# USRP1 Rev 4.3 Benchmark\_tx/rx transmit/receive issue **URL:** \ **Category:** GNU Radio\ **Created:** [April 2, 2010, 10:55pm UTC](https://www.ruby-forum.com/t/usrp1-rev-4-3-benchmark-tx-rx-transmit-receive-issue/186248 "2010-04-02T22:55:52Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Phillip\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e274bd/32.png) [@Phillip\_W](https://www.ruby-forum.com/u/Phillip_W)\ **Post date:** [April 2, 2010, 10:55pm UTC](https://www.ruby-forum.com/t/usrp1-rev-4-3-benchmark-tx-rx-transmit-receive-issue/186248/1 "2010-04-02T22:55:52Z")
I am absolutely stumped, any help with this would again be greatly appreciated. Last week I had a question trying to get USRP2 to work in my MAC testbed. I decided not to worry about that for the time being and borrowed 2 USRP1s from another research group to finish a project. However, I am not unable to get benchmark\_tx/rx.py or obviously tunnel.py to work with these USRPs as I have hundreds of times before with the other USRPs. My first 2 USRP1 are Rev 4.5. I have 4 RFX2400 Rev 30, tested all successfully on 4.5. USRP1s in question are Rev 4.3. GNU Radio 3.3.2 The Rev 4.3 transmits a waveform that appears on rev 4.5 FFT as a good gmsk (tried dbpsk also) signal. I set the TX amplitude to 5000 and RX gain to 30, but have tried many many values. The rev 4.3 will not successfully decode the rev 4.5 signal either. Literally when I swap the USRPs out with the exact same set up, it works with rev 4.5 boxes. I have tested the usrp 4.3s including FFT, siggen, etc. and everything else seems fine other than packet decode and correct transmitting. I also tried RFX900’s between those two with no avail. I’ve tried all the parameters I could think. Do I need to use a specific older GR revision? Special decimation, interpolation, samples/symbol, etc? As a side note: the simple reliable MAC I have implemented which includes RTS/CTS (w/ threshold), ACK, multi-hop, multiframe transmit is working great (so far). I look forward to publishing it for the community when I finish this project. Regards, Phil Walsh Auburn University ---
**Author:** ![Phillip\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e274bd/32.png) [@Phillip\_W](https://www.ruby-forum.com/u/Phillip_W)\ **Post date:** [April 3, 2010, 3:12am UTC](https://www.ruby-forum.com/t/usrp1-rev-4-3-benchmark-tx-rx-transmit-receive-issue/186248/2 "2010-04-03T03:12:50Z")
Solved it: Installed an old version, GnuRadio 3.1.1, I had on disk and the rev 4.3 USRP1s seem to work fine now on that. Is this a known/common issue? ---
**Author:** ![Phillip\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e274bd/32.png) [@Phillip\_W](https://www.ruby-forum.com/u/Phillip_W)\ **Post date:** [April 3, 2010, 3:15pm UTC](https://www.ruby-forum.com/t/usrp1-rev-4-3-benchmark-tx-rx-transmit-receive-issue/186248/3 "2010-04-03T15:15:00Z")
On Apr 2, 2010, at 9:08 PM, Phillip W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I am absolutely stumped, any help with this would again be greatly > I have 4 RFX2400 Rev 30, tested all successfully on 4.5. > FFT, siggen, etc. and everything else seems fine other than packet > community when I finish this project. > > Regards, > > Phil Walsh > Auburn University It’s likely that the new USRPs you’re using have frequencies that are too far apart from each other. This is a particular problem with the higher frequency boards. Using usrp\_fft.py, try to see what the frequency offset is and compensate for it to some degree. The older version of GNU Radio you got working I think did the acquisition slightly differently and was able to handle the larger frequency offset. The new v2 code for the digital modulations in the Git tree should correct this, too. Tom ---
**Author:** ![Phillip\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e274bd/32.png) [@Phillip\_W](https://www.ruby-forum.com/u/Phillip_W)\ **Post date:** [April 3, 2010, 6:34pm UTC](https://www.ruby-forum.com/t/usrp1-rev-4-3-benchmark-tx-rx-transmit-receive-issue/186248/4 "2010-04-03T18:34:01Z")
> The new v2 code for the digital modulations in the Git tree should correct > this, too. > > Tom Thanks Tom! That definitely sounds like it could be the problem. I will see if I can solve it with a frequency offset. Also a correction to my solution, it wasn’t GR 3.1.1 I got to work with it. It was the svn revision 8586. Just in case someone looks into it further. Phil