A personal two-way VHF radio communication system featuring modular construction

This paper describes a VHF "personal" communications receiver assembled entirely from individual circuit modules, which are constructed with standard, commercially available, subminiature components. Defective modules can be rapidly replaced, and later repaired or modified. Other receiver features include 1 microvolt sensitivity, double conversion, a crystal filter selectivity package at the high I.F. frequency, and a novel squelch gating circuit. The companion transmitter, more conventional in construction, also is subminiaturized. It features a 1 watt power output, a transistorized modulator, and a DC-DC converter type of power supply with rechargeable nickel cadmium batteries. The shirt pocket size receiver and the transmitter occupy a combined volume of less than 85 cubic inches and together weigh less than 4-1/2 pounds.