Hi To complete the thought:
Three base stations on three different transmit frequencies over a 50 MHz range. Mobile has a local oscillator at say 200 MHz. Filter the incoming frequency range, stuff it into a mixer, filter the output. What's transmitted back gets processed at the base station. Yes you would have to be running at a high enough frequency to keep everything in an appropriate band. Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of johncr...@aol.com Sent: Friday, February 01, 2013 12:16 PM To: time-nuts@febo.com Subject: Re: [time-nuts] question for expert time guys (Hal Murray) Hello Hal - I spent a lot of my RF engineering career in related areas, including radar, EW, and spread spectrum timing systems. Since the distance is short and the cost is an issue you may wish to consider an analog system solution. Specifically your master station transmits a RF signal that is FM modulated with a high frequency tone. The remote unit is a transponder. It receives the tone and re-transmits back on another frequency. Almost no parts required. At the master station the phases of the outgoing and returning tones are compared. The distance is directly proportional to the phase shift between the outgoing and incoming tones. For instance if the tone is 10 MHz the 360 degrees of phase is 100 nS which is about 100 ft round trip. The phase may be measured either analog and A/D converted or digitally and in either case is then easily converted to range by your processor. By adjusting the tone frequency you can set the full scale range. To increase resolution higher frequency tones may be used. To overcome ambiguity when the range goes beyond 360 degrees of phase, add a lower frequency tone to resolve the ambiguity. This scheme has been used in surveying instruments (the Teleurometer) and even an ill fated German bombing system in WWI. The latter proved delightfully easy to jam since the Brits had a spare TV transmitter in the correct band. Look up something like "tone ranging". -john c roos k6iql _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
