Help_USRP FM receiver unsuccessfull

[Gary Schafer]

Thangaraj,

The first thought for your "aU" situation is that your sample rates don't match between your USRP and the audio card on your 
computer. The "a" part of "aU" means the audio card is not getting enough samples. If you run your Gnu Radio graph, is 
there a line above all of the "aU"s that says something like, "[WARNING] [MULTI_USRP] The hardware does not support the 
requested RX sample rate:", followed by a couple of lines that say something like, "Target sample rate: 1.920000 MSps, Actual 
sample rate: 1.923077 MSps"? If so, then your USRP is not able to *exactly* set the sample rate to 1.92 MHz.

If you are *not* able to set the sample rate of the USRP to precisely 1.92 MHz, 
try the following changes to your graph (which looks correct from your image):

Sample rate: 2e6 (2 MHz)

Rational Resampler Block:
- Interpolation: 24
- Decimation: 250

Leave all of the other blocks the same.

Long story short: If I'm correct, it's because the USRPs can only pick from a 
small number of sample rates. For the N320, they start with one of three sample 
rates (200 MHz, 245.76 MHz, and 250 MHz), then they decimate. The sample rate 
*must* be one of these values after decimation. Otherwise, the USRP will pick 
something close. And close is not good enough for our purposes. The above 
information came from the Ettus website at https://kb.ettus.com/N320/N321. If 
I'm reading it correctly, it *should* be able to set the sample rate of the 
N320 to precisely 1.92 MHz. Again, assuming I'm reading it correctly.

Finally, I agree completely with Barry that your antenna should be more than 
adequate for the USRP. Best of luck, and please let us know if you're able to 
solve this problem.

Regards,

Gary