The German V2 jammer


The three primary transmitter units - power oscillator, modulator, and audio oscillator

In 1944 the threat of the German "Victory weapons" caused a great deal of activity in electronic countermeasures work. Initial signals collection around Peenemunde showed some unusual emanations in the 20-70MHz area, and it was surmised that the V2 was guided by this frequency. Subsequent analysis could detect nothing in that band of frequencies when the weapons began falling on London and the English countryside, further deepening the mystery. As it turned out, postwar accounts indicated that one of the initial guidance systems was comprised of a set of "searchlight" beams that were directed upward from a circle of transmitters around a V2 launch site, and this was allegedly used to guide the missle in the first 60 seconds or so of its flight, after which it was guided by an on-board gyro and then became a straight ballistic package. At any rate, the British began deploying a ground based jammer with about 75KW output to counter the perceived threat, and used highly directional antennas to point toward Peenemunde. Ever the practical ones, the Americans were concerned about what happened if the V2 show went on the road...the Germans had proved masters of mobile weaponry. In any event, the ARQ-11 was a jammer that was quickly built and tested in a B-24 during the summer of 1944. It used a pair of British "micropup" radar pulse triodes in a push pull power oscillator configuration to get 1,700 watts output at the lowest frequency point. The need to get such power out of tubes designed for pulse applications required a huge "canister vacuum cleaner" blower at the rear of each tube, simply to obtain any life out the tubes at all.


One of the REL-1 micropup tubes

The power oscillator was a tuned push-pull oscillator with no further amplification, pictured below. Note the plate current meter,which reads the combined plate current from the 6kV supplies - 3 amperes full scale!


T-102/ARQ-11 power oscillator

It's probably a miracle that this set has survived - it has numerous parts in it that radio amateurs used after the war to make kilowatt rigs. Below are shown some details of its exquisite construction.




This view shows the plate coils and swinging link. Five sets of these coils were required to cover 20-70MHz.



The modulator is designed to provide the proper grid excitation for the three modes of operation shown on the transmitter panel, and included a clipper stage, a 3MHz local oscillator, a full wave rectifier, an output keying stage, and a power supply. The 30Hz to 30,000Hz sine wave oscillator input coming from the O-28/ARQ-11 is amplified and shaped to a square wave, which is used to key the local oscillator. The output of that stage (a pair of 807 tetrodes) is rectified and applied to the grids of the main 811 modulator tubes.


MD-42/ARQ-11 modulator


O-28/ARQ-11 audio oscillator

Three power supplies were used with three phase 400~ input to get the 6kV at 2 amperes needed for the transmitter. Only about a dozen complete ARQ-11 sets were manufactured before the contract was terminated because of the pace of ground advance in Europe. This particular power oscillator is serial number 9, the modulator is serial number 6, and the audio oscillator is serial number 5. This set is missing only the C-187/ARQ-11 junction box/power panel and the associated R-21/ARQ-11 receiver.


The three PP-130 power supplies

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