how to get 3dB additional gain on wlan grid parabolic antenna

  • I hear some stations on Oscar 100 using comercial parabolic grid antenna for the uplink. It is linear polarized not circular.

    With 2 Watt you are good enough for qso´s but not so loud as the telemetrie beacon.

    I am also using this antenna. It has a low wind loading. But is the reflector a compromise or not? The distances of the grid is not very low. I tested with aluminium foil and had success. But to much wind load and solar reflection. I decided to try fly screen. It works as good as with the aluminium foil. I fullfil the surface of the backside of the antenna with this fly screen.

    3dB louder signal on the satellite. You can leave an amplifier. Try it, it works!


    73 de Frank, DL2GRF

  • Hi Frank, if you clad the reflector grid with fly screen you will certainly improve the reflective properties of the dish. However you will also increase the windload to the point, where a standard offset dish of same size will be on par at wind load and in terms of RF performance even better. And with a new feed (circular), you can improve by another +3dB .


    When it comes to wind, fly screen with its tiny mesh is unfortunately quite comparable to a solid sheet of metal. You can easily test this by hanging both on a 'Waescheleine' and have a look.

  • Hi Frank,

    did you use 'normal' fly screen for windows (non metal??) or a special one metal grid for basement shafts for the defense of mice?


    73 de Robert DL5GAC

    DL5GAC * Robert * Baienfurt-Köpfingen * JN47ut * DARC OV PØ9

  • Hello SAT-friends,


    a friend in my local club tried to string the parabolic grid antenna with "Windhager" aluminum screens.
    Result: No change in signal strength.
    Is there any further experience in this regard?


    73 de Robert - DL5GAC

    DL5GAC * Robert * Baienfurt-Köpfingen * JN47ut * DARC OV PØ9

  • Hello,

    are there any attempts which polarization with the grid antenna is the best for hail? Horizontal or vertical or both the same ?


    Does a fly screen bring more gain on the satellite?


    vy 73 Georg

  • are there any attempts which polarization with the grid antenna is the best for hail? Horizontal or vertical or both the same ?


    The QO-100 Uplink is RHCP circular polarization..

    So it does not really matter so much if you are horizontal or vertical polarized, but you will always loose half of your uplink power (-3dB) received by QO-100 because of using linear polarisation instead of circular polarisation...

    Peter Gülzow | DB2OS | AMSAT-DL member since 1983 | JO42VG

  • This is not quite true but in this case close enough. Firstly, none of your power will be lost but only half what could be received will be received. This means you are wasting power, as you are also be using a smaller dish and not focusing the power as tightly. If you had a pencil beam and could aim it well enough you would only need microwatts of RF power.


    The propagation loss for horizontal or vertical is not exactly the same all the time. The largest effect is due to the shape of raindrops. At 2.4 GHz this difference is almost negligible but not totally so. Vertical might have ever so slightly less loss, fractions of a dB in heavy rain. I could look up the ITU-R model but it's really not worth it. and would unhelpfully boost my technobore score. When we get to up linking at 10 GHz and 24 GHz this starts to matter.


    Mike