Hi All, I have a project to monitoring ( air sniffer ) the data between GSM BTS and MS using UmTRX. Uplink Transmission is delayed 3 slots than downlink from specification. So when I sync. with BTS and get the downlink slot data, I must switch the freqs of receiver from downlink to uplink in less than 2 slots. When the program call 'usrp_dev->set_rx_freq(wFreq)', How much time does the UmTRX switch to the 'wFreq' ? Thanks in advance. ________________________________ Jiang WenYi

Hi Jiang. Please remember that Rx and Tx of LMS can't work well at the same frequency due to PLL's problems. Also, please do not forget about TxLO leakage which is quite significant. Best regards, Andrey Sviyazov. (Sent from my mobile client) 07.06.2013 14:36 пользователь "jiangwy" <wyjiang(a)ljshuoda.com> написал:

** Hi Andrey. I see. But what's the TxLO leakage? ------------------------------ jiangwy *From:* Andrey Sviyazov <andreysviyaz(a)gmail.com> *Date:* 2013-06-07 19:14 *To:* wyjiang <wyjiang(a)ljshuoda.com> *CC:* umtrx <umtrx(a)lists.osmocom.org>rg>; Chemeris Alexander<alexander.chemeris(a)gmail.com> *Subject:* Re: Re: Time to Switching Frequence Hi Jiang. Sorry, I missed that you'll use only receivers. So, no any problems in this case. Best regards, Andrey Sviyazov. (Sent from my mobile client) 07.06.2013 14:54 пользователь "Andrey Sviyazov" <andreysviyaz(a)gmail.com> написал: > Hi Jiang. > > Please remember that Rx and Tx of LMS can't work well at the same > frequency due to PLL's problems. > Also, please do not forget about TxLO leakage which is quite significant. > > Best regards, > Andrey Sviyazov. > (Sent from my mobile client) > 07.06.2013 14:36 пользователь "jiangwy" <wyjiang(a)ljshuoda.com> написал: > >> ** >> OK. >> Thank you and Sylvain very much! >> >> ------------------------------ >> jiangwy >> >> *From:* Alexander Chemeris <alexander.chemeris(a)gmail.com> >> *Date:* 2013-06-07 18:12 >> *To:* wyjiang <wyjiang(a)ljshuoda.com> >> *CC:* UmTRX <umtrx(a)lists.osmocom.org> >> *Subject:* Re: Time to Switching Frequence >> Jiang, >> >> It's not tested. LMS6002D chip by itself has quite short tuning time, >> but the current host and FPGA code introduce significant delay. I >> can't find exact numbers regarding LMS tuning time, but IIRC it was >> shorter than a GSM timeslot. >> >> So, as Sylvain said, given software limitations it's easier to use two >> channels of UmTRX to receive on two frequencies. >> >> On Fri, Jun 7, 2013 at 11:21 AM, jiangwy <wyjiang(a)ljshuoda.com> wrote: >> > Hi All, >> > >> >> > I have a project to monitoring ( air sniffer ) the data between GSM BTS and >> > MS using UmTRX. >> >> > Uplink Transmission is delayed 3 slots than downlink from specification. >> >> > So when I sync. with BTS and get the downlink slot data, I must switch the >> > freqs of receiver from downlink to uplink in less than 2 slots. >> >> > When the program call 'usrp_dev->set_rx_freq(wFreq)', How much time does the >> > UmTRX switch to the 'wFreq' ? >> > >> > Thanks in advance. >> > >> > ________________________________ >> > Jiang WenYi >> >> >> >> -- >> Regards, >> Alexander Chemeris. >> CEO, Fairwaves LLC / ООО УмРадио >> http://fairwaves.ru >> >