# USRP LO Relocation Latency **URL:** \ **Category:** GNU Radio\ **Created:** [September 26, 2012, 7:01pm UTC](https://www.ruby-forum.com/t/usrp-lo-relocation-latency/223245 "2012-09-26T19:01:36Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\ **Post date:** [September 26, 2012, 7:01pm UTC](https://www.ruby-forum.com/t/usrp-lo-relocation-latency/223245/1 "2012-09-26T19:01:36Z")
Dear gr / USRP fellows, I’m currently experimenting with USRP B100 Local Oscillator relocation time. I’ve done some experiments on the RX path by tuning towards and away from an OFDM beacon signal. I have flushed into the received signal some recognizable “relocation marks” which allowed me to analyze the received signal integrity in the temporal vicinity of the relocation instant. It looks like the LO responds to the steering command in some milliseconds to about two tens of millisecs, still “artifacts” such as unsuppressed, dominant carrier or unstable gain remain there for some hundreds of millisecs. I saw that the wiki states “perhaps a second” as the LO settling time. But can anybody confirm the above behaviour analysis ? best regards vince ---
**Author:** ![Vincenzo\_P](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/e274bd/32.png) [@Vincenzo\_P](https://www.ruby-forum.com/u/Vincenzo_P)\ **Post date:** [September 26, 2012, 9:07pm UTC](https://www.ruby-forum.com/t/usrp-lo-relocation-latency/223245/2 "2012-09-26T21:07:48Z")
On 09/26/2012 01:00 PM, Vincenzo P. wrote: > It looks like the LO responds to the steering command in some milliseconds > to about two tens of millisecs, > still “artifacts” such as unsuppressed, dominant carrier or unstable gain > remain there for some hundreds of millisecs. > > I saw that the wiki states “perhaps a second” as the LO settling time. > But can anybody confirm the above behaviour analysis ? It depends on the daughterboard. SBX and WBX have a worst case settling time of about 300us according to the ADI docs. You should also be able to schedule tuning through time commands so that the window of “interruption” is explicitly between time X and X + 300us. Here is some psudo code involving using timed commands to tune: [http://files.ettus.com/uhd\_docs/manual/html/sync.html#align-los-in-the-front-end-sbx-wbx-n-series](http://files.ettus.com/uhd_docs/manual/html/sync.html#align-los-in-the-front-end-sbx-wbx-n-series) -josh ---
**Author:** ![Vincenzo\_P](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/e274bd/32.png) [@Vincenzo\_P](https://www.ruby-forum.com/u/Vincenzo_P)\ **Post date:** [September 27, 2012, 11:09am UTC](https://www.ruby-forum.com/t/usrp-lo-relocation-latency/223245/3 "2012-09-27T11:09:48Z")
Hi Josh, thanks for the answer, so you confirm times in the range of the hundreds of micro secs? are WBX and SBX the best performing daughterboards in this repsect? where can I find the ADI docs you quote in your email? thank you and best regards. vince 2012/9/26 Josh B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![Vincenzo\_P](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/e274bd/32.png) [@Vincenzo\_P](https://www.ruby-forum.com/u/Vincenzo_P)\ **Post date:** [September 27, 2012, 2:05pm UTC](https://www.ruby-forum.com/t/usrp-lo-relocation-latency/223245/4 "2012-09-27T14:05:05Z")
> Hi Josh, thanks for the answer, > > so you confirm times in the range of the hundreds of micro secs? > are WBX and SBX the best performing daughterboards in this repsect? > > where can I find the ADI docs you quote in your email? > Both boards use the ADF4350 synthesizer. Analog devices has datasheets > available on their website.