Unable to get twin LNB setup to work for Astra 1 and 2

#1
In order to receive Astra 1 and Astra 2 signals, I have 2 quad LNBs on one dish, fed to 4 different rooms via a switch (type unknown – hidden in the roof)
With my Medion set top box, I receive all FTA English and German channels without any problem.
Using ProgDVB (currently 6.48.01) with either of my two Pinnacle PCTV boxes (a 400e and a 450e), when I do a channel search, I can only find Astra 2 channels, irrespective of the settings I use, even if I set it to search Astra 1 only.
Somehow I suspect the answer lies in the Diseq settings, and have tried many different settings to no avail.
Can anyone help please?