The ARQ-8 System
The ARQ-8 jammer is a good example of rapid response to
a threat. Hastily put together to deal with German glide bomb successes in the
Mediterranean, the R-58/ARQ-8 and T-51/ARQ-8 showed immediate promise in dealing
with the problem. It followed the trend at the time of using a DSBRC approach to widen the
jamming bandwidth, and employed the master oscillator of the transmitter as the LO
for the receiver on the left to ensure locked-in jamming.
It was tuned +/- 2.5MHz about a predetermined center frequency
using the C-93/ARQ-8 control box on the bottom. The "tuning meter" above
the amplifier on the right is a TS-60/U used to measure plate current of the two 4E27 push-pull
amplifier tubes. It was used on virtually all of the jammers as a tuneup tool.
T-51/ARQ-8 transmitter. The oscillator tuning dial on the left reflects the difficulty of tuning up on just the right harmonic!
The power output of the 829-B
PA was about 20 W, but the lack of numerous jamming aircraft to orbit Allied shipping suggested
even more power was required. The AM-33/ART below was the answer to that
need. The broadband characteristic of the output spectrum wasn't amenable to
more conventional amplifier designs, so the designers chose to use a Class B linear amplifier
approach - long before the use by radio amateurs of the technique for SSB.
AM-33/ART Class B linear amplifier and its "in-out" control switch
The AM-33 was essentially identical to the AM-14 linear amplifier,
but had several spare plug-in tuning coils that permitted covering the band of ~30-100MHz.
Of course, the original operational concept for the ARQ-8 involved tuning around for
the German glide bomb control signal, then switching to jamming mode. The C-198/AR in/out
switch below the AM-33 was introduced to enable the amplifier to be controlled more
flexibly. The result is somewhat of a kluge, but with 100W out, a single aircraft at
high altitude could then cover a much greater part of the battle area.
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