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Thread: RHCP combined with LHCP: Why does this work?

  1. #1
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    RHCP combined with LHCP: Why does this work?

    Hi all,

    I just realized that I have a LHCP antenna (http://www.hobbyking.com/hobbyking/s...51623&aff=1514) on the VTX (http://www.hobbyking.com/hobbyking/s...63114&aff=1514) of my mini quad and a RHCP antenna (http://www.hobbyking.com/hobbyking/s...49827&aff=1514) on my receiver (http://www.hobbyking.com/hobbyking/s...18649&aff=1514).

    I can fly away several hundred meters with my mini quad and I still have a good picture.

    Why does this work? Shouldn't mixing LHCP with RHCP result in a very very very low (if at all) range?

    I'm very confused right now ... can anyone please elaborate why this works?

    Many thanks and all the best,
    Michael

  2. #2
    Just think how much better it will work when you get a matched set.

    Just because you pinched a hose, it does not mean NO water will get through.
    Flying through the cash.

  3. #3
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    Many thanks for the reply.

    I was always under the assumption that I would get no signal at all when mixing RHCP and LHCP. I did not expect that I would get a range of 200-300 meters (I did not fly farther) with a 200 mW sender even with those mismatched antennas.

    Now I can't wait to get the fitting antennas (ordered some mor of those IRC spironet v2) in order to enjoy the hopefully much better performance.

    All the best,
    Michael

  4. #4
    Instructor Pilot Channel 1's Avatar
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    Quote Originally Posted by daneel View Post
    I was always under the assumption that I would get no signal at all when mixing RHCP and LHCP. All the best,
    Michael



    With perfect polarization that might be so, but there really is no such thing in the real world and even less in the hobby world.


    The ratio of copolarization to crosspolarization which correlates with the antennas axial ratio determine the antennas ability to radiate a perfect CP signal and it's ability to reject the opposite polarization, in the commercial world such as satcomms and FM broadcast antenna designs can produce an almost a zero axial ratio and in the hobby world some name brand antennas (not cheap Chinese knockoff's) come close, but neither are perfect which is why channel separation is also required.


    Make sense?


    Wayne
    Everybody loves a bunny.

  5. #5
    Engineer for Jesus Christ IBCrazy's Avatar
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    What Wayne is saying is that the axial ratio of your antennas is very low so eventhough the rotation is reversed, it still works, just poorly.

    Basically you are running on 25% of your signal, that's all.

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

    videoaerialsystems.com - Performance video piloting

  6. #6
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    As others have said... the fact that it works so well is testimony to the fact that the antennas are actually pretty crappy. If they were good antennas (with a good axial ratio), then you'd get much worse results with mismatched polarization like this.

    Remember that if your antennas are this bad, they're not going to be doing a very good job of rejecting reflections either so you're losing one of the key advantages of using a CP antenna in the first place.

  7. #7
    Grasshopper Reliku's Avatar
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    The three major experts on the subject of this forum are all in agreement, so it must be true
    Cheers,
    Sven
    Quote Originally Posted by c5galaxy engineer View Post
    Zee is wrong, Grasshopper is ALWAYS right!

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    Indeed, I feel kinda honored just by the fact of _who_ actually replied to my question. Have been following you lightly a while IBCracy (and your self-built antennas) and I love your YouTube channel Bruce.

    I've now ordered some more of the RHCP IRC Spironet antennas and can't wait to replace those cheap LHCP ones.

    Many thanks for your replies.

    All the best,
    Michael

  9. #9
    I will just dig this thread out - sorry for that. I recently started to fly minuquad with my friend. When one flies freestyle up to 500m away the other one watches his flight through his fpv goggles with his rx. Now I realized that he uses RHCP while I use LHCP. But we can see really no difference (well, if I have really bad signal behind trees he has dropouts). Strange... I really thought that the difference will be more noticeable.

  10. #10
    Instructor Pilot Channel 1's Avatar
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    Quote Originally Posted by Stuclik View Post
    I will just dig this thread out - sorry for that. I recently started to fly minuquad with my friend. When one flies freestyle up to 500m away the other one watches his flight through his fpv goggles with his rx. Now I realized that he uses RHCP while I use LHCP. But we can see really no difference (well, if I have really bad signal behind trees he has dropouts). Strange... I really thought that the difference will be more noticeable.
    What kind of antennas are you two using?

    Wayne
    Everybody loves a bunny.

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