|
The AA 4 unit
was started by SVK in 1943. It was abandoned in 1944 in favor of the
Luftwaffe's AA 106 unit as a result of an agreement with the Luftwaffe
concerning paral-lel developments. The AA 4 used nine magneto strictive
receivers tuned to 25 kc. moun-ted on the cover plate of an EMF or SMA mine.
Of the nine receivers, one was a sharply-tuned vertically-directive
receiver, and the other eight were broadly-tuned receivers with a
directional characteristic. The receivers were arranged as shown in
figure 222, with the eight broadly-tuned receivers
arranged in a circle around the vertical receiver. The eight circumferential
receivers were designed to operate in pairs, and the coils of each pair
(which were placed diametrically opposite) were wound in opposite
directions. Thus, a sound from overhead would find the receivers of all four
pairs in phase with each other with respect to that sound, and the resultant
potentials produced would nullify each other. However, when the sound did
not originate from overhead, a differential po-tentials (Uh),
which was used in the circuit for comparison with the potential produced by
the sharply-tuned vertical receiver would appear. |
