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Thread: Truncated cone reflector for Helical antennas.

  1. #1
    Navigator Kondor-FPV's Avatar
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    Truncated cone reflector for Helical antennas.

    Hello guys,
    this is the solution to add a couple of db to the gain of our Helicals.

    The antenna in the picture is a 5705 Mhz 16 turrn helical with 19dbi gain...

    The truncated reflector adds another 2dbi as opposed to a flat plate reflector.

    To build the reflector, the bottom side of the truncated cone has to have a diameter of 0.75 λ , and the top side of the cone has a diameter of 2.5 λ -- depth is 1/2 λ

    It can be useful for 5.8 and 2.4 antennas for VERY long range, with trackers.

    This antenna in the picture is a record contender...as we know 19.6km has been done with a 12turn helix and flat plate reflector on 5.8ghz.

    Will report back as soon as I am ready to fly it.
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    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  2. #2
    Crashing Vitamin J's Avatar
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    Whoa :drool:

  3. #3
    Navigator Kondor-FPV's Avatar
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    I take that as a compliment... a few pictures of the build process.

    calculations, cad design, cnc milling of the copper backplate including the arms that will be bent up and have the solder point to build the grid.

    That's a lot of soldering and shaping. Than of course there is cnc milling of the g-10 for 16 turn helical, and the winding of it which is not so easy either.
    Finally there is the tuning with a wave trap matching section. Tuned on 2 different transmitters on channel 1 5705 swr 1.15:1 as is usual for my helicals.
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    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  4. #4
    Banana Drone Flying Monkey's Avatar
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    Wow! ET could use that to phone home!

    Great work!
    "You can't take the sky from me"

  5. #5
    Engineer for Jesus Christ IBCrazy's Avatar
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    !!! Nice work! Very nice work. I never considered using something like that. Where is the focal point?

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    videoaerialsystems.com - Performance video piloting

  6. #6
    Navigator Kondor-FPV's Avatar
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    Hello Alex, it's not a parabolic reflector, in that case I would have used a backfire helical with 3-4 turns. It's just a cone shape, so it doesn't have only one focal point. From the tech paper I studied it seems like the measures I gave are optimized for helicals from 10-16 turns.
    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  7. #7
    Engineer for Jesus Christ IBCrazy's Avatar
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    Then I guess it's time for a backfire unit isn't it? You might consider a CP patch, though for this. I have a good article on how to do this and I designed the TBS CP Patch. If you revese the polarity and feed it into a dish, you should get 19dbic.

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    videoaerialsystems.com - Performance video piloting

  8. #8
    Navigator Kondor-FPV's Avatar
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    Yes, it would be interesting to try a backfire with few turns for better efficiency.

    As far as cp patches, that is also very interesting. The backfire helix as a feed tough is much cooler though!

    Now I will concentrate and see how far I can go with this baby, than the improvements will come.
    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  9. #9
    Navigator Kondor-FPV's Avatar
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    This is what the 16 turn can do with a dummy load on the tx, that's right! No antenna on the TX...

    All I have to do now is mount a Pinwheel and work up my courage to go 20+ km with my plane.

    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  10. #10
    ^(_MăĻēŜĐ_)^ ЯuĽe U MoRaLeSD's Avatar
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    With a 600mW ImmersionRC VTX and a combination of these antennas 5.8 GHZ tx Pinwheel for the VTX and 12 turn 5.8 helical long range antenna for the RX what would be the average Distance? Is there any way to know this?

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