I wonder if someone can help me? I have been trying to understand 'tuning' and I note that UHD has a couple of options for setting the centre frequency. The two methods: tune_request_t( target_freq ) method1
and tune_request_t( target freq, lo_off) when I try the former in GNURadio Companion for a source of UHD things work as I expect but when I decide to put in a lo_off I get strange results. uhd.tune_request_t(804.75*e6, 40*e6) and I have enabled the dbsrx2_debug flag to true to see how things are being driven and can see the following when I execute the GRC, it says: Target 844.75 and actual 844.75 which seems correct (i.e. what I think I asked for) but then I get: setting of regs x00 through x07 and then Warning: The hardware does not support the requested RX frequency Target 804.75 Actual: 868.75 but it receives the 804.75 signal (or thereabouts - tv audio so wideish bandwidth)! The s/w is calculating the correct integer and fractional values in N (ext_div of 4 (HMC426), scaler 4 (since freq < 1125Mhz ) etc. Some questions: 1) why is 844.75 not valid ? From the MAX2112 spec there are VASA/VASE signals which allow the chip to search/select VCOs but cannot see where these are set and assume that is the reason that 2) why is the utility talking about 868.75? 3) why, when it says actual is 868.75, is the system receiving signals on 804.75? 4) if you can direct the tuner to a specific frequency with method1 , why would you consider having the option to specify an lo_offset? would it allow an IF to be generated (e.g. 10.7 MHz)? Kind Regards, John _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio