# RX channel 1 out of range for configured RX frontends **URL:** \ **Category:** GNU Radio\ **Created:** [November 3, 2014, 11:56pm UTC](https://www.ruby-forum.com/t/rx-channel-1-out-of-range-for-configured-rx-frontends/232904 "2014-11-03T23:56:44Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [November 3, 2014, 11:56pm UTC](https://www.ruby-forum.com/t/rx-channel-1-out-of-range-for-configured-rx-frontends/232904/1 "2014-11-03T23:56:44Z")
Hello, ``` We are using a TVRX2 board with a N200 USRP. Until recently, the ``` system was working properly with two channels using the attached flowgraph. For reasons that are unclear, it stopped working and is no longer capable of two channel operation (if we set the Num channels parameter to 1, the system works, but with only one channel). So far as we can tell, nothing in the S/W changed. Version details and the error message appears below. Suggestions what has gone wrong would be most appreciated. –Dan H/W: Dell Optiplex Dual 2.4 GHz, 2 GB / USRP N200 with TVRX2 GPSDO boards. OS: Ubuntu 14 gnuradio: 3.7.6 Traceback (most recent call last): File “/home/marlow/gnuradio/TVRX2/top\_block.py”, line 177, in tb = top\_block() File “/home/marlow/gnuradio/TVRX2/top\_block.py”, line 94, in **init** channels=range(2), File “/usr/local/lib/python2.7/dist-packages/gnuradio/uhd/ **init**.py”, line 122, in constructor\_interceptor return old\_constructor(\*args) File “/usr/local/lib/python2.7/dist-packages/gnuradio/uhd/uhd\_swig.py”, line 1753, in make return \_uhd\_swig.usrp\_source\_make(\*args) RuntimeError: LookupError: IndexError: multi\_usrp: RX channel 1 out of range for configured RX frontends [http://www.hep.princeton.edu/~marlow/gnuradio/TVRX2.png](http://www.hep.princeton.edu/~marlow/gnuradio/TVRX2.png) [http://www.hep.princeton.edu/~marlow/gnuradio/TVRX2.grc](http://www.hep.princeton.edu/~marlow/gnuradio/TVRX2.grc) ---
**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\ **Post date:** [November 4, 2014, 12:02am UTC](https://www.ruby-forum.com/t/rx-channel-1-out-of-range-for-configured-rx-frontends/232904/2 "2014-11-04T00:02:06Z")
On 11/03/2014 05:55 PM, Daniel M. wrote: > Version details and the error message appears below. Suggestions > what has gone wrong would be most appreciated. > > –Dan > There’s a fix for this problem in the most recent “master” of GR, which > doesn’t appear in the “maint” branch. It was a wee problem in gr-uhd that was introduced by wanting to be more “strict” about master-clock LOCK, and, well, that provoked other underlying problems. What are you using the TVRX2 for, BTW. I’ll note that it has cannot-be-defeated hardware AGC, so it’s of only limited utility for radio astronomy, which I think you’re probably using it for… 🙂 ---
**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\ **Post date:** [November 4, 2014, 12:16am UTC](https://www.ruby-forum.com/t/rx-channel-1-out-of-range-for-configured-rx-frontends/232904/3 "2014-11-04T00:16:26Z")
On Nov 3, 2014, at 5:59 PM, Marcus D. Leech wrote: > There’s a fix for this problem in the most recent “master” of GR, which doesn’t > appear in the “maint” branch. > > It was a wee problem in gr-uhd that was introduced by wanting to be more > “strict” about master-clock LOCK, and, well, that provoked > other underlying problems. > > What are you using the TVRX2 for, BTW. I’ll note that it has cannot-be-defeated > hardware AGC, so it’s of only limited utility for > radio astronomy, which I think you’re probably using it for… 🙂 Hi Marcus, Thanks. Does that mean we need a new install of GR? The one we have is quite recent. Regarding the TVRX2, I did not know about the AGC issue. We are using it for RA (pulsar searches). Since we are doing synchronous detection, it’s not clear to me that the AGC will be a fundamental problem, since we don’t need quantitative power measurements. We wanted two channels since we are using crossed Yagi’s. I don’t see any alternatives from Ettus. –Dan ---
**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\ **Post date:** [November 4, 2014, 12:20am UTC](https://www.ruby-forum.com/t/rx-channel-1-out-of-range-for-configured-rx-frontends/232904/4 "2014-11-04T00:20:36Z")
On 11/03/2014 06:15 PM, Daniel M. wrote: > Hi Marcus, > > Thanks. Does that mean we need a new install of GR? The one > we have is quite recent. > build-gnuradio by default installs the “maint” branch–since that is, > generally, more likely to be somewhat-more-stable. If you use the -m > option to > build-gnuradio, it’ll fetch “master”. This fix is quite recent. > Regarding the TVRX2, I did not know about the AGC issue. We are > using it for RA (pulsar searches). Since we are doing synchronous > detection, it’s not clear to me that the AGC will be a fundamental > problem, since we don’t need quantitative power measurements. We > wanted two channels since we are using crossed Yagi’s. I don’t see > any alternatives from Ettus. In terms of multi-channel daughtercards for N2xx/USRP1/X3xx/E1xx, yeah, the TVRX2 is it. But the B210 is dual-channel, strictly-coherent (they share the same LO). Ken Tapping and I have been doing C-band correlation interferometry with one.