I was in a test with ‘usrp2_fft.py’ code in the gr-utils directory and
that the program is not running as I expected in certain conditions.
I was watching signals running the usrp2 as a spectrum analyzer with the
Test environment information
- usrp2 + gnuradio 3.2.1 (or gnuradio 3.2.2)
- usrp2 H/W version : rev. 3
- usrp2 SD card image/code version : Cannot identify
- RF RX Interface : basic RX board
- Host PC O/S : ubuntu 9.04 Desktop (64bit version)
- When I set the decimation rate to ‘20’, and open the RF input
port(hooked up no signals), the noise level goes down to -380dBm and and
flat. With the decimation rate of 18 or 22, it looks O.K. Noise level is
around -90dBm and I can see the frequency domain envelope of white
- At that moment, the samples coming from usrp2 are all zero. I
confirmed it with wireshark.
- I figured out that it happens not only with the decimation rate of
but with 40, 60, etc.
I was suspicous if it went like that with multiples of 20, but it
happened with 50, 82, etc.
- When I feed signal to the RF RX port, it goes back to normal. So,
can say that it happens when the input signal level(power) is lower that
certain level. However, it does not happen with other decimation rates
4, 6, or 18.
I would like to know
- If this is a known issue. In that case, I also would like to know if
there is any workaround.
- If this is a new issue, I would like to ask experts in this mailing
to reproduce the experiment and let me know why this happens and what I