External 25Mhz reference vs. signal strength?

  • It doesn't, if you do it right, that is, the circuit you're using to filter out the 25 MHz reference doesn't put a load on the 739 Mhz signal. Keep in mind that the coupling happens using a series resonant circuit that gives a high impendance except at the resonance frequency 25 MHz.


    But, even a little attenuation does not hurt. Keep in mind that the input of the LNB defines the noise figure (and you're not touching that) and these things have a lot of gain (30-50 dB I read somewhere, not sure if this is right).


    In any case, even if you'd load the 739 MHz a bit, there is plenty of signal and you probably won't notice.


    At the same time, the original reference crystal oscillator smears signals a bit, but using the reference signals are sharp. Expect clarity of the signals to go up, depending on the stability of the xtal oscillator this can be quite a bit.