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Thread: Truncated cone reflector for Helical antennas.

  1. #21
    Banana Drone Flying Monkey's Avatar
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    Quote Originally Posted by Wearyman View Post
    What if you fly behind yourself? Or out of the beam? Its not like you can see the plane at that range.
    If you're going more than ten miles out... You're gonna fly in a particular direction with some idea of a flight plan and where your plane is in relation to you... Fly out, turn around and come back. I wouldn't think you'd have enough battery to fly out ten miles, then circle around yourself. But if you have your controller's tx directional antenna on a tripod you'd aim it the same direction as your directional vRx antenna as well. If you have to re-aim your vrx antenna then re-aim your Tx at the same time.
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  2. #22
    Navigator Kondor-FPV's Avatar
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    Quote Originally Posted by Wearyman View Post
    What if you fly behind yourself? Or out of the beam? Its not like you can see the plane at that range.
    It's quite simple, I have a tracker on the ground that receives gps coordinates from the plane in flight, (it knows its position before flight), and tracks the plane, all I have to do is aim in the same direction as the video antenna tracker, but there is a simple way to do that, I fly in front of me, and go out a few km, I have the rssi % at the top left corner of the screen, If I see the rssi getting lower, I turn the antenna until I see the rssi go up again, I move left than right, up and down a bit, until I find the best rssi displayed through the osd....
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  3. #23
    FPV addict ke123's Avatar
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    Other than it being large, why not use this for 1.3ghz too? Roberto Montiel could go 200km!

  4. #24
    ^(_MăĻēŜĐ_)^ ЯuĽe U MoRaLeSD's Avatar
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    I am about to built a Bixler for FPV and I think to use 1.3 or 5.8 frequency. I already have 2x 1.3 RXs but shall I use 5.8 instead?
    I have antenna tracker and 2nd antenna in Eagle Tree Diversity(I know it's excessive). So is it worth it to run it in 5.8?

  5. #25
    Navigator Kondor-FPV's Avatar
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    Quote Originally Posted by MoRaLeSD View Post
    I am about to built a Bixler for FPV and I think to use 1.3 or 5.8 frequency. I already have 2x 1.3 RXs but shall I use 5.8 instead?
    I have antenna tracker and 2nd antenna in Eagle Tree Diversity(I know it's excessive). So is it worth it to run it in 5.8?

    5.8 has a size advantage, I would use it for close in flying, as it can give you consistent 6-7 km range with a good helical on the ground, and more if the weather conditions are very good, but it's harder to tune the antennas, and the antennas are easily detuned by mist, clouds, humidity, heat, and anything else.

    1.2-1.3 are huge but have a HUGE range advantage, you can do 12km with 2 omnis... no trackers, no directionals needed...

    I find that amazing.
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  6. #26
    Navigator Kondor-FPV's Avatar
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    Quote Originally Posted by ke123 View Post
    Other than it being large, why not use this for 1.3ghz too? Roberto Montiel could go 200km!
    hehe, that's if he can stay awake thermaling for 10 hours )
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  7. #27
    ^(_MăĻēŜĐ_)^ ЯuĽe U MoRaLeSD's Avatar
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    Quote Originally Posted by Kondor-FPV View Post
    5.8 has a size advantage, I would use it for close in flying, as it can give you consistent 6-7 km range with a good helical on the ground, and more if the weather conditions are very good, but it's harder to tune the antennas, and the antennas are easily detuned by mist, clouds, humidity, heat, and anything else.

    1.2-1.3 are huge but have a HUGE range advantage, you can do 12km with 2 omnis... no trackers, no directionals needed...

    I find that amazing.
    So it's better to use the 1.3. I already have a SPW and a 10Bic Crosshair in the ground with a CL on the Platform, so I don't need more hehe

  8. #28
    Navigator Kondor-FPV's Avatar
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    Quote Originally Posted by MoRaLeSD View Post
    So it's better to use the 1.3. I already have a SPW and a 10Bic Crosshair in the ground with a CL on the Platform, so I don't need more hehe

    Yes, if you are happy with 20-30km than you don't need "more". If you want to break records, you need "more"
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  9. #29
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    Kondor can you offer a bit more info on how to build the trunctuated reflector?

  10. #30
    [QUOTE=
    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

    [/QUOTE]
    I am particularly interested in the reflector. Is this your design? How well did it work? Reflector design seems to have a large influence on the overall performance and I was getting ready to do some simulations to work on the grid which is much more practical that a solid cone. That looks like a lot of work that I would like to avoid. Here is some info I found in the literature (ON THE OPTIMAL DIMENSIONS OF HELICAL ANTENNA WITH TRUNCATED-CONE REFLECTOR andOptimization of Helical Antennas) using a solid rather than mesh reflector up to 4.5 dB improvement over infinite ground with 5λ diameter 2 λ high reflector. Pitch and impedance depends on wire radius. I noticed that one boom with optimal reflector is same as 2 with aperture covering reflectors. I tried to post a short table but the formatting seems to have used 40KB so I had to delete it.
    Last edited by robeyw; 24th January 2015 at 06:02 AM. Reason: typographical error

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