I think AM stations have tighter frequency requirements. I think I read some where it was supposed to be + or - 5 hz, of course that is only at 1 to 2 MHz which is still 5ppm stability.
Isnt CDMA supposed to use GPS locked rubidium standards? See i you can find aa control channel in the 800-900 MHz range. On Sun, Sep 6, 2009 at 3:27 PM, <[email protected]> wrote: > At 9/5/2009 21:20, you wrote: >> > OK, now that NTSC video is gone, so are my handy local video >> > carriers that >> > I used to use to check the frequency accuracy of my signal >> > generators. However, I understand that there are pilot >> > carriers buried >> > within the 8VSB DTV signals that can be used for the same purpose. A >> > couple of Google searches revealed that DTV ch. 7 is supposed >> > to have a >> > pilot at 174.310 MHz. Putting my old FM-10 on 174.310 & >> > listening to the >> > beat signal on my R-100, I heard a heterodyne of ~500 Hz. I >> > thought that >> > error was a bit high, so checked a few other DTV pilots (186.310 & >> > 198.310). Interestingly, they were off by the same amount. I >> > moved the >> > FM-10 to 15 MHz & checked it against WWVH; heterodyne was >> > ~1.5 Hz, equating >> > to ~18 Hz @ 180 MHz, not ~500 Hz. My best guess is that the >> > ATSC pilots >> > are actually 309.450 kHz above the bottom of each channel, >> > and the 310 kHz >> > reference is an approximation. >> > >> > Can anyone confirm the above? >> > >> > Bob NO6B >> >>You're trying to make it easier than it is Bob :-) >> >>Normally it would be 309.440559 kHz above the bottom of the channel. That's >>a real big "normally". > > OK, thanks. Well as long as they don't change with the seasons... > > I took a closer look at chs. 7, 9, 11 & 13 today. I see 7 at 174.309450, 9 > at 186.309441, 11 at 198.309730 & 13 at 210.309716. Since the errors > between the frequencies are not linear, I suspect that they're either some > exceptions to the normal freq., or possibly just loose freq. tolerances. > > Bob NO6B > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
