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Illogical reception

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  • Illogical reception

    Hello all,

    I am a relative newbie, first started contributing on September 19.

    I have some experience with radio reception and well understand basic antenna design and construction. Since I started I have been trialling various homemade antennas and locations. In the early testing days i did not got one antenna to significantly outperform any others, so for simplicity sake I stuck with a simple dipole made from two 69mm lengths of coat hanger wire mounted vertically in a chocolate-block connector, connected to the DVB dongle by about 4m of RG 6 coax.

    With this very basic setup, I initially positioned the antenna outside an upstairs window, hanging beneath the glittering of the house by another piece of coat-hanger wire. Clearly not particularly high and only viewing 180 degs of sky. Nevertheless, reasonable success with a maximum range of 245 miles, though more regularly 190-ish. Happy with the idea that this antenna had proven the concept, I decided to commit to mounting it higher.

    CHANGING NOTHING OTHER THAN RAISING IT UP ON A PLASTIC POLE to almost above roof height, I was disappointed to see the results markedly deteriorate. Yes it could see more sky, but max range dropped to below 100 miles. Bringing it back down to guttering height increased the range once again. I then went back round the buouy of trying different antennas, positioned high and low, I even sucked in my pride and bought a commercial antenna, but each time the same result, better range when kept lower down.

    Can someone please explain this? Am I getting a positive reflection from the wall of the house?


  • #2
    Likely the gutter acting as a ground plane?

    Tends to focus the chunks of signal so you get the same portion of wave direct to the antenna rather than a top/bottom

    Chuck a tin can or pot lid of about 80mm diameter under it in the free space location and see
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers


    • #3
      I like your thought, but plastic glittering and the antenna is hanging 10 or so inches below glittering.



      • #4
        Don't you just love auto correct? Clearly glittering equals guttering!


        • #5
          You may have some powerfull interference nearby and you are shielding the antenna from it. At high frequencies attenuation is considerable. And your dipole has a quite wide band.
          Try a type of antenna with a narrow band like a coaxial collinear, should be as easy to do as a dipole. Try with just two segments, not much different than a dipole, or you may add more pairs.


          • #6
            Concuct scans of RF signals in your enviroment with:

            (1) Antenna below the gutter (where you get good reception)
            (2) Antenna high up (where you get poor reception).

            Use the method to scan given here:

            Do I need a Filter? - Find RF Signals In Area