Problem solved! Thank you very much for your suggestions.
A LTE/4G filter (which is nothing else but a ~790MHz low-pass filter) solved all my reception problems. Apparently, there was some unwanted hf from the surrounding cell sites affecting my QO-100 signal.
I noticed that some LNBs (including the one which had worked in my case) have an in-built LTE/4G filter. But some LNBs don't...
Thank you very much for sharing your ideas. So far, I have tried the Bullseye LNB which is supposed to work out of the box (I did not modify it by myself, it comes with a TCXO and is designed for QO-100). The two unmodified LNBs are a hb digital UHD 101S and a Skymaster. The UHD101S works (but it drifts of course).
dm4im: Actually, I feed 12V and not 14V. The Bullseye is supposed to work in vertical polarisation from 11.5V-14V. But maybe 12V are not enough. 14V are worth a try.
I have two unmodified LNBs and the Bullseye which comes with a TCXO. One of the unmodified LNBs works properly (with drift of course). The Bullseye (with TCXO) and one of the unmodied LNBs don't work as expected.
Dear all,
while trying to receive signals from QO-100, I observed a strange problem: the audio of the SSB signal is extremely scratchy, depending on the LNB.
Before identifiying the LNB as the culprit, I changed the SDR radio (Adalm Pluto vs. RTL Dongle), the software (SDR Console vs SDR Angel, including the latest updates), the DC source and I checked the Bias-T. I even changed the cables. Only after trying the third LNB, I had a clear audio signal.
What puzzles me is that two (Bullseye and a standard consumer LNB) out of three LNBs in my sample generate scratchy signals. Therefore, I assume that this might not be an uncommon problem.
Is there anybody who observed a similar signal and behaviour? Is there a way to solve this problem? Could it still be a software problem? Configuration? Help and ideas are highly appreciated. The reason why I'm asking is that I would like to work with the Bullseye. The one which works is not stabilised, yet.
73 de Timo
