I do see in the documentation that the tune result "target_rf_freq" will match the tune request "rf_freq", which it does in my example below. So, I suppose the output shown is as expected for my request. Unfortunately, this doesn't solve my problem of the actual spectrum being wrong. I may have to construct a test case to show that the problem is in UHD....
On Thu, Apr 18, 2019 at 1:50 PM Marcus D. Leech via USRP-users <usrp-users@lists.ettus.com> wrote: > > On 04/18/2019 01:44 PM, Rob Kossler via USRP-users wrote: > > Hi, > I am seeing some strange (and unrepeatable) behavior with an X310/UBX-160 and > the multi_usrp->set_rx_freq() function. I call this function with a > tune_request that I create with a desired target frequency & lo_offset. The > output below shows a "pp_string" of the request and the result (for the > request, I had to create my own "pp_string" function but for the result, I > used the existing Ettus function). > > I can tell from the resulting spectrum (not provided) that the frequencies / > offsets are often not getting set correctly because I have a CW tone at a > known frequency coming in. But, what I am presently interested in is the > output shown below. In this example, I requested a target frequency of 2450 > MHz with a 5 MHz LO offset. The tune request looks like I would expect. > However, for the tune result, shouldn't the "Target RF freq" match the > "Target freq" from the request (i.e., 2450 MHz rather than 2455 MHz)? > Rob > > // This is essentially the code executed > tune_request_t tune_req(2450e6,5e6); > tune_result_t tune_res = usrp->set_rx_freq(tune_req,0); > > // here is the output showing to_pp_string() > Tune request > RF Policy: M > Target freq: 2450.000000 (MHz) > RF freq: 2455.000000 (MHz) > DSP Policy: A > DSP freq: 0.000000 (MHz) > args: > > Tune Result: > Target RF Freq: 2455.000000 (MHz) > Actual RF Freq: 2455.006105 (MHz) > Target DSP Freq: 5.006105 (MHz) > Actual DSP Freq: 5.006105 (MHz) > > The "Target RF Frequency" is the frequency setting of the LO, which if you > are requesting a 5MHz LO offset, will be somewhere around 5MHz away from > your target "sky" frequency. The DSP arranges to "mop up" the difference. > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
