Pulsed, coherent low power VHF/UHF transmitters-of minimal component count and weight

Abstract

The parameters that directly influence the design of stable, coherent and pulsed VHF/UHF sources are identified. Assuming currently available commercial technology, an attempt is made to identify the optimum frequency, for maximum range, at which systems used for animal tracking should operate. The current state of the art of pulsed VHF/UHF transmitters, using quartz crystal resonators of minimum weight and volume is reviewed together with measurements on simple oscillator and frequency multiplier circuitry. Commercial chemically etched fundamental and overtone quartz crystal oscillators in the VHF frequency band have only recently become available; the performance of these units is compared with that available from low-ESR (effective series resistance) quartz crystal oscillators operating at third overtone in the 60-100-MHz region and with frequency multiplication factors of 3-8. Areas are identified where further research and development are required.<>