1 Which LNB too choose..
basically there exists two types of LNB:
- DRO don't use.. too unstable!!
- PLL good, see below...
1.1 Do I need to modify the PLL-LNB
- ext. Reference clock (GPSDO)
1.1.1 SDR Console
If you intend to use a complete software solution like SDR-console for receive, than just a PLL-LNB without any modification is enough!
SDR Console is able to use PSK middle beacon on the narrow band transponder to compensate the LNB automatically..
1.1.2 Down Converter
If you plan to use a down converter for receive, the best method is an ultra stable external reference clock based on GPS (GPSDO).
The AMSAT-DL Downconverter can supply the LNB and it's internal mixers based on such a reference from GPSDO. The same reference is also used for the Up converter..