Sorry Remco, I cound not resist this wordgame in the subject
So Folks, here's a new (?) idea for injecting an external TCXO, which I successfully tested.
Just leave the x-tal where it ist, disconnect the LO out pin of the PLL-Chip, and inject the external LO at the x-tal.
I tested succsessfully this method with 2 Diavolo Twin V2 and one Diavolo Quad V2.
This method has some advantages :
you don't have to remove the x-tal
you can easily go back to internal LO (original)
the external LO signal will be filtered by the x-tal
easy to implement
so many advantages
The value of R1 in my shematic determins the sensivity and optimal level of the external LO.
With 820 Ohm at a RT320M chip it is optimized for 1Vss LO input.
For other levels you should make your own experiments.
The value of R2 in my shematic depends on which impedance and coax cable you use.
68 - 82 Ohm is fine for 75 Ohm systems.
47 to 56 Ohm is fine for 50 Ohm systems.
But this value is actually less important.
This method is not useful for (older) NXP chipsets.
Therefor you better take a look at Remco's Subject : other-method-to-inject-external-ref-into-lnb