Boost the LNB-Ref a little?

  • That's why I added a second buffer to the reference board. A simple common emitter transistor amplifier should be sufficient. It's only 25 MHz so no need for GHz capable RF devices. Just build it dead bug style.

  • But keep in mind to add a lo-pass filter after the last Amplifier to keep the signal sine form and not to "send out" harmonics.

    25 MHz x 3 = 75 MHz (security Band) and 25 MHz x 4 = 100 MHz (Public radio Band).

    Also you may disturb yourself in the SAT IF.


    Armin DF1QE

  • If you use a MMIC it does not need a low pass filter as far as it is below 1 dB compression point and the 25 MHz is clean.

  • Hello George !

    and the 25 MHz is clean

    Yes I agree .... IF it's clean and not any kind of digital signal ....

    But why always work with minimum components ?

    Are we chinese ?

    Shouldn't we as technicians not better try to optimize components ?

    1 or 2 chokes and 2 or 3 capacitors should not burst our ham budged.

    If I would build such an amplifier for myself it would have a high level MMIC, a regulated power supply with EMV components, a double Pi low pass filter at the output, and may be a damping regulator at the in- and/or output, and sure a tight metal case with good sockets.

    Is that to much for ham radio ?


    Armin DF1QE

  • IMHO there is a great learning experience in building things as cheap they can be given they do the job properly. And to know that you also need to be able to measure your work before putting it on the air, which is yet another learning experience.