A U*S NAVALITECHNICiUIION* IN EUROPE

~~i. TECHNICAL REORT NO. 417-45-

GEH.- AA4

ANDAA 106 MINE UNITS

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U. S. NVAL MNIEAL °SSION IN R 1RP2c/o Fleet Post Office

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Serial: 01153 -.

25 September 1945.

Frcm: Chief, U.S. Naval Technical Mission in Europe.To Chief of Naval Operations (OP-l64P"").

-q Subjct: U.S. Naval Technical 1ission in Europe TechnicalRoport No. 417-45, German AA4 and m, 16 }ino 1..-6units - Forvardinig of.

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-nclosures: (A) (F-'.) F6ur (4), comlete copies of subject reportas listed in distribution.

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2. CNO (OP-16--T) is requostod to mako complote addit-ional copios of this roport for foirarding to such other agenciosas may be interested. -. -

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TECHNICAL IMPORT N. 417-45

UNANNOUNCEDGRAN AA 4 MID AA 106 MINE UNITS

SULMM±AiY

This report contains information on the German AA 4 ".-.and AA 106 mine firing units. These units are combinedacoustic-supersonic operated devices. AA 4 was designedto be used in the W and SiA mines. The AA 106 wasdesigned to be used in the Bit, 1000 H and &, 1000 L mines.Both reached development stage, but were not producednor used operationally during the war. -

September 1945".... ..

U. S. NAVIL TECHNICAL IISSION IN EUROPE -DTIC. AUG 3 1984

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TABLE OF CONTNTS

l. Introduction 32'. General 33;AA 4 4

' AA4l Circuits . 45. -A. 106 Acoustic, Triggering Circuit 56i.AA 106-Supersonic Receivers- 57. AA i06. ,Float, and Float Release, 5&8. AA;1 06 Arming 69. jAAj i06 Triggering

10. AA 106 Amplifier I 7 e-;11. ,A .106 Amplifier IT 712. AA 106 Fiing Circuit 713 AA 106 P.Sa..,&.Anti-Leak Device 8 .

14i .. t,:106. Remarks 8,*.' .,".

LIST OF ILLUSTR,.TIONS -Z

1. Schematic Drawing h4 Heceivzrs and Amplifior 9System.

.2-. Characteristics of hA 106 Receivers 10 .3. i,,ounting of Ali 106 Float in B a 1000 H or Bi 11

1000 L .inc.4. AA 106 Receivers Reaction to Ship Transit at 12

11 kts.5, AA 106 Receivers Reaction to Ship Transit at 1320 .kts. •. :

6. 1A\ 106 Receivers Reaction to Ship Passing .20 14! meters Abeem, with Noise -Buoy..

7-: .AA 106 Circuit Diagram. 15

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GERMAN AA 4 AND AA 106 mINE UNITS .

1. Introduction.

(a) Part of the German mine development program was directedto work on supersonic fired mines. At the end of th. war in Europefour supersonic units were wider development, and of these one ....

Tj[ (AA 4) had been abandoned. The units were designated AE 1, AA 4,AE 101 and AA 106. Of these., the AE~ 1and AE 101 are active.("pinging") supe-rsonic units. The AA 4 and AA 106 are passivedirectional supersonic units. This report will be confinedto the passive units. The active unitt are reported separately , '- ..in NavTechMisEu Technical Report No. 290-45.

(b) Very little material has been captured, but considerable. documentary information is available, and microfilm negatives

of these documents have bon forwarded to U.S.. The informationcontained herein has beon obtained through field exarination-ofmaterial, preliminary screcning of documents, and intcrrogation ofGerman prisoners of war.

2. General.

The German AA 4 and AA 106 are directional supersonic minefiring units. Due to the directional requirements, self- ,orienting properties are necessary to thu directional elements.At first, SVK attempted to mount a group of di.rectional magneto- ' "strictive receivers (7 in number) in a bolt around an LUI minecase. The top-most receiver was selected for operation by aweighted internal pendulum switch, This was unsuccessful. Inthe case of the AA 4 which was designed for use in the MIF and SAmines, the directional elements wure mounted in the cover-plato .

and, since the mine-case is self-orienting, no additional pro-vision was necessary for vertical orientation. In the case of theAA 106 (sometime referred to as A 106), the unit is designedfor use in the BM 1000 H and Bk 1000 L ground mines. When usedin ground mines the directional elements are mounted in a small . %

f float which is moored on a 1 mter length cabel from the mine.The float is released shortly after tho mine reaches thu bottom.The supersonic system is switched on, to save battery power, by a "simple sonic acoustic system of low power consumption. The super-sonic receivers were designed to fire when the target was nearlyoverhead and to discriminato against ships passing abuan,.

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• CONFIDENTIAL ' "

I ~3. KAi 4. ..

N, The A,4 unit was started by SVK (navy) in 1943. Itwas abandoned in 1944-in favor of the Luftwaffe's A1L 106 unitdue to an agreement with the Luftwaffe concerning paralleldevelopments, The IJ4. us nine (,9) magnestostrictive receiverstuned to 25 kc. mounted on the cover plate of an &YI or Sh, mine. ,-'

Of the nine raceiv rs, one was sharply-tuned vertically-directivereceivr4 and-the other eight wore broadly-tuncd receiverswith ,directional characteristic., The receivers wore arranged 0as ,shown in Figure I., with the eight broadly-tunned receiversarranged in a circle around the vertical receiver. The eightcircumferential receivers were designed to opur, t in pairsand the coils of each pair (which were placed diamotrically opposite)were wound in opposite directions? Thus, a sound from overheadwould find the receivers of all four. pairs in phase with eachother with respect to that sound, and the resultant potentialsproduced would mullify each othr., (Figure 1). However. whenthe sound did not originate from ovorhead, a differential potentials(uH)., which ,was used in the circuit for comparison with thepotential produced by the sharply-tuned vurtical receiver wouldappear"

4. Adi 4 Oircuibs.

Several circuits wore experimented with for the L.A 4 unit.

The first one used separate three-stage vacuum-tube amplifiersfor the vertical and horizontal directional systems. Theoutput potentials wore fed to a differentiating relay, and whenthe sound originated from over the mninek it fired. Some diff-iculties were encountered with the use of two parall,l amplifiers, Isince construction of two ,nplifiers with identical characteristicsprove to be difficult. The second circuit used a coimion ariplifierfor the two systems, with a periodic switching as shown in Figure 1 Sto allow both systems altornat use of the wnplifier. The thirdcircuit used a common amplifier, but each systein was connectedto a modulator with a 10 kc, oscillator. Since the resonantfrequency of the receivers was 25 kc., the resultant beat notes ",'.'were 35 kc and 15 kc in each channel, The vertical channel wasthen filtercd to pass 35 kc. only, :nd the horizontal channelfiltered to pass 15 kc only. Thus, the two signal-s were fed to a icommon amplifier, amplified, ru-filtered into two channls,

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CONFIDENTI.

4. AA 4 Circuits.

and finally to the differentiating relay. All three of thesecircuits are shown schematically in Figure 1.

5, AAk 106 - Acoustic Triggering" Circuit.

The acoustic triggering circuit is designed to switch onthe supersonic circuit when ship noises arc detected. It isvery simple, and cinsists of a microphone, transformer, rectifierand relay. The frequencies used are in the 200 - 500 cps range.The acoustic triggering system is so arr-nged in the circuit that

-J continuous acoustic signal is necessary to kujp the supersonicamplifier energized. -.

6. Aji 106.Supersonic Receivers.

The supersonic receivers consist at two nickul magnutostrictivereceivers mounted on top pf a small steel float which is releasedby the mine a short time after reaching the bottom on laying. One 'of the receivers is mounted in a cone and has vertical1 diructivity(trichter schwinger); the other receiver is mounted in a ring aroundthe base of the cone receiver, and has horizontal directivity (ringschwinger). Figure 2 shows the directional characturistics of thetwo receivers. A vortical receiver; B horizontal receiver.

.7. AA 106 - Float and YFloat Release.

Handling and releasing the float for the receivers was thechief difficulty encountered in the development of the AA 106.Several different types of shapes of floats wore exp,rimntedwith, but apparently no satisfactory on9 was developed. The maindifficulty was to keep the float oriented properly when moored ina tideway on a short cable. Difficulty was also encountered inproperly releasing the float from the mine. The float was 'carried

'.4- inside cylindrical open-ended protuctive cover (schutz hube 10),and released a short time after the mine reached tho bottom by 7.the firing of a detonator. The method of mounting of the float

'M on the mine before launching is shown in Figure 3.

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8. ua z 106 xmn. ... '

The -circuit of'the AI 106 unit is shown in Figure 7. Whenthe mine i- laid ifpact ausblg the master switch (3) to closeits arming witch 3-6 ifid break its sh6rt.circuiting contact ., .1-6.- If the tamperature lies between -50 and 3500, thermostaticswitch KTSE'(73) is c166ea d&ndb'b.ttery (2) energized fuse delay

sWitch,,(68). Vhei-(6§)operaites1 with a ,h6rt delay, it bridges2-4 ahd',6-7, -and ,fuse deay swiich ('69) -is energized. When (69)operat6, -40' aid 7-8.Are bi-idged. The floati'-eleasingdstonator is',n6wf'ired Ithiough the aukil-fary contacts of fuse I 0delaf-swit6h'(70) . Detonator-(75)'fired aiid releases the floatWhen switch (70) operates the auxiliary contacts to the float-

\S) release detonator are switched out of the circuit as a precaution. I.,.If the mine is under 15 feet.of'.w~terhydrostatic, switch (74)is open. If, at any time the hydrbstatic pre.ssure falls

'bgeI6W,'l 5 feet clbsure .of'.-(7 )w4 ' l energiie fuse delay switch(7,2),,arid';detonator ( 77) will fire after a delay due to" (72)hr6ugh leads. 25 and -1-5. Ii addition, if -the temperature of the-Widter. 'sh6U1 d g6 ,: e 6 KoSA wil close. '¢ '

Vaft d-5O0, thermostatit switch KTSA wil Closeandiird edetonator '77)i, Sitchihg over of (70) also starts I %cio6ck (63):. This drock is d mechanical clock which derives itsmroti6n fim a dic-nmagnet. balance-whe6l influenced 'by a small' 0 * Jcoil whibh is, einer'gzed in oppoIsite directions as determined bya' -sndia. c6i1i whidh is energized in opposite directions as determinedby a -rversirig: switch, operated,,by 'the balance wheel.- Since one of . -the contacts is normally closed, the clock is solf-starting andruns for the period to which set. Its maximus period is sixtydays. When clock (63) has runoff., -it sitches,.over 'and allowsbattery (1) to energize fuse delay switch (71). At the end of theperiodtof (,7l)'r-iJ-operato and its.multiplo sW1iofis. *".','

• (a) Connect the . side of-the two batteries (1) and (2) <

to the plate, circiiit of' the-amplifier -.tubes.(b) Energizes th6 acoustic triggering circuit by.connect-

-ing battery (67) 'thr6ugh leads 16 and 0 to the -. "',midrophohe (54). ,

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"IN ,ONFIDENTIAL,

9. AA 106 Triggering. --

If an acoustic signal is detected, carbon microphone (54)transforms it into current variations, The variations appearon the secondary of transformer (55) and the signal isrectified Lull-wave by rectifier N5.). The resultant DC Is fedto .eiay B (dl),'which operates wih a short delay due to p.e

condenser (60) Rectifier (59). is not. an efficient rectifier and ; -

acts as an overload by-pass for relay. B remains energized forthe duration of sounds of 200- 500 cps range. Operation of relayB closes its contact (b) which connects battery (67) to theheaters of the seven pehtodes-(5), (Ii), (16), ( 5), (41), (46) Iand(8)

10. A i06 - Amplifier. I. %

Amplifier I consists of pentodes (5), (ll).ahd (16) and theirassociated circuits. The grid of (5) is controlled by the signalreceived by the rin magnetostrictive receiver. The plate circuitis tuned parallel LC circuit to 25 kc.. The ouiput of the thirdstage '-(4 is rectified and fed to a network. Part of this rectified '-potential is fed back to the grids of (5) and (ll) as a regulatingpotential as determined by potentiometer (21) through lead 35. P 0The otential is also divided across resistors (23) and (24) andfed. Thus, the signal strength in'the ring receiver (79) determinesthe sensitivity of Amplifier II to signals -received by the con•receiver (80)"

ll, AA 106 -'nplifier II.

Amplifier II is identical to Amplifier I except that the . .control potential on the grids of its first tow stages is derived '--from the output of Amplifier I instead of its own output.

12. AA 106 - Firing Circuit.

The firing circuit consists of a firing trigger system ..-,including pentode (88) and the actual switching circuit whichincludes relay C. Pentode (88) has its scroen grid and suppressorgrid connected together and, through lead 62, to a tuned LC circuitwith condenser (86) and transformer (85). This circuit is tuned ,

to approximately 1 kc. The control grid potential is normallysuch that the tube cannot oscillate. However, when a sufficiently

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CONFIDENTIAL

12. AA 106 Firing Circuit (Conttd).large signal is received by the cone recei ver and amplifiedat high enough sensitivity of Amplifier II, the grid potential of

(88) is changed and the tube oscillates. The output of (88) isrectified by full-wave rectifier (49) and fed to the operating--..coil of relay A (51) whose sehsitivity is approximately 1 ma. WhenA op.erates, contact (a) closes to lead 30 and connects relay Cin series with thermistor (64) and the battery (2). Presumingfuse delay switch (92) to have opercated during the arming cycle oiC now operates with a delay occasioned by the heating of thethermistor (64). When C operates, its switch cz closes, anddetonator (77) is fired by battery (2) in series with thermistor

13. AA 106 - P.S.E. & Anti-Leak Device.

There is evidence in the circuit of th, same type ofgalvanic P.S.E. and anti-leak device formerly used in the MA 101.In the i±A 101 this took the form of two loops of insulated wireof dissimilar metals wrapped around the switch board with the fusedelay switches. If water entered the unit, a galvanic effect 0resulted between the two wires (Cu and Zn) and relay was actuated.This device appears in the A 106. The cells are shown in thecircuit and indicated.(52). If these cells are activated, they ,2-xenergized relay A (51) in the opposite direction to that producedby rectifier (49). Contact (a) then closes to lead 25 and firesdetonator (77) directly through thermistor (64).

14. AA 106 - Remarks.

The pentodes used in this circuit are all the same type:RV 2, 4 P 45, No other values are known at present. Some of the

test characteristics are known and are shown in Figures 4, 5 & 6. 0

Prepared by:

W. C HOIESC. J.OLENIACZ,i Lieut.., U.S.N.R. Lieut. USNR. @

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