

me wager in

tower construction?

We keep on top

of me lob.

Right from the bottom up. You see, there'smore to putting up a tower than ordering thesteel and connecting the pieces. We startwith the soil. Lab tests tell us the type offoundation needed to support the structure.Then we make sure we get a thoroughknowledge of weather conditions. Heat,

cold, wind, ice will affect the tower. Manydetails need checking. Reliable decisionscan come only from the judgement and skillof years of experience. We call it totalcapability. It gives our customers totalsecurity. If you're planning any kind of tower,call us. We'll get on top of it right away.

DRESSERCRANE, HOIST & TOWER DIVISION

FORMERLY DRESSER-/DECO CO. ONE OF THE DRESSER INDUSTRIES

877 MICHIGAN AVE., COLUMBUS, OHIO 43215Phone area 614 299-2123 TWX 810-482-1743

Branch: 2314 Redondo Beach Blvd., Gardena, Calif. 90247 TWX 910-346-6338


October, 1967


71

Model AA -200

SOLID STATE AUDIO AMPLIFIERFrequency Response:-±-1db, 20 to 20,000 cycles at 100MW±2db, 20 to 35,000 cycles at 100MWHarmonic Distortion:Less than 1%, 20 to 20,000 cycles at 100MWLess than 2%, 20 to 20,000 cycles at 200MWInput:50 to 150 ohms balanced (mu metal shielded,

permalloy core transformer)2,000 or 100,000 ohms unbalancedGain:70db, 50 ohm input, 8 ohm load65db, 2,000 ohm input, 8 ohm load

Output: 500 and 8 ohms(grain oriented transformer)

Circuit: 7 transistors, 1 thermistorControls: Locking volume controlConnections: Barrier stripPower Supply: 9 volts DC, 100 MA

(accessory power supply available -Round Hill Model PS -200)

Construction: Brown enameledsteel case

Size: 9"L x 23/4"W x 31/4"HWeight: 28 ounces

50 Including complete Technical Data and SchematicPrice: 34 Send check or money order-we pay postage.

ROUND HILL ASSOCIATES INC.A MILO ELECTRONICS SUBSIDIARY

434 Avenue of the Americas, New York, N.Y. 10011

Model PS -200

SOLID STATE POWER SUPPLYAn all -transistor general purpose power supply, the Round Hill Model PS -200is particularly suited for use in applications requiring a stable, well -filteredDC source. It employs Zener referenced voltage regulation, and delivers 9volts DC at loads up to 200 MA with complete dead short protection. A lock-ing screwdriver -adjusted programming potentiometer permits the outputvoltage to be adjusted over a one -volt range.

Input Voltage: 105-125 volts AC,60 cycles, 5 watts

Regulation: Line + load 5 MVRipple: Under full load 10 MV, peak to peakOutput Voltage: 9 volts DC

(adjustable over 1 volt)Maximum Load Current: 200 MA

Controls: Locking programmingcontrol

Connections: Barrier stripConstruction: Brown enameled

steel caseSize: 9"L x 23/.,"W x 31/4"HWeight: 44 ounces

Price:;2450 Including complete Technical Data and SchematicSend check or money order-we pay postage.

ROUND HILL ASSOCIATES INC.A MILO ELECTRONICS SUBSIDIARY

434 Avenue of the Americas, New York, N.Y. 10011

able for all helical -scan recordersin all standard configurations andlengths.

Transmitter Logger(571

The AL -400 is designed for theeconomy -minded station that desiresto possess continuous line chart log-ging. This Rust Corp. equipment dis-plays a full 24 -hour logging segmentwith front -panel parameter notation.The basic unit offers all the standardAutolog features, such as 62 days ofchart on a single roll, calibration witha pointer that is visible when adjust-ing, all solid-state circuitry, and front -panel adjustments. The completecharting system is mounted on a sin-gle 31/2 inch high standard 19 -inchpanel; it includes a self-containedpower supply.

The patented Rust continuous linecharting system samples and recordseach parameter every eight seconds.Twelve inches of chart paper equalstwenty-four hours of logging. Rubber-stamp scales customized to station re-quirements are included in the basicunit price.

Something to buy or sell?Use the BE Classified.

VIDEO RECORDING ENGINEER

CAREER

OPPORTUNITY

Large manufacturer needs allexperienced Video Tape Re-cording Engineer to work onnew product processing.

This career position re-quires a thorough knowledgeof video tape recording, edit-ing and handling proceduresplus a minimum of threeyears experience with broad-cast quadruplex recorders andhigh quality color TV pro-ductions. Applicants shouldalso be familiar with the op-eration and maintenance ofhighband color recorders.

The location offers pleasanttemperatures year 'round, 4 -season recreation and a finecommunity life.

Interested? Then write,stating your background to:Dept. #183 BROADCASTENGINEERING

An Equal OpportunityEmployer


ENGINEERS' TECH DATAEm NEN =NI is mio s s

ANTENNAS, TOWERS, & TRANSMISSION LINES70. CCA-Data sheet provides information about the CCA-FMA-

6710R FM circularly polarized antenna.71. DELHI-Twelve-page catalog concerns towers and masts

for Citizens -band and similar applications.72. JAMPRO-JCP series of circularly polarized FM transmitting

antennas is subject of catalog.

AUDIO EQUIPMENT

73. ATLAS SOUND-Catalog 566-67 contains illustrations andspecifications of public-address speakers, microphone stands,and accessories.

74. ELECTRO-VOICE - Microphones, public-address speakers,and accessories are shown in Catalog 167.

75. GATES-Sixteen-page booklet, "The Most Complete Line ofConsoles From Gates," presents information about line of

audio consoles.76. QUAM-NICHOLS-Catalog 67 provides information about

speakers for public-address, background -music, general -re-placement, and other applications.

77. STANFORD INT'L-New 1968 catalog of MB (West German)microphones and headsets is offered.

78. SUPERSCOPE-31-page catalog "All the Best From Sony"features Sony/Superscope tape recorders, magnetic tape,microphones, and accessories. Additional catalog has tech-nical specifications and retail prices of consumer and pro-fessional microphones.

79. SWITCHCRAFT - Bulletin 172 describes battery -operatedstudio mixer, "Studio MixMASTER'' Model 307TR.

80. UNITED RADIO SUPPLY-Specifications and block diagramof the Kustom Electronics broadcast console are available.

81. VEGA-Syncron S-10 cardioid condenser microphone is sub-ject of brochure.

CATV EQUIPMENT

82. AEL-Short-form catalog is titled -Colorvue Advanced De-sign CATV Distribution Equipment."

83. AMPHENOL-Four-page brochure describes line of trans-mission and drop -line cable for CATV applications.

84. DYNAIR-Data sheet is about Series -4000 solid-state mod-ular CATV demodulator, heterodyne converter, and audio -video modulator.

COMPONENTS & MATERIALS

85. BELDEN-56-page Catalog 867 covers lines of electronicwire and cable.

86. BRADY-Bulletin 100.1 describes pocket-size book of ad-hesive wire markers and matching terminal markers.

87. CHERRY-Series of "Snap/Reed" switches for low -energyswitching is featured in brochure.

88. DIALIGHT-Catalog Sheet L-206 depicts indicator lightsaccommodating incandescent T-2 bulb with telephone slidebase; Sheet L-207 depicts transistorized indicator light forintegrated circuits.

89. MAGNECRAFT-Catalog 268 shows general- and special-purpose relays; Product Data Bulletin 671 shows Class 88Kpower switching relay.

90. SCANBE-Panels, drawer slides, handles, circuit cards, card -mounting components, and other hardware items are in-cluded in eight -page catalog.

91. TROMPETER-Catalog M-4 gives information on line of coax,twinax, and triax matrix and multipole, multithrow switches.

92. WESTINGHOUSE-Electrical and mechanical characteristicsof line of plastic -encapsulated semiconductor rectifiers arepresented in 12 -page illustrated booklet.

93. ZERO-Twelve page Catalog SS -67 offers line of RFI-shieldedvertical, slope -front, and low -silhouette "Space Series" elec-tronic enclosures.

LIGHTING EQUIPMENT

94. COLORTRAN - ColorTran News, Issue 3, has applicationstories of interest to the motion -picture and television in-dustries.

"Want a Good Jobin Broadcasting?

You'll Need aFirst Class FCC License."Matt Stuczynski knows. He's the Senior Transmitter Operator ofRadio Station WBOE. His story is typical of hundreds of men whohave used Cleveland Institute Training as a springboard to successin Broadcasting. Here's what Matt says about Cleveland Institute:

"I give Cleveland Institute credit for my First Class FCC License.Even though I had only 6 weeks of high school algebra, CIE'sAUTO-PROGRAMMEDTm lessons really made electronicstheory and fundamentals easy. After completing the CIE course,I took and passed the First Class Exam. I now have a good jobin studio operation, transmitting, proof of performance, equip-ment servicing. Believe me, a Commercial FCC License is a`must' for a career in Broadcasting."

If you want rapid advancement in broadcasting, the first step is aFirst Class FCC ticket with your name on it. And Cleveland Insti-tute Home Study is a fast, economical way to get one. What's more,CIE backs their licensing programs with this money -back warranty:

"A CIE License Course will quickly prepare you for a FirstClass FCC License. If you complete the course but fail to passthe exam on your first attempt, CIE will refund all tuition."

With Cleveland Institute you get your First Class FCC License oryour money back! Send coupon today for FREE book or write toCleveland Institute of Electronics, 1776 E. 17th St., Dept. BE -40Cleveland, Ohio 44114.

ENROLL UNDER NEW G.I. BILLAll CIE courses are available under the new G.I. Bill.If you served on active duty since January 31, 1955, orare in service now, check box in coupon for G.I. Billinformation.

MAIL COUPON TODAY FOR FREE BOOK

*CIE Cleveland Institute

of Electronics1776 East 17th Street, Cleveland, Ohio 44114

Please send me your FREE book, "HowTo Get A Commercial FCC License."

Name

Address

City State 71p

(please P.M)

Occupation Age

Veterans check here for GI Bill informationAccredited Member National Home Study CouncilA Leader in Electronics Training . . . Since 1934 BE -40

October, 1967


73

DUE ToTECtiN (CAL

DIFFICULTY THISSTATION 4-4AS

TEMPORARILYLOST TfIE AUDIO

PORnON OF THE SHOW

If you'rekeepingAM, FM, and

TV signalsall to yourself...

something's wrong!When you need help, count on RCA Service Company, gearedthrough experience to broadcasting's special needs for main-tenance of complex station equipment. Getting the signal toyour audience requires equipment in top condition. RCA Broad-cast Service -sees to that. With a background unmatched in theindustry for this kind of work, RCA offers broadcasters protec-tion they can count on -on a contract or per call basis.Check some of the services available:Camera ChainsVideo Tape Recorder ServiceTV Camera and Transmitter

OverhaulInstallation SupervisionMicrophone and Pickup RepairsTransmitter Performance

Measurements

Antenna InspectionMeasurements

Console RepairsMicrowave ServiceTV Projector ServiceCustom FabricationTeletypewriter Maintenance

To protect performance of your equipment, call our field office near youlOr contact Broadcast Service, RCA Service Company, Bldg. CHIC -225,Camden, N. J. 08101. Phone: ( 609) 963-8000, ext. PH -328.

The Most Trusted Name in Electronics

95. MOLE-RICHARDSON-Supplement No. 1 to Catalog K illus-trates seven new quartz lighting fixtures and several otherproducts. Twenty -page price list for the company's productsalso is available.

96. PACKAGED LIGHTING SERVICES-Descriptive catalog oflighting equipment includes quartz -iodine conversion unitsfor existing studio spotlights and scoops.

MICROWAVE & STL EQUIPMENT

97. MICROLINK / VARIAN - Company offers description andspecifications of new TVL Series TV relay equipment.

98. RHG ELECTRONICS-Solid-state FM microwave relay equip-ment is listed in eight -page Catalog 67b.

MISCELLANEOUS

99. TEXAS ELECTRONICS-Specification sheet is about Model445 indicating and recording system for wind direction andvelocity.

100. WALLACH-Storage-cabinet brochure includes data on newcabinet for storage of three-inch tape boxes.

RECORDING & PLAYBACK EQUIPMENT

101. AMPEX-Case histories are related in Bulletin G195, aboutthe Cue-Matic audio recorder, and Bulletin G228, about in-structional use of broadcast and closed-circuit video-taperecording equipment. Also offered is Bulletin V119 onMultilock system synchronizer for synchronous operation oftwo or more audio or video recorders.

102. CROWN INT'L-Four-page brochure gives information aboutCrown Pro 800 recorders with computer -logic transport con-trol.

103. JOA-Data and prices for new tape cartridges and recondi-tioning services are offered.

104. METROTECH-Six-page brochure describes 500 Series re-corders, reproducers, and slow -speed loggers.

allmirrixsNEW!!

UD-865

Uni-DirectionalDynamicMicrophone

Designed for use at broadcastingstations, music stages and suit-able for hi-fi recording.63 *Tour.

o

a; -10-7-7-207;

-cr IC/ 20 r 50 00 200 500 55 105 20:

SPECIFICATIONS:*Cartridge: DM -33F requency Response

50-15,000 cps ± 5dBIm pedance: 600n ,50k n*Sensitivity:

-72dB!-53dB ± 3dBDimensions:

341 x 160m/m

For further information please write to

PRIMO COMPANY LTD.Head Office: 25.1.6.chorne Ml/f0 MitAdShi Tokyo, Japan Tel 0422-43.3121-6

Cable Pbrno Musashino Pol,taka" Telex 2822 326 PRIMO MUSChicago Illinois Office: A P T No 204, 530 W Surf. St . Chicago Illinois 60657.

U.S.A. Tcl. 312.472.61421 Telex: 25.4225 PRIMO MUS CGOILLUSA



105. RAYCO-BASF magnetic tape in "Perma-Store" library boxis illustrated in information sheet.

106. SPARTA-Series R-310 professional tape recorders are sub-jects of information sheet.

107. TELEX-Magnecord Model 1021 for monophonic and Model1022 for stereophonic recording are described in brochure.The Viking Model 230 tape transport is subject of additionalmaterial.

REFERENCE MATERIAL & SCHOOLS

108. CLEVELAND INSTITUTE OF ELECTRONICS - Pocket-sizeplastic "Electronics Data Guide" includes formulas andtables for: frequency vs wavelength, dB, length of antennas,and color code.

TELEVISION EQUIPMENT

109. ALLEN AVIONICS-Catalog of delay lines and filters forvideo and pulse applications is available.

110. BURKE & JAMES-Eight-page publication provides list of

lenses for television use.111. CLEVELAND ELECTRONICS - A 52 -page quick -reference

step-down die -cut catalog gives information on vidicon,Plumbicon, and image -orthicon deflection components.

112. COHU-Data sheets are for 9840 Series color video encoder,2610/2620 Series chroma detector, and 3207 Series self-con-tained Plumbicon cameras.

113. COLORADO VIDEO-Descriptive sheet for Model 301 VideoAnalyser, for displaying TV waveforms on picture monitor,is given.

114. KALART-Literature package includes material on Kalart/Victor 16 -mm TV projector, Tele-Beam large -screen TV pro-jector, 16 -mm sound motion -picture projectors, and projectionTV in the schools.

115. KAPPA-Catalog DL -1&10A lists video cable simulators andother electromagnetic delay lines.

116. TELEMATION-Four-page, two-color brochure presents Mod-el TMV-600 Cablecaster video control center for CATV andsimilar applications.

117. VITAL-Literature describes Model VI -500 color stab ampwith AGC, and Models VI -10A and VI -20A video and pulsedistribution amplifiers; new features are listed.

118. WARD-Brochure tells about TS -200 solid-state vertical -inter-val video switching systems.

TEST & MEASURING EQUIPMENT

119. BALLANTINE-Solid-state AC voltmeter, Model 303, is shownin specification sheet.

120. B & K-Bulletins are available for the following instruments:Model 2409 AC voltmeter/amplifier; Model 4240 simulatedvoice mechanism, for testing telephone transmitters andhandsets; Model 2410 AF voltmeter/amplifier; Model 2417rms voltmeter; Model 2006 heterodyne voltmeter; and Model3350/51 electroacoustic transmission measuring system, fortests on telephone handsets.

121. DELTA-Literature has as its subject the Model RG-1 solid-state receiver/generator for use with impedance bridges inantenna -system measurements.

122. HEWLETT-PACKARD - Eight -page brochure, "Cable FaultLocating Instruments," details the use of electronic instru-ments in the maintenance of cable plants.

123. TEKTRONIX-Information is offered on Type 526 TV vector -scope, Type 529/RM529 TV waveform monitors, TV acces-sories, and TV vertical -interval test signals.

124. TV ZOOMAR-Fliers show TV Colorgard meter for balancingcolor TV monitors, "Newsbreaker 400" color -film processor,and HTS studio equipment.

TRANSMITTERS & ASSOCIATED EQUIPMENT

125. BAUER-Catalog sheet gives information and specificationson Model FB-l0J 10,000 -watt AM transmitter.

Help stamp outdropouts Clean

tape headswithMS -200"Oxide dust on tape heads and helical scanrecorders is a frequent source of dropouts.Some engineers still clean them thehard way, with Q -tips, but many have founda better way: MS -200 Magnetic TapeHead Cleaner. MS -200 sprays away dustand dirt in seconds. You can even applyit safely while the tape is on the air. Finally,users report more than twice as manypasses of tape between cleanings withMS -200 as with swabs. Recommended byleading tape manufacturers.Write on letterhead for literature andfree sample.

miller-stephensonchemical co., inc.ROUTE 7, DANBURY, CONNECTICUT*U.S. and foreign patents pending


October, 1967 75

a

sound

momfor the BroadcastIndustry...

REMOTE CONTROLMIKE REELS

Specially designed reels. Remotecontrol by drum, push button orstation relay. 115 volt reversiblechain driven motor. 2 to 8conductor slip rings available.150' cable capacity.

POWER CABLEREELS

I.E.R.'slevel windPort -O -Reelsprotect andprevent mikeor extensioncord break-downs. Up to400' cablecapacity.

Write for Specification Data on themost complete line of RemoteControl Reels and Port -O -Reels.

INDUSTRIAL

ELECTRIC

REELSINCORPORATED

1503 CHICAGO ST.OMAHA, NEBRASKA 68102

Advertisers' Index11.1111 ME MEI MIN

Alford Manufacturing Co. 67Allen Avionics 60Applied Electro Mechanics, Inc. 64Ball Bros. Research Corp. 51Bauer Electronics Corp. 63Belar Electronics Lab. 38Belden Mfg. Co. 24, 25, .55Broadcast Electronics, Inc. 56, 66. 76CBS Laboratories, Div. of CBS, Inc 5CCA Electronics Corp. 6Central Dynamics Corp. 45Cleveland Institute of Electronics 73Cohu Electronics. Inc. 3Collins Radio Co. 66Dresser Crane, Host & Tower Div. 71Fairchild Recording Equipment Corp. 6Gates Radio Co. 9Greenlee Tool Co.. Division of

Greenlee Bros. & Co. 63Industrial Electric Reels. Inc. 76International Nuclear Corp. Cover 3ITT Federal Electric Corp. 35Jampro Antenna Co. 41JOA Cartridge Service 69Lang Electronics, Inc. 69Lenkurt Electric Co., Inc. 70l.ipsner-Smith Corp. 62London Co. 63Memorex Corp. 40Metron Instruments, Inc. 76Mliler-Stephensen Chemical Co. 75Minneapolis Magnetics, Inc. 62Morhan National Sales 40North American Philips Co., Inc. 43Philips Broadcast Equipment Corp. 49Photo Research Corp. 66Primo Co., Ltd. 71RCA Electronic Components &

I ievices Cover 4RCA Broadcast & Communications

Products 26, 29RCA Service Co. 74Richmond Hill Labs, Inc. 52Riker Video Industries, Inc. Cover 2Round 11111 Associates Inc 72Scully Recording Instruments Corp. 37Shure Bros.. Inc. 39Sparta Electronic Corp 60Stanton Magnetics 61Taber Mfg. and Engineering Co. 71Telemation. Inc. 64. 65Telemet Co. 56. 57Treise Engineering, Inc. 8Visual Electronics Corp. 59Ward Electronic Industries, Inc. 7Wilkinson Electronics, Inc. 67

SPOTMASTERSolid -State Portable

REMOTEAMPLIFIER

S

The RA-4CA is a lightweight, four -channelportable mixer amplifier specifically de-signed for remote broadcast or auxiliarystudio use. It is completely self-containedand operates from either AC or batteries(switching automatically to battery opera-tion if AC power fails); runs as tong as200 hours on low-cost "D" cells. It offersfour microphone channels with mastergain and P.A. feed, all controlled from thefront panel. Lightweight construction (just11 pounds with batteries), a convenientcarrying handle and a snap -on front covermean the RA-4CA can be easily set up tooperate anywhere. For further information,please write or call today:

BROADCAST ELECTRONICS, INC.8810 Brookville Road

Silver Spring, Maryland 20910Area Code 301 588-4983

711ro

AMMODULATION

MONITORThe Metron Model 506B-1 Amplitude Modula-tion Monitor is a high quality instrument, field -proven for several years.

FCC Type Approval 3-127

Compact-Only 51/4" high on astandard 19" rack

All solid state circuits-silicontransistors for greater reliability.

Low Cost-only $550.00.When you replace your present AM Monitor,buy the Metron 506B-1, your best value.

WietrOn METRON INSTRUMENTS, INC.1051 South Platte River Drive Denver, Colo. 80223


BROADCAST ENGINEERING76


Professional Services

VIR JAMESCONSULTING RADIO ENGINEERSApplications and Field Engineering

345 Colorado Blvd.Phone. (Area Code 303) 333-5562

DENVER, COLORADO 80206Member AFCCE

JAMES C. McNARYConsulting Engineer

National Press Bldg.

Washington 4, D. C.Telephone District 1-1205

Member AFCCE

CAMBRIDGE CRYSTALSPRECISION FREQUENCYMEASURING SERVICE

SPECIALISTS FOR AM -FM -TV445 Concord Ave. Phone 876.2810

Cambridge, Mass. 02138

AMPEX HEAD ASSEMBLY RECONDI-TIONING SERVICE for all Ampex pro-fessional model recorders. This profes-sional service features precision relap-ping of all heads for maximum head life.Your assembly is thoroughly cleaned andguides are replaced as required. Price in-cludes optical and electrical inspectionand complete testing on Ampex equip-ment in our plant. Full track or halftrack assemblies . . . $35.00. One to twoday service. "Loaner" assemblies avail-able if necessary. LIPPS, INC., 1630Euclid Street, Santa Monica, California90404. (913) EX 3-0449. tf

CRYSTAL AND MONITOR SERVICE - Fre-quency change and repair service for AMmonitors including G.R., RCA, Gates, W.E.,and Doolittle; also H -P 335B FM. AM moni-tors bought and sold. What have you, whatdo you need? New or regrinding of AMcrystals for RCA, Gates, Bliley, W.E., andJ -K oven holders, repairs, etc. Fastest serv-ice, reasonable prices. Over 25 years inthis business. Eidson Electronic Co., Box96, Temple, Texas 76501, Phone 817 773-3901.

2-67-tf

Kits serviced, shipped. Professional, reason-able. Also small broadcast rack and tableunits, carts, tuners, limiters. Write: 109Pinetree, Woodbridge, Va. 4-67-tf

VIDEO TAPE RECORDERAUDIO HEAD ASSEMBLY SERVICE

Precision relapping of all heads and sup-porting posts, including cleaning andtesting. Ampex head assembly with "cue"tracks, $75.00 complete. RCA units alsorelapped. One to two day service. LIPPS,INC., 1630 Euclid St., Santa Monica, Calif.90404. (213) EX 3-0449. tt

JOHN H. MULLANEYand ASSOCIATES

Suite 71,1150 Connecticut Ave., N.W.

Washington, D. C. 20036Phone 202-223-1180

Member AFCCE

ROSNER TELEVISION

SYSTEMSENGINEERS I CONTRACTORS120 E. 56 St.New YorkN. Y. 10022

230 Newtown Rd.PlainviewN. Y. 1 1803

Swift, professional service on your tapecartridge rebuilding needs. All work fullyguaranteed - virtually no audio dropoutwith our splicing technique! Write Broad-cast Equipment Rebuilders, Route 2, Box723, Connellys Springs, N. Carolina 28612.

10-67-tf

ClassifiedMEN INN =I

Advertising rates in the ClassifiedSection are fifteen cents per word.Minimum charge is $2.00. Blind boxnumber is 50 cents extra.

Equipment for Sale

CO -AXIAL CABLE Heliax, Styroflex, Spiro -line, etc. Also rigid and RG types in stock.New material. Write for list. Sierra -WesternElectric Co., Willow and 24th Streets, Oak-land, Calif. Phone 415 832-3527 5-66-tf

Television / Radio / communications gear ofany type available. From a tower totube. Microwave, transmitters, cameras,studio equipment, mikes, etc. Advise yourneeds-offers. Electroflnd Co., 440 ColumbusAve., NYC. 212 -EN -25680. 8-64 tf

CARTRIDGE TAPE EQUIPMENT

Completely reconditioned and guaranteed.Spotmaster Model 500 Record/Playbacks,$350.00. Model 505 Playbacks $250.00. 30 -day money -back guarantee on all equip-ment.

BROADCAST PRODUCTS COMPANY18804 Woodway Drive, Derwood, Maryland,

20855

(301) 926-4600 3-67-12t

Audio Equipment bought, sold traded.Ampex, Fairchild, Crown, McIntosh, Viking.F. T. C. Brewer Company, 2400 West HayesStreet, Pensacola, Florida. 3-64-tf

50,000 connectors SO 239, PL 259, F-59,F-61-also cable assemblies. Manufacturer'sover stock. AVA Electronics & MachineCorp., Box 224, Upper Darby, Pa. 10-67-1t

Everything in used broadcast equipment.Write for complete listings. BroadcastEquipment and Supply Co., Box 3141, Bris-tol, Tennessee. 11 -64 -if

"AUDIO EQUIPMENT - Whatever yourneeds, check us first. New and used. Am-pex, Altec, AKG, EV, Fairchild, Neumann,Langevin, Rek-O-Kut, Uher, Viking. Sendfor equipment list." Audio Distributors,Inc., 2342 S. Division Ave., Grand Rapids,Michigan 49507. 6-66-tf

Spring hanger (53) for 3" or 31/4" trans-mission line, noninsulated. TCA Tower Co.,4325 Bankhead Hwy., Mableton, Georgia30059 9-67-2t

Large selection of good -quality surplusequipment including distribution ampli-fiers, power supplies, stab amps, audioequipment, telop projector, master moni-tors, image orthicon tubes, CRT tubes,camera cable, and many other items. Forcomplete list, write Box 182, Broadcast En-gineering. 9-67-2t

New turntables, tone arms, preamplifiers,cartridge machines, equalizers, tape re-corders, studio equipment. Professionalbrands. Write for special offers. We buy,sell, trade, lease. Audiovox, P. 0. Box 7067,Ludlam Branch, Miami, Fla. 33155. 9-67-tf

Complete UHF Package. TTU-1B RCA Trans-mitter, Filterplexer & TFU-24DL Antenna(Ch. 24). Sync Generator, TI{ -10 Live Cam-era, Dage Vidicon Film Camera, 2 HolmesLTD 16mm Projectors, 2 RCA TP 16 FilmProjectors, 35mm Dual Slide Projector, allassociated input gear to build a completestudio transmitter. For further information,contact: H. J. Eskew, Chief Engineer, WICDTelevision, Champaign, Illinois. Phone: Area217, 352-7673. 10-67-1t

TTU-1B RCA Transmitter, Filterplexer,TFU-6 RCA antenna (Ch. 331 General RadioStation Monitor. For further information,contact: H. J. Eskew, Chf. Eng., W3CD Tel-evision, Champaign, Illinois. Phone: Area217, 352-7673. 10-67-1t

October, 1967 77

Equipment for Sale(Continued)

For Sale: RCA TT2BH Transmitter now onCh. 13, $15,000. Sideband & harmonic filtersalso available. Contact H. L. VanAmburgh,C.E., WGAN-TV, Portland, Maine, 207 772-4661 for details. 10-67-1t

Receive pictures from APT Weather Satel-lites. Limited supply of facsimile machinesfor receiving high quality (8x8") pictures.Like new, complete, fully guaranteed. Low-est price anywhere. For complete details,write: Newsome Electronics, Dept. S, 2670Pinetree, Trenton, Michigan 48183. 10-67-1t

For Sale: Gates SA -39 peak limiting ampli-fier. Just taken out of service. Good condi-tion. $195. Joe Brewer, WZYX, Cowan,Tennessee. 10-67-1t

Equipment Wanted

We need used 250, 500, 5K & 10K WattsAM Transmitters. No Junk. GuaranteeRadio Supply Corp., 1314 Iturbide St.,Laredo, Texas 78040. 3-66-tf

Complete instruction manual for DumontTelevision Transmitter, Series 9000 in goodcondition. Write to Leo Voien, Box 2512,Sioux City, Iowa 51106. 9-67-2t

SPOTMASTERS WANTED-Model 500 Re-cord/Playbacks and Model 505 Playbacks.Send full details to: BROADCAST PROD-UCTS COMPANY, 18804 Woodway Drive,Derwood, Maryland 20855 (301) 926-4600.

10-67-6t

Employment

IMMEDIATE OPENINGS-Qualify for anyof the following positions: Technicians forRCA Closed Circuit Television equipment,Cameramen, Maintenance men. Video Tapemen, Video Engineers. RCA Rep. 143-08 94thave., Jamaica, New York, or (212) 297-3344.

7-87-tf

Wanted: Experienced first ticket to assumeassistant chief position. All fringe benefitsand top monetary compensation. Stationconverting to color. Apply-R. Vincent,Manager, KCND-TV, Box__ 191, Pembina, N.Dakota. 701-825-6292. A McLendon station.

8-67-3t

TV engineer with first class license inter-ested in gaining knowledge through experi-ence with latest high band color video tapeequipment and Plumbicon color cameras.Equipment on hand and installation tocommence within a few weeks. Get in onthe beginning. Call the Chief Engineer col-lect, 313-239-6611. 8-67-tf

Electrical Engineers needed immediately forTV/Radio stations, manufacturers, andCATV for all positions. Send well preparedresume to Nationwide Broadcast PersonnelConsultants, 645 North Michigan Avenue,Chicago, Illinois, 60611. We have openingsfor all qualified applicants and the em-ployer pays our fee. 10-67-tf

REGIONAL SALES MANAGER-EASTNation's leading supplier of time -weather,hews, and local origination equipment forCATV seeks top-notch sales engineer type.CATV background not necessary, but goodunderstanding of video systems equipmentdesired. Excellent opportunity for willing -to -travel go-getter. Contact: Mr. K. D. Law-son, Sales Mgr., TeleMation, Inc., 2275 SouthWest Temple, Salt Lake City, Utah 84115,(801) 486-7564. 10-67-1t

Immediate opening for Broadcast Engineer.\ 1 I color station, second class license orbetter required. Send resume to WNYS-TVChannel 9, Syracuse, Inc. P.O. Box 9,

Syracuse, N.Y. 13214. 10-67-tf

Job Headquarters for all Radio and Tele-vision Engineers. Immediate openings existin 9 western states and elsewhere for qual-ified engineer and technical personnel. Allcategories from trainees to experiencedtransmitter maintenance, chief, assistantchief, live color video maintenance andtechnical operations. Send us your com-plete resume now. The AMPS Agency, 3924Wilshire Blvd., Los Angeles, California90005. Telephone DU 8-3116.By Broadcasters-For Broadcasters 11-66-tf

Radio Station KTRM in Beaumont, Texason the Gulfcoast has an opening for 1stClass Engineer. Preferably with sometechnical experience. No board work. Phone713-892-4990 between 2 PM & 12 midnight.Ben Hughes, Chief Engineer. 10-67-1t

IMMEDIATE OPENINGS for experiencedcontrol room and transmitter engineers.Top pay scale and all fringe benefits.Miami's first full -color TV Station. WriteR. Paasch, CE, Channel 7, P.O. Box 1118,Miami, Fla. 33138. 10-67-1t

Business Opportunities

UNUSUAL OPPORTUNITYFor a growing manufacturing firm, to ac-quire valuable patents and trade markrights on latest accessories for large andsmall recording tape and movie film.SPECIAL point -of -sale package. SPECIALreel, etc. P.O. Box 01141, Cleveland, Ohio44101. 8 -67 -St

Training

To advance in electronics, knowledge andability are required. Grantham offers cor-respondence and resident instruction, indepth, leading to the degree of Associate inScience in Electronics Engineering. G.I. Billapproved. Credit for previous training andexperience allowed. Free Catalog. Write:Dept. E-2, Grantham School of Electronics,1505 N. Western Ave., Hollywood, California90027. 6-67-tf

Miscellaneous

RADIO AND TELEVISION STATIONS forsale in all parts of United States. Qualifiedbuyers may receive further details bywriting to Inter -Media CommunicationsCorporation, 246 Fifth Avenue, New York,New York 10001. 1-67-121

Technical

WESTERN MICHIGAN-Immediate openingsfor Television Control Room Engineers.Excellent fringe benefits; good pay; NBCaffiliate; full color facilities. Phone collect,or write: MR. CHARLES F. ROBISON, ChiefEngineer, WOOD TV, Grand Rapids, Michi-gan 616-459-4125. 10-67-3t

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