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VT引信可被干扰，但不是被动感应，而要主动发射电波诱发。
延伸阅读：
Electronic countermeasures
A move to develop countermeasures against proximity fuzes stemmed from the Germans, who during the "Battle of the Bulge," captured an Army munitions dump that contained a large number of the new radar proximity-fused shells. Concerned that the Germans might attempt to copy the proximity fuze, the Research Division of the Aircraft Radio Laboratory at Wright Field, along with the help of the RLL, was called in begin the development of jamming equipment. Lieutenant Jack Bowers, an engineer with the Aircraft Radio Laboratory at Wright Field, recounted the following to Alfred Price:
"The proximity fuse had been a closely guarded secret on our side. Even though we had been working on countermeasures for a long time, we at Wright Field had never heard of the device. Now we were asked to investigate, on a crash basis, the possibility of a jammer to counter the fuse. We asked why such a jammer had not been developed earlier, and were told that the developing agency had conducted tests and concluded that the fuse could not be jammed! We worked on the problem, and within two weeks, a jammer had been built which would detonate the proximity fuses prematurely."
Since the body of the shell served as the antenna for the radar proximity fuse, it limited the frequency spread of the transceiver from 180 to 220 MHz. The APT-4, a high powered jammer, already covered that part of the spectrum. A motor-driven tuner was added to sweep the jamming transmitter’s signal up and down the band theoretically covered by the fuze. Several modified APT-4’s were installed in a B-17, and a top priority full scale test was arranged at Eglin to see whether the countermeasures would be effective.
Price, in another interview with Lieutenant Ingwald Haugen, one of people involved with the test, Haugen tells him:
"For the firing test, the Army sent a battery of 90 mm anti-aircraft guns. These were emplaced near Eglin. We had requested that during the test the guns would fire VT (proximity fused) shells with spotting charges, so that when the fuses operated, the shells would burst with only a puff of smoke. We were told this was not possible. The VT fuse was about 1 1/2 inches longer than the normal mechanical fuse and it would not fit in a shell carrying a spotting charge. So, we were going to have to use live high explosive VT fused shells for the test. As a safety measure, the guns were to be offset by a small angle, initially 30 mils (about 1.7 degrees), later decreased to 12 mils (about .6 Degrees)."
"It was the sort of test that would never be allowed today under the prevailing flight safety guidelines. At the time, however, there was a war on, and the small risk to our one aircraft had to be weighed against the far larger risk to our whole bomber force if the Germans used such a weapon against us. We who were to fly the test were confident we would be all right - we hoped that the jamming would work as planned, and if it didn’t, the offset fed into the guns would burst the shells at least 240 feet away from us at a range of about 20,000 feet."
"The test lasted about 3 months, during which about 1,600 VT shells were fired, individually, in our direction. Sitting in the fuselage of the B-17, the two RCM operators could pick up the radar transmissions from the shells coming up. The VT fuse radiated CW (continuous wave) signals, but the projectiles would often yaw a little in flight. This, in combination with the spin of the shell, would modulate the signal. We in the back could not see out, but the pilots and the navigator would get a kick out of watching the shells burst well below, or if there was a late burst because the jamming had taken some time to sweep through the shell’s frequency, it might explode close to our altitude. The general conclusion of the test was that, modified to radiate CW swept across the VT fuse band, the APT-4 jamming could significantly reduce the effectiveness of the proximity fused AA shell."
Extracts from The Radio Proximity Fuze - A survey, By Edward A. Sharpe Archivist, SMEC (c) (now SMECC c.2003) |
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发表于 2015-4-24 12:55
发表于 2015-4-24 17:23
