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Leif Asbrink leif at sm5bsz.comHello Steve, > > We still have to add functions to set the IF-gain from external > > applications, this is something on the todo-list. > OK. Do you have an idea about the time scale? It would be > a good thing from my perspective if this would be implemented > before I release the next Linrad version. Since there was no response on this I have released a new version of Linrad with new versions of rtlsdr.c and tuner_e4k.c to go with it. Performance is now quite good. The noise figure is 7 dB with a dynamic range of about 74 dB (saturation vd MDS in 500 Hz.) When gain is reduced for a noise figure of 10 dB the dynamic range is 80 dB, 6 dB below the theoretical limit. http://www.sm5bsz.com/linuxdsp/hware/rtlsdr/rtlsdr.htm The gain setting is clumsy, I just added some things that seem similar to the existing routines. It seems to me that a new approach would be desireable. If one wants to set the gain of the E4000 chip by use of a single parameter one has to use some of theIF gain controls as well as the mixer gain and the lna gain. I have not been able to see any effect of the enhanced gain. I tried various bits blindly and found a setting that eliminates the AGC in the RTL2832 chip. That is a significant part of the performance improvement. Today the rtlsdr with Linrad under Linux is not a toy. It is a surprisingly good SDR receiver (in relation to cost.) Performance is about 20 dB below what we find in standard transceivers like IC706MKIIG and others. I do not know how to proceed. I see two options: 1) librtlsdr is rewritten with a gain setting routine that operates on lna, IF and mixer gains in a way that optimizes performance. 2) I will provide a Linrad specific library that supports only the RTL2832/E4000 combination. I expect the simple change required to disable AGC in RTL2832 to be implemented pretty soon. Hopefully ExtIO_RTLSDR.dll and SDRSharp will soon be updated to remove the AGC. A gain setting function would surely make these softwares far more useful. I think the best way of setting the e4k gain would be to place a matrix in tuner_e4k.c with as many rows as the number of stages that we want to use for gain setting and as many columns at the number of different nominal gains ẅe want to supply. That would be a lot of code to remove and not much to add - but I do not wish to take desicions for osmocom. Linrad-04.40 still uses its own callback and I may have to supply source code for todays version of tlsdr to go with it. In case the standard library from osmocom implements AGC off and a sensible routine for manual gain control I will adapt Linrad to the standard library. Regards Leif / SM5BSZ