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Help_USRP FM receiver unsuccessfull
From: |
Gary Schafer |
Subject: |
Help_USRP FM receiver unsuccessfull |
Date: |
Thu, 14 Oct 2021 19:08:03 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 |
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