technician license class gordon west technician class manual pages 115-121 weak signals presented by...

Technician Technician License License ClassClass

Gordon West Gordon West Technician Class Technician Class

ManualManualPages 115-121Pages 115-121

Weak SignalsWeak Signals

Presented byPresented by

Heart Of Texas Heart Of Texas Amateur Radio ClubAmateur Radio Club

(HOTARC)(HOTARC)

Weak SignalsWeak Signals 22

Let’s Review…FrequencyLet’s Review…Frequency

Remember:Remember:– kilo-kilo- means 1,000 (thousand), as in means 1,000 (thousand), as in kkHzHz– Mega-Mega- means 1,000,000 (means 1,000,000 (mmillion), as in illion), as in MMHzHz– Giga-Giga- means 1,000,000,000 (billion), as in means 1,000,000,000 (billion), as in GGHzHz


FrequencyFrequency

MF (Medium Freq.): 300 kHz – 3 MHzMF (Medium Freq.): 300 kHz – 3 MHz

HF (High Freq.): 3 MHz – 30 MHzHF (High Freq.): 3 MHz – 30 MHz

VHF (Very High Freq): 30 MHz – 300 MHzVHF (Very High Freq): 30 MHz – 300 MHz

UHF (Ultra High Freq): 300 MHz – 3 GHzUHF (Ultra High Freq): 300 MHz – 3 GHz

““Microwaves”: generally above 500 MHz Microwaves”: generally above 500 MHz (or 0.5 GHz)(or 0.5 GHz)


Radio FrequenciesRadio Frequencies

The FCC allows amateur radio operators to The FCC allows amateur radio operators to transmit transmit only in 27 specific “windows.”only in 27 specific “windows.”

Most Technicians primarily use their voice Most Technicians primarily use their voice privileges in VHF and UHF.privileges in VHF and UHF.


Radio SignalsRadio Signals

Pages 115 – 119…Pages 115 – 119…

Key words:Key words:

– Curvature of the earthCurvature of the earth

Let’s look at this “curvature of the earth” Let’s look at this “curvature of the earth” thing…thing…

Weak Signals 6

How Radio Waves TravelHow Radio Waves TravelLine-of-sight: the antennas can “see” each other. Your radio signals are heard!

Beyond about 7-8 miles, signals are blocked by the curvature of the earth…the “radio horizon.”

YOU

Waco Bellmead

Weak Signals 7

How Radio Waves TravelHow Radio Waves Travel

To talk to a station beyond the radio horizon, beyond the line-of-sight, a “repeater” mounted up high can relay your radio signals.

YOU

Waco Dallas

Weak Signals 8


Some radio waves can reflect off the ionosphere (about 100-200 miles up) and travel hundreds of miles.

YOU

Waco Memphis

Ionosphere

Weak Signals 9


Radio waves can even reflect more than once and sometimes travel long distances around the world!

WacoParis

YOUIonosphere

Weak Signals 10


Signals can also be relayed by satellite or even reflected off of the moon! Reflection off the ionosphere is affected by radiation from the sun. So, radio operators often monitor the solar conditions, and note the time of day.

Solar radiation

Ionosphere


T9 B04 (pg 115)T9 B04 (pg 115)What is the radio horizon?What is the radio horizon?A.A. The point where radio signals between two points The point where radio signals between two points

are blocked by the curvature of the Earthare blocked by the curvature of the EarthB.B. The distance from the ground to a horizontally The distance from the ground to a horizontally

mounted antennamounted antennaC.C. The farthest point you can see when standing at the The farthest point you can see when standing at the

base of your antenna towerbase of your antenna towerD.D. The shortest distance between two points on the The shortest distance between two points on the

Earth's surfaceEarth's surface

Notice the similar point is stressed in the next Notice the similar point is stressed in the next question (B11).question (B11).


T9B11 (pg 115)T9B11 (pg 115)Why do VHF and UHF Radio signals usually Why do VHF and UHF Radio signals usually travel about a third farther than the visual line of travel about a third farther than the visual line of sight distance between 2 stations?sight distance between 2 stations?A.A. Radio signals move somewhat faster than the Radio signals move somewhat faster than the

speed of light and travel farther in the same amount speed of light and travel farther in the same amount of timeof time

B.B. Radio waves are not blocked by dust particlesRadio waves are not blocked by dust particles

C.C. The Earth seems less curved to radio The Earth seems less curved to radio waves than to lightwaves than to light

D.D. Radio waves are blocked by dust particlesRadio waves are blocked by dust particles


VHF and UHFVHF and UHF

See pages 117 – 119…See pages 117 – 119…

Key words:Key words:

– Shorter wavelengths (Shorter wavelengths (penetratingpenetrating power) power)

– Single SidebandSingle Sideband

Let’s think again about those upper frequency Let’s think again about those upper frequency bands that you can use…bands that you can use…


VHF & UHF BandsVHF & UHF Bands

UHFshorterwavelengths

Closer to “micro-wavelengths”

More energy—”punches” right through the atmosphere

1240 1300

902 928

420 435 438 450 Satellite

5 MHz repeater frequency separation (Split)

219 220 222 225 Digital

Mssging

144 144.1 148

CW 600 kHz repeater frequency separation (Split)

50 50.1 54 CW

V H FV H F

U H FU H F


T9 B06 (pg 117)T9 B06 (pg 117)Why do UHF signals often work better Why do UHF signals often work better insideinside of of buildings than VHF signals?buildings than VHF signals?A.A. VHF signals lose power faster over distanceVHF signals lose power faster over distance

B.B. The The shorter wavelengthshorter wavelength of UHF signals of UHF signals allows them to more easily allows them to more easily penetratepenetrate urban areas and buildingsurban areas and buildings

C.C. This is incorrect; VHF works better than UHF inside This is incorrect; VHF works better than UHF inside buildingsbuildings

D.D. UHF antennas are more efficient than VHF UHF antennas are more efficient than VHF antennasantennas


PropagationPropagationReflection and Multi-path InterferenceReflection and Multi-path Interference


T9 B10 (pg 117)T9 B10 (pg 117)

What term is commonly used to describe the What term is commonly used to describe the rapid fluttering soundrapid fluttering sound sometimes heard from sometimes heard from mobile stations that are moving while mobile stations that are moving while transmitting?transmitting?

A.A. Flip-floppingFlip-flopping

B.B. Picket fencingPicket fencing

C.C. Frequency shiftingFrequency shifting

D.D. PulsingPulsing

Just remember this unusual answer!


T9B02 T9B02 (pg 117)(pg 117)

What might be happening when we hear a VHF What might be happening when we hear a VHF signal from long distances?signal from long distances?A.A. Signals are being reflected from outer spaceSignals are being reflected from outer space

B.B. Someone is playing a recording to usSomeone is playing a recording to us

C.C. Signals are being reflected by Signals are being reflected by lightning storms in our arealightning storms in our area

D.D. A possible cause is A possible cause is sporadic E reflection from sporadic E reflection from a a layer in the ionospherelayer in the ionosphere


T6 A04 (pg 118)T6 A04 (pg 118)

Which type of voice modulation is most often Which type of voice modulation is most often used for long distance and weak signal contacts used for long distance and weak signal contacts on the VHF and UHF bands?on the VHF and UHF bands?

A.A. FMFM

B.B. AMAM

C.C. SSBSSB

D.D. PMPM

Let’s look at what we mean by sideband…Let’s look at what we mean by sideband…

Single Sideband!


What is Meant by “What is Meant by “Sideband?Sideband?””AMAM stands for stands for AAmplitude mplitude MModulationodulation

AM signals are almost 10 kHz wide—lots of spectrum.AM signals are almost 10 kHz wide—lots of spectrum.– Carrier in the middle Carrier in the middle

(e.g., (e.g., 1230 kHz1230 kHz for KRZI) for KRZI)– Upper and lower Upper and lower sidebandssidebands

(identical, but mirrored)(identical, but mirrored)

To create “To create “SSingle ingle SSideideBBand”and”– Carrier is suppressedCarrier is suppressed– One sideband is suppressedOne sideband is suppressed

(usually the lower one)(usually the lower one)– More power can be sent in More power can be sent in

the much narrower signal.the much narrower signal.


T6 A07 (pg 118)T6 A07 (pg 118)

Which sideband is normally used for VHF and Which sideband is normally used for VHF and UUHF SSB communications?HF SSB communications?

A.A. UUpper sidebandpper sideband

B.B. Lower sidebandLower sideband

C.C. Suppressed sidebandSuppressed sideband

D.D. Inverted sidebandInverted sideband

Note: Above 10 MHz, always use Note: Above 10 MHz, always use UUSB (upper).SB (upper).


T5D11 T5D11 (pg 118)(pg 118)

What may be the problem if another operator What may be the problem if another operator reports that your SSB signal is very garbled and reports that your SSB signal is very garbled and breaks up?breaks up?A.A. You have the noise limiter turned onYou have the noise limiter turned on

B.B. The transmitter is too hot and needs to cool offThe transmitter is too hot and needs to cool off

C.C. RF energy may be getting into the RF energy may be getting into the microphone circuit and causing feedbackmicrophone circuit and causing feedback

D.D. You are operating on lower sidebandYou are operating on lower sideband


T9B01 T9B01 (pg 119)(pg 119)

Why are VHF/UHF signals Why are VHF/UHF signals notnot normally normally heardheard over long distances?over long distances?A.A. They are too weak to go very farThey are too weak to go very far

B.B. FCC regulations prohibit them from going more than FCC regulations prohibit them from going more than 50 miles50 miles

C.C. VHF and UHF signals are usually VHF and UHF signals are usually notnot reflectedreflected by the ionosphere by the ionosphere

D.D. They collide with trees and shrubbery and fade outThey collide with trees and shrubbery and fade out


T1C09 T1C09 (pg 120)(pg 120)

What do the FCC What do the FCC rulesrules mean when an amateur mean when an amateur frequency band is said to be available on a frequency band is said to be available on a secondary basis?secondary basis?A.A. Secondary users of a frequency have equal rights Secondary users of a frequency have equal rights

to operateto operate

B.B. Amateurs are only allowed to use the frequency at Amateurs are only allowed to use the frequency at nightnight

C.C. Amateurs may not cause harmful Amateurs may not cause harmful interferenceinterference to primary users to primary users

D.D. Secondary users are not allowed on amateur bandsSecondary users are not allowed on amateur bands


Grid Square MapGrid Square Map

Waco, TX EM11


T7A09 T7A09 (pg 120)(pg 120)

What is a grid locator?What is a grid locator?

A.A. A letter-number designator assigned to a A letter-number designator assigned to a geographic locationgeographic location

B.B. Your azimuth and elevationYour azimuth and elevation

C.C. Your UTC locationYour UTC location

D.D. The 4 digits that follow your ZIP codeThe 4 digits that follow your ZIP code

Waco, TX Is EM11Waco, TX Is EM11


T7A11 T7A11 (pg 120)(pg 120)

What is the maximum power allowed when What is the maximum power allowed when transmitting telecommand signals to radio transmitting telecommand signals to radio controlled models?controlled models?A.A. 500 milliwatts500 milliwatts

B.B. 1 watt1 wattC.C. 25 watts25 watts

D.D. 1500 watts1500 watts


T7A12 T7A12 (pg 121)(pg 121)

What is the station identification requirement What is the station identification requirement when sending commands to a radio control when sending commands to a radio control model using amateur frequencies?model using amateur frequencies?A.A. Voice identification must be transmitted every 10 Voice identification must be transmitted every 10

minutesminutesB.B. Morse code ID must be sent once per hourMorse code ID must be sent once per hour

C.C. A label indicating the licensee's A label indicating the licensee's call signcall sign and addressand address must be affixed to the must be affixed to the transmittertransmitter

D.D. There is no station identification requirement for this There is no station identification requirement for this serviceservice

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