Experiences with VHF FM-FM radio-telemetry system in the Venezuelan Seismological Network

ABSTRACT

The Venezuelan Seismological Network (RESVAC) has been operating with a VHS FM-FM Radio-Telemtry System for several years. The network which started in 1981, initially with one station, now consists of 21 short-period and 1 long-period station, with 16 of the short-period stations being radio-telemetered. It is essential for seismological studies that high quality data be produced by these stations. Even through the cost of maintenance is high, we have tried to keep it to a minimum. We are applying an analogue frequency modulation radiotelemetry method with low-power carrier in our seismological network. The transmission band is 220-235 MHz. The maximum transmission power is 500 mW. The antennas are Yagi type with horizontal polarization. Our Voltage Control Oscillator sensitivity is 5 V pp imput producing +-125 Hz deviation in the sub-carrier.