At 11:03 PM 12/3/03 -0500, you wrote: >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
One technique that I overheard a local NBC engineer discussing was that he took advantage of the fact that the TV transmitter video carrier was phase-locked to a rubidium standard. He first zero-beated 10mhz WWV with his service monitor then switched over to the video carrier of the TV station and fine tweaked the service monitor's time base. If you know any local TV engineers it would be worth asking if any have rubidium- locked transmitters. Just an idea that I overheard, I haven't tried it. Or measure the color burst crystal in a TV set - it has to be dead-on to 3.579-something-or-other mhz or the colors shift. Mike WA6ILQ Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
