I’m currently testing UHD.
I use two USRPs with one SBX on each.
and I got GNU Radio 3.5.0rc0 on Ubuntu 10.10 and benchmark programs
When I run benchmark_tx/rx.py, however,
tx@ubuntu $ ./benchmark_tx.py -f 410M
rx@ubuntu $ ./benchmark_rx.py -f 410M
I can see ‘dots’ representing a signal is transmitted on a transmitter
but a receiver does give nothing on a screen.
and the screens on the both side, I got this message.
No gain specified.
Setting gain to 5.750000 (from [-20.000000, 31.500000])
The hardware does not support the requested TX/RX sample rate:
Target sample rate: 0.050000 MSps
Actual sample rate: 0.250000 MSps
Symbol Rate: 25000.000000
Requested sps: 2.000000
Given sample rate: 250000.000000
Actual sps for rate: 10.000000
Requested sample rate: 50000.000000
Actual sample rate: 250000.000000
What did I do wrong?
- Wrong frequency option (either tx or rx)
- Wrong/Unspecified sample rate option (either tx or rx)
- Too weak signal strength to catch
Seokseong Jeon,PhD Candidate
Communication & Networks Lab
IT Convergence Engineering (ITCE), POSTECH, Korea
+82 10 8338 1229,gee.songsong at gmail . com
On Sun, Nov 20, 2011 at 1:57 AM, Songsong G.
Thank you for all of you.
I’ve got some progress on it.
From Tom’s suggestion I give options to benchmark_tx.py
$ ./benchmark_tx.py -f 450e6 --tx-amplitude=0.02 --tx-gain 30 -S 10
And looking its spectrum,
I could get a distinct frequency component around 450 MHz.
After that, I ran benchmark_rx.py
$ benchmark_rx.py -f 450e6 --rx-gain=50 -S 10
(I modified receive_path.py to have threshold with -80 dB to filter out
And I got a following result.
This means that I did wrong in either trasmitting or receiving.
- Still signal is clipped (but, I guess not, --tx-amplitude=0.02)
- Threshold value is mistaken (threshold = -80 [dB])
- sample per symbol (-S 10)
- –tx-gain, --rx-gain might be wrong.
- or something I am missing.
Please give your suggestions. I am almost close to the goal.
And thank you for all of you in advance
Yes, you are close. It’s probably a matter of tweaking the receiver gain
and the transmit power to the right levels. We have a digital AGC, but
doesn’t do much for the important analog gain stages you need to get the
It could also be a frequency offset, although your graph showed that the
signal looks pretty well centered. It be good to zoom in, though, or use
the uhd_siggen to transmit just a tone and find out how far off