Re: [Discuss-gnuradio] Question about sampling

[Dinkar Bhat]

Thanks for the info. One of my issues is the detection of the pilot frequency
(which is a specific frequency relative to the channel). Now, using FFT on the samples
that I captured using the ADC, I geta  certain frequency resolution (bin size) that is inversely
proportional to the the length of the ADC. But I might miss the pilot and hence I was wondering
if I should sample at much higher rate than 2* max frequency. Even then I might miss
the pilot, and I am wondering what is approach?

Dinkar

cswiger wrote:

On Wed, 16 Mar 2005, Dinkar Bhat wrote:

  

I joined this group recently and have learnt a lot.
    

Join the crowd (that are learning a lot)

  

I had a rather
fundamental question. Suppose I sample the
IF output (say, centered at 40 Mhz) of a tuner/mixer tuned to a ATSC DTV
channel (6Mhz wide), and I want to detect the
pilot frequency which is added to the channel during transmission, would
I have to sample the IF
at much higher than 2*Nyquist fy? The reason I ask is that the pilot
    

If the IF is bandlimited (say 40 +- 4Mhz) you can sample at a much lower
rate using 'bandpass sampling', use a slower ADC and get fy translation
at the same time. For example, a tuner we use is centered at 36Mhz, our
ADC samples at 64Mhz ( < 2* IF ) but the IF appears to be at 28Mhz
( 32 - ( IF - 32 )).

--Chuck