Operation of the fuze occurs when the output signal from the amplifier reaches the required amplitude to fire the thyratron. Selective amplification of the low-frequency signal is generally necessary. The low-frequency signal can be used to trigger an electronic switch. The interference it creates with the transmitter results in a low-frequency beat caused by the combination of the transmitted and the reflected frequencies. The frequency of the reflected wave differs from that of the transmitted wave, because of the relative velocity of the fuze and the target. In a doppler-type fuze, the actuating signal is produced by the wave reflected from a target moving with respect to the fuze. When this stage of development was reached, work on photoelectric fuzes was terminated (October 1943), and the radio method was prosecuted even more vigorously than before.Īmong various possible types of radio proximity fuzes, an active-type fuzed operating on the doppler effect was selected as being the most promising method. The two methods were pursued in parallel until it was definitely established that radio proximity fuzes could be produced to fulfill all requirements. The radio method appeared to be more complicated, but it afforded opportunity for reliable performance not only 24 hours a day but under a much wider variety of other conditions than were possible with the photoelectric fuze. The photoelectric method was selected because it appeared a relatively easy approach to the proximity fuze problem, although the fuzes would be limited to daytime use, unless light sources were provided. Following initial exploratory investigations, two types of fuzes, optical (photoelectric) and radio, were selected for intensive development. The former was necessary to insure performance under various stringent Service conditions, and the latter, to allow the fuze to be contained in a small volume and to be produced quickly in large quantities. Prime considerations for a proximity fuze were reliability and simplicity. Various methods of obtaining proximity operation against a target were investigated: electrostatic, acoustic, optical, and radio. Proximity fuzes are intended to detonate missiles automatically upon approach to a target and at such a position along the flight path of the missile as to inflict maximum damage to the target. Radio Proximity (VT) Fuzes and How They Operate
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