# Sine output between packets **URL:** \ **Category:** GNU Radio\ **Created:** [September 25, 2011, 2:08pm UTC](https://www.ruby-forum.com/t/sine-output-between-packets/212199 "2011-09-25T14:08:27Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\ **Post date:** [September 25, 2011, 2:08pm UTC](https://www.ruby-forum.com/t/sine-output-between-packets/212199/1 "2011-09-25T14:08:27Z")
It seems my old patch that zeroed out the output of the USRP didn’t make it into UHD- we’re seeing a constant sine output between packets- and in our case this messes with the receiver unless we use some custom TX cards that have an amp we can shut down with ATR. Is there any way to fix this? ---
**Author:** ![Brett\_LSTrotter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/df788c/32.png) [@Brett\_LSTrotter](https://www.ruby-forum.com/u/Brett_LSTrotter)\ **Post date:** [September 26, 2011, 5:46pm UTC](https://www.ruby-forum.com/t/sine-output-between-packets/212199/2 "2011-09-26T17:46:32Z")
On 09/26/2011 05:36 AM, Tom R. wrote: > I’ve never noticed this with my work with the UHD. There are various > commands issued to the USRPs to turn it on and shut it off between bursts. > Maybe there’s something missing in the gr-uhd. > > On the other hand, Josh and Nick have been working on using tags with gr-uhd > on the transmit side, which should fix your problem. > > Any comments from the UHD folks? The usrp1 shutdown mechanism in UHD is a little soft (because there is no inline metadata with the samples). However, if you mark end of burst, then the transmitter should get disabled. You can do this w/ tags using this branch: [http://gnuradio.org/cgit/jblum.git/log/?h=mergme/uhd\_tags\_impl\_on\_master](http://gnuradio.org/cgit/jblum.git/log/?h=mergme/uhd_tags_impl_on_master) I would verify that the behavior w/ eob is OK for you on usrp1 by modifying some uhd (non gnuradio) examples before getting into tags. And BTW, I didnt know about this patch. The UHD usrp1 images match the gnuradio ones, so its definitely not in there: [http://gnuradio.org/redmine/projects/gnuradio/repository/revisions/4b5e1238492fe40727d19abefe22ae448c720419](http://gnuradio.org/redmine/projects/gnuradio/repository/revisions/4b5e1238492fe40727d19abefe22ae448c720419) It looks like the patch involves verilog changes. Is this an image that you can just build and drop in place of the existing one or does it need host code support? Have you tried it? -Josh ---
**Author:** ![Brett\_LSTrotter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/df788c/32.png) [@Brett\_LSTrotter](https://www.ruby-forum.com/u/Brett_LSTrotter)\ **Post date:** [September 26, 2011, 5:53pm UTC](https://www.ruby-forum.com/t/sine-output-between-packets/212199/3 "2011-09-26T17:53:21Z")
On Mon, Sep 26, 2011 at 05:36, Tom R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I’ve never noticed this with my work with the UHD. There are various > commands issued to the USRPs to turn it on and shut it off between bursts. > Maybe there’s something missing in the gr-uhd. > On the other hand, Josh and Nick have been working on using tags with gr-uhd > on the transmit side, which should fix your problem. > Any comments from the UHD folks? Brett, if you are using anything beside the BasicTX or LFTX, then it’s also possible you are seeing LO feedthrough/DC offset in the transit mixer, which results in a carrier output between packets. Johnathan ---
**Author:** ![Brett\_LSTrotter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/df788c/32.png) [@Brett\_LSTrotter](https://www.ruby-forum.com/u/Brett_LSTrotter)\ **Post date:** [September 26, 2011, 2:37pm UTC](https://www.ruby-forum.com/t/sine-output-between-packets/212199/4 "2011-09-26T14:37:14Z")
On Sun, Sep 25, 2011 at 8:07 AM, Brett L. Trotter [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)wrote: > It seems my old patch that zeroed out the output of the USRP didn’t make > it into UHD- we’re seeing a constant sine output between packets- and in > our case this messes with the receiver unless we use some custom TX > cards that have an amp we can shut down with ATR. > > Is there any way to fix this? I’ve never noticed this with my work with the UHD. There are various commands issued to the USRPs to turn it on and shut it off between bursts. Maybe there’s something missing in the gr-uhd. On the other hand, Josh and Nick have been working on using tags with gr-uhd on the transmit side, which should fix your problem. Any comments from the UHD folks? Tom