Thank you Ian Wells ----- Original Message ----- From: "Mike Morris WA6ILQ" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, December 04, 2003 6:25 PM Subject: Re: [Repeater-Builder] Re: crystal alignment (how accurate is accurate)
> 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/ > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
