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Amplifier entirely kills reception

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  • Amplifier entirely kills reception

    Hey all! I built myself a coaxial collinear antenna (to the instructions from balarad.net), with a quarter lambda stub as a filter. It has been working perfectly for a few days now.

    I wanted to try and boost my signal a bit more by adding an amp (the one on the picture) that I connect to the T adapter between the antenna and the quarter lambda stub using a F-F male bridge that has the same impedance like the coax I used for all the lines. You can see the bridge on the picture too. Now, as soon as I put the amp in the line, I completely lose all reception whatsoever. Reconnecting the system to exclude the amp brings things back to normal. I put the amp so that 'in' is coming from the antenna and 'out' is going into the T adapter. The photo may depict a different configuration, so just to make that clear :-)

    Any idea why this might be occuring and how to solve it? I read around that having an amp might be overloading the dongle, but I thought the quarter lambda stub should take care of most of the large RFI like the GSM bands?

    Thanks a lot! Cheers!

  • #2
    How did you power the amplifier?
    Satellite amplifiers generally require 14 ~ 18 V dc
    Without power, they will attenuate the signal severely instead of amplifying it.
    Last edited by abcd567; 2020-02-26, 02:33.

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    • #3
      Ah so! There's a noob mistake. Thanks for pointing that out. Do you have a smart way of powering it?

      Thanks a lot!

      Cheers!

      EDIT: I read around a bit and ordered myself an 18V power supply with F-plug. Is it enough if I just plug it into a T-adapter? Although I assume the placement in the circuit doesn't really matter, I'd like to place it between the filter and the antenna, where the amplifier also lives. Is there something wrong with this approach? Thanks a lot for your help!
      Last edited by markomne; 2020-02-26, 09:23.

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      • #4
        The DC Power inserter for Satellite in-line amplifier should be connected between DVB-T and Satellite Amplifier. You will also need an AC to DC adapter (AC to DC 12V ~ 18V) to feed DC to the amplifier through power inserter.

        Search ebay & amazon to find a suitably priced power inserter. Below are few examples.

        https://www.ebay.com/itm/221457117112

        https://www.ebay.com/itm/371642600548

        https://www.ebay.com/itm/193252704809


        SETUP
        Two power inserters are used,
        - one for inserting DC on coax so that it reaches the amplifier

        - other as dc blocker to prevent dc to reach antenna in which core & shield are shorted at some point
        Satellite Amplifier Setup.jpg
        Last edited by abcd567; 2020-02-26, 10:57.

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