AW: Help_USRP FM receiver unsuccessfull

[Thangaraj Mukara Dhakshinamoorthy]

Hello Gary,

1. First of all, thanks for your help. The Problem was with RF Settings: AGC 
should be disabled and Antenna Rx2 Should be selected instead of Tx/Rx! After 
these corrections I was able to listen to FM clearly without any trouble! 
Anyhow, I will try out your suggestions too!

2. Currently I am having GNU radio 3.8.1.0, but there are some grc blocks 
missing such as soapy or RTL-SDR which I also need to program RTL-SDR Dongle, 
therefore I would like to upgrade the GNU-Radio to newer version. Which version 
would you suggest? And what is the simple way to achieve it without going 
through difficult steps?

My system config:
OS: Ubuntu 20.04.3 LTS
OS Type: 64-bit
RAM: 3.8 GB
Processor: Intel Core i5-2450M CPU @2.50GHz x4
UHD version: 3.15.0.0
GNU Radio version: 3.8.1.0
SDR Device: Ettus USRP N320

Looking forward to your kind response :)

PS: Thanks to Barry Duggan as well!

Regards,
Thangz :)



-----Ursprüngliche Nachricht-----
Von: Discuss-gnuradio <discuss-gnuradio-bounces+thangaraj=komro.net@gnu.org> Im 
Auftrag von Gary Schafer
Gesendet: Freitag, 15. Oktober 2021 01:08
An: discuss-gnuradio@gnu.org
Betreff: Help_USRP FM receiver unsuccessfull

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