Tom, I can send you the schematic and artwork for the VCO that I designed that was used in the 55 USGS telemetry stations in New Madrid, the Aleutian network, as well as in Greece and Soviet Asia. At one time Sprengnether was producing it for us as part of the micropower Amp/VCO telemetry cannister. It is a micropower system (power about 0.5ma at +.- 4.05 volts) with active temperature compensation with the standard IRIG frequencies of 420, 680, 1020, 1360, 1700, 2040, 2720, 3060, and 3400 hz. It uses the VCO section of the micropower CD4046, and LM4250 op-amps. The output is a sine derived by an 8-step summation. Unfortunately the design is pre-web, and nothing has been scanned. The DC-DC converter design was published in BSSA long ago. "A 50-Milliwatt Power Converter to Replace Mercury Batteries in Seismic Amplifier/VCO Systems", Bull. Seism. Soc. Am., 72, ....... The whole telemetry cannister (same dia. but 3x as long as an L4-C seis) operates on 4 ma at 13 volts from the VHF transmitter battery. Some are still in use. If you send me an address, I can mail the info. If you only want one board, I can probably send you a blank ready to load. Regards, Sean-Thomas __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>