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<blockquote data-quote="deeptho" data-source="post: 1143390" data-attributes="member: 215446">Apparantly the spectrum problem is more complicated than I expected. Below are four spectra captured within a few minutes of 42.0E. The blue line at 18700 is the currently selected mux and can be ignored.The horizontal lines abox muxes can be ignored as well. What is striking is that the peaks vary a little in frequency. I did not nituce that before.Also the baseline seems to shift. The bottom spectrum is for 19.2E and shows similar but not equal effects.What is also really strange is the perfectly flat part of the specctrum near 18.85Ghz. Perhaps that is related to the polarising plate.I wonder if there might be some relation with automatic gain control or to the LNB heating up. It is difficult to explain the variationsin the baseline, but it could of course also be something in the tbs6909x card or the way it reacts to this lnb signal. I do have an USRPhere, so I will test later some time with that.The spectrum acquisition takes about 20 seconds and is captured about 50 or 60 Mhz at a time (don't remember exactly), but the code attempts to make&nbsp; neighboring parts of the signal &quot;continuous&quot;, which can explain why the orange line suddenly jumps up between 18.6 asnd 18.7 GHz:the spectrum parts are captured at slightly different times.[ATTACH=full]147850[/ATTACH][ATTACH=full]147851[/ATTACH]</blockquote>

[QUOTE="deeptho, post: 1143390, member: 215446"] Apparantly the spectrum problem is more complicated than I expected. Below are four spectra captured within a few minutes of 42.0E. The blue line at 18700 is the currently selected mux and can be ignored. The horizontal lines abox muxes can be ignored as well. What is striking is that the peaks vary a little in frequency. I did not nituce that before. Also the baseline seems to shift. The bottom spectrum is for 19.2E and shows similar but not equal effects. What is also really strange is the perfectly flat part of the specctrum near 18.85Ghz. Perhaps that is related to the polarising plate. I wonder if there might be some relation with automatic gain control or to the LNB heating up. It is difficult to explain the variations in the baseline, but it could of course also be something in the tbs6909x card or the way it reacts to this lnb signal. I do have an USRP here, so I will test later some time with that. The spectrum acquisition takes about 20 seconds and is captured about 50 or 60 Mhz at a time (don't remember exactly), but the code attempts to make neighboring parts of the signal "continuous", which can explain why the orange line suddenly jumps up between 18.6 asnd 18.7 GHz: the spectrum parts are captured at slightly different times. [ATTACH type="full"]147850[/ATTACH][ATTACH type="full"]147851[/ATTACH] [/QUOTE]

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