If you are looking at the 3.58 MHz on demodulated video, then you are looking at a framesync. In today's world of broadcasting, the consumer TV's will be much more forgiving of the 3.58 drift and still lock on to it, so its accuracy is not as important as it was back in the day. Knowing what I do about the TV station I work for, I would NOT use that as a reference. I don't think I have ever checked our 3.58 for accuracy. The FCC is MUCH more relaxed about TV standards than they were 20 years ago. If you have a 'top notch' station with a rubidium or GPS based frequency standard, then using the carrier (not demodulated 3.58 video) will get you a good reference. --John
----- Original Message ----- From: "Gregg Lengling" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, December 04, 2003 7:02 AM Subject: RE: [Repeater-Builder] Re: crystal alignment (how accurate is accurate) > Not using the frame syncs....using the actual RF carrier! > > 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: Rod Lane [mailto:[EMAIL PROTECTED] > Sent: Wednesday, December 03, 2003 10:55 PM > To: [email protected] > Subject: RE: [Repeater-Builder] Re: crystal alignment (how accurate is > accurate) > > Used to be... In the good old days before frame syncs, you could wait > until the local affiliate was in network programming and you had a REAL > good 3.58 reference. Not so anymore. 3.579545 was an easy number to > remember for some reason... ;^) > > 73 de N1FNE > ----- Original Message ----- From: "Steve S. Bosshard (NU5D)" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, December 04, 2003 1:16 AM Subject: RE: [Repeater-Builder] Re: crystal alignment (how accurate is accurate) > I remember an old QST article about the 3.58 Mhz color burst sig on network > tv being tracable to NBS. If I remember correctly the sets are phase locked > to the incoming sig? > > Never was much at TV.. > -----Original Message----- > From: Gregg Lengling [mailto:[EMAIL PROTECTED] > Sent: Wednesday, December 03, 2003 11:07 PM > To: [email protected] > Subject: RE: [Repeater-Builder] Re: crystal alignment (how accurate is > accurate) > > 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/ > > > > > > > > > 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/ > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
