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Steve Markgraf steve at steve-m.deHi, On 07.08.2013 11:49, Richard Ranson wrote: > Looking at the rtlsdr driver, I see that there seems to be some code to > correct the IQ balance, but I'm only going by the names of functions > like "_IQ_Tree" and "_Compare_Cor". The algorithm, if there is one, is > not at all clear nor of direct interest, the question is whether or not > there is some IQ balance built into the rtlsdr driver and does anyone > know how effective (e.g. in terms of image suppression) it is. What you're looking at is dead code in the r820t tuner driver (which presumably can correct the internal IQ-offset, as this is a low-IF tuner). But we're not using it right now, thus it is never called. For all the other tuners (which are zero-IF) we enable the internal IQ- compensation of the RTL2832, see [1]. However, it is not really documented and understood what that does, the observed effects are minimal. If you want to see for yourself you can disable the internal compensation, change that write to: rtlsdr_demod_write_reg(dev, 1, 0xb1, 0x03, 1); For software IQ-compensation we have the gr-iqbal GNU Radio block: http://cgit.osmocom.org/gr-iqbal/ Regards, Steve [1] http://cgit.osmocom.org/rtl-sdr/tree/src/librtlsdr.c#n562