Just an update. I'm QRV, DD0KP borrowed me a transverter while I'm waiting for my own one. Made one QSO with 100mW in SSB, my signal was 14dB S/N peak. With the 2 W amp I'm reaching beacon level. Transmitting works now after correcting a mistake I made with the patch .
The other optimisation was moving the radom closer to the lens. See picture. Now it must be very close to the optimum feed point. The distance from the lens is only a few mm to the cap,
The Venton LNB has an excellent dieletric lens but is too far away form the best feed point. See results below.
Here the patch now correct and closer to the cap (removed for the photo):
Some results with the A71A DATV beacon (HD-BP2 LNB still unmodified):
Venton Rocket Lens LNB seen as in picture: MER 5.2dB D2
POTY with POTY lens but without radom: MER 6.9dB D4
POTY with Venton Rocket Lens, but without radom: MER 8.8-9.0dB D6
POTY with Venton Rocket Lens, radom old position: MER 7.7dB D5
POTY with Venton Rocket Lens, radom new position: MER 8.7-8.9 dB D5/6
I think that's OK. My old Hirschmann dish got back into life (it was installed there more than 25 years ago).
73 Mike