Thank you for the instructions.
I just tried to use the simplest possible set up for the Down Converter. Unmod. LNB -> Down Converter (no GPS, but either external clock reference of 10MHz from the osci or nothing at all) -> Pluto. I set the Jumper to 14V supply for the NB and 25 MHz, removed the connection between WB out and NB in and connected the LNB to the NB in as you suggested. I also configured the I/O device in Gqrx to 2 MHz bw.
Then I swept through the spectrum in 100 KHz steps from 140 MHz to 150 MHz. But I coudn't see any of the beacons. somewhere around 146 MHz there was a very high peak. But It appeared out of the blue. It was suddelnly in the middle of the screen instead of shifting in with 100 KHz steps as i was sweeping. Do you ave any idea what might cause this or if its related to the problems I have?
Alright, it seems you are not a ham-radio operator, otherwise you'd knew what a handheld or walkie talkie is.
Yes, I am not ... yet.
Ok, 40ish MHz an 25ish MHz is good! Means the TCXO in V3D is working and you have output, just not disciplined by GPS.
Now, who modified the LNB? Was it someone who can check it ?
Great that means there is hope.
I have the modified LNB from the Shop here (https://shop.amsat-dl.org/produkt/qo-100-modifizierter-lnb/). So guess I could sent it back to be checked but I would like to be sure that it is really not working before I do so. And as things are going i Suspect there is something wrong with the V3D rather than the LNB. (I connected the bias tee to the Pluto and unmod. LNB again just to be sure the antenna and LNB are still correctly aligned and I was able nicely see the beacons and transmissions around 740 MHz)
Do you have how i could further test whats wrong with the V3D?