When I transmit a signal at a certain frequency there is a large spike at what I have set the center frequency of the USRP. My signal does not have this large spike, because it is the LO of the USRP. We take care of this in things we write ourselves, but I can't find the documentation to do it for the GRC block. Here is the code I would normally use to tune the LO to something else, but still have my signal appear at the center frequency I would like
usrp::multi_usrp::sptr u2;
u2 = usrp::multi_usrp::make(dev_addr_vec[usrpId]);
...
uhd::tune_result_t tune_res;
// tune with lo offset
offset_freq_Hz = usrpConfig->rx_lo_offset_MHz * 1e6;
uhd::tune_request_t tune_req(usrpConfig->rx_freq_Hz, offset_freq_Hz);
tune_res = u2->set_rx_freq(tune_req);