LNB downstream and LO upstream over 1 coax

  • I saw at homebrew solution at ON4CJQ running both signals over 1 coax to the LNB.

    Has anyone done this also?

    I am working on my own implementation of this so that I can reduce the cabling to the LNB head.

    But before launching pcb production just want to check if it exists already.



  • Hi,

    Can you provide the link of the ON4CJQ solution? Also keep us informed about your progress. I use 25 MHz+740+bias and 430 for the other cable. I run about 60 meters. A Lab testing can be personal run from September. Also I use a second cable for H. Maybe a combiner can be used also to use a single cable for NB and WB signals. One question to the designers of QO100 is why NB and WB use different polarization?

  • Johan,

    many people are using the cable from the LNB to the receiver to send 3 "signals" over the single cable:

    - the receive IF signal e.g. 740 MHz

    - the supply voltage for the LNB including the information to switch between V and H polarization (14v / 18V)

    - the reference frequency signal for the LNB (typ. 24, 25 or 27 MHz)

    Sending the local oscillator signal for the LNB upstream will be very difficult as it is a rather high frequency
    and the attenuation of the cable will be very high.

    Triplexers for the above mentioned 3 signals are built into the AMSAT-DL downconverters and can be bought
    stand alone for instance in the BATC shop in UK (design by Mike Willis G0MJW). Here is a descrition of my built:


    Kind regards



  • Hi George,

    I am also not sure whether I understood what Johan wants to accomplish. So we need his response.

    In any case I think there are 2 "links" where multiple signals can be combined.

    1.) One is the receive path as I had described above,

    2.) The other is the path from the transverter to the transceiver where the RX-IF-signal, the TX-IF-signal and the reference signal can be combined. For the second topic I am using a triplexer from Diamond.

    You can find a description of ma portable setup (where both "links" are using multiplexing) here:


    Kind regards