Re: [Discuss-gnuradio] GRC + USRP2 + WBFM: synchronization problem?

[Ed Criscuolo]

Looks like you have your interpolator and your multiply blocks switched.

The way you have it, the L-R audio is interpolated up to a 200k
sample rate, and then multiplied with a 19khz subcarrier at
a 44.1k sample rate.

Do the multiply first, then interpolate the product.

Or alternately,  simply change the 19 kHz sample rate to 200k.

@(^.^)@  Ed


On 3/28/11 3:23 PM, Marcin Szelest wrote:
> Hello,
>
> I have created FM transmitter in GRC:
> http://szelest.org/question/TX_RX.grc.png
>
> Unfortunately demodulated audio has poor quality and annoying
> distortions. I have spent a lot of time on it without positive effect.
> Here is how demodulated audio sounds like:
> http://szelest.org/question/recorded.wav
>
> When I have created FM receiver in GRC (bottom part of the schematic),
> demodulated audio sounds perfectly on my PC.
> Any ideas?
>
> I'm using gnuradio3.3.0 + USRP2(with interpolation changed from 4 to
> 2) + BasicTX + FT857D as hardware receiver.
> GRC file: http://szelest.org/question/TX_RX.grc
> input WAV: http://szelest.org/question/indiana.wav
>
> Regards,
> Marcin SQ9DJJ
>
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