Another couple ways to calibrate: I use a GPS receiver with an 10 meg output to calibrate my service monitor.
Before GPS just find out if you have a TV station that is using a Rubidium Standard for their frequency. Here in Milwaukee Ch4 uses one and we always used it to check calibration in the field, the standard was at 67.24 MHz, a lot better than using 10 megs....much higher order of precision. Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Politics is the art of appearing candid and completely open, while concealing as much as possible. -States: The Bene Gesserit View -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Wednesday, December 03, 2003 10:04 PM To: [email protected] Subject: [Repeater-Builder] Re: crystal alignment (how accurate is accurate) Ian, you should have time standard frequencies in Australia on 5 10 and 15 MHz. If you have a secondary receiver, tune in the 10 MHz and compare it to the output of the 10 MHz timebase in your service monitor. This has been one of my obsessions for a while now, to find a way of more accurately setting my 10 MHz timebase in my service monitor. Zero beating with our WWV signal will only get you within a cycle or so. (i.e., one cycle off at 10 MHz equals 40 hertz error at 400 MHz) And then there's trying to find a time when the signal is strong and doesn't fade too much. Since I live about 50 miles south of Ft Collins you would think I would have a strong signal all the time, but no. So I figure there must be a way to use a scope to compare two audio signals (X/Y like we do with PL tones) and be able to set it more accurately. I have tried comparing the 1000 cycle audio tone from an external receiver when I generate a signal from the service monitor I kc off frequency from WWV. Then comparing that to the 1kc tone generated from the monitors own PL tone generator (phase locked to the 10 MHz time bases). You should be able to see a slow drift between the two on the oscilloscope but so far no success, too much noise to see much. Does someone have a way of getting closer than 1 cycle? (no I haven't bought a GPS timebase receiver yet but have drooled over them on Ebay. I've always wondered if a tuned RF receiver using 10 MHz crystals for IF filters would give you a strong 10 MHz carrier that could be used for calibration. Hopefully this is still somewhat on topic since we all need to set our repeaters on frequency. Art - KC7GF Golden, CO Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
