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post #1 of 3 Old 07-03-2014, 11:11 AM - Thread Starter
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Peaking signal frequency

I was wondering if there was a piece of software out there that can be used to find the peak signal frequency. I have a tv capture card going into a linux box and some software will find the frequency at 207000000Hz and others will find it at 207028615Hz. The one at the 2070000000Hz breaks up frequently whereas the one at the 207028...Hz seems to work better.

I've also used rtl-sdr on lower frequencies and a different capture card to be able to visualize the frequency and see the strongest one.

Just trying to see how the best way to find a frequency is with ATSC.

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post #2 of 3 Old 07-03-2014, 12:55 PM
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The ATSC tuner uses the pilot carrier to lock onto the signal so some variance in the exact frequency should not impact reception. I suspect the problem you have is not related to what frequency is being displayed. 207 MHz is just the center of the channel. Maybe the linux box is just using the center frequency and the others calculate the center frequency based on the signal.

Last edited by Calaveras; 07-03-2014 at 01:02 PM.
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post #3 of 3 Old 07-03-2014, 11:42 PM
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From ATSC A/54:

8.5.1 Nominal DTV Pilot Carrier Frequency
The nominal DTV pilot carrier frequency is determined by fitting the DTV spectrum symmetrically into the RF channel. This is obtained by taking the bandwidth of the DTV signal—5,381.1189 kHz (the Nyquist frequency difference or one-half the symbol clock frequency of 10,762.2378 kHz)—and centering it in the 6 MHz TVchannel. Subtracting 5,381.1189 kHz from 6,000 kHz leaves 618.881119 kHz. Half of that is 309.440559 kHz, precisely the standard pilot offset above the lower channel edge. For example, on channel 45 (656–662 MHz), the nominal pilot frequency is 656.309440559 MHz.
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