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Thread: New 1.2 GHz antenna , RCHP or LHCP 10.5dBi, super compact

  1. #11
    Navigator TurboCinqy's Avatar
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    No one? =(

  2. #12
    Engineer for Jesus Christ IBCrazy's Avatar
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    Quote Originally Posted by TurboCinqy View Post
    Hi,

    I'm trying to make some 1.3 halfspheres.
    Like you said a smaller reflector gives less gain.
    No or big center hole makes no difference.
    Only the outside of the reflector diameter.

    So now I also tried to add 3 lower turns (total of 8turns) beneath the halfsphere.
    Result is over 1dBm loss instead of more gain.
    Also the angle looks smaller.

    Vswr is fine so that isn't the problem.
    Everything else is the same.

    For the normal halfsphere I tried several types of wire but that doesn't have much influence on the output itself.
    How are you measuring gain? Wire thickness in a helical means very little. It typically just changes the bandwidth which is already extremely wide.

    The trick of this antenna comes down to matching it properly or you end up with some nasty sidelobes that kills your forward gain. Try adding or removing just 1/4 turn and you should see some changes. Remember that the helical begins to become a transmission line near the feedpoint and thus, the shorter this matching section is, the better results you will have.

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

    videoaerialsystems.com - Performance video piloting

  3. #13
    Navigator TurboCinqy's Avatar
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    I measure gain just for an indication.
    It's not reliable I think.

    I put a vtx with attenuator a few meters away from my desk and use the IRC power meter on dB settings to find the peak values.
    Works fine with directional antennas but not that good on omnidirectional. Get a lot of up and downs there.
    Don't have a clear 0 value as antenna so just comparing between identical or different antenna's.

    What do you mean by matching.
    Only vSWR or something else. Swr is most of the time only by tuning the feed point.

    Good to know it has to be a short as possible.
    In my case most of the time you should start as low as possible at feedpoint to get it almost right.

    Bandwidth you're right.
    That's why I use thin wire. It has a great bandwidth so with thin wire it gets a bit smaller. Still big enough for most Vtx channels.

  4. #14
    Engineer for Jesus Christ IBCrazy's Avatar
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    Quote Originally Posted by TurboCinqy View Post
    What do you mean by matching.
    Only vSWR or something else. Swr is most of the time only by tuning the feed point.
    When I am talking about matching a helical I am referring to the last turn of the helical being part of an impedance match for SWR. The mode of the helical changes from antenna to transmission line here and the longer this section is, the stranger the performance can be.

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

    videoaerialsystems.com - Performance video piloting

  5. #15

    New 1.2 GHz antenna , RCHP or LHCP 10.5dBi, super compact

    I love these still. My favorite antennas for 1.2ghz (1010-1.3). Compact enough that I run a pair in my backpack 60* offset in diversity with some LNA's and the coverage is just un-freakin believable.


    Sent from my iPhone using Tapatalk
    Last edited by Toysrme; 26th December 2016 at 03:23 PM.

  6. #16
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    Quote Originally Posted by Toysrme View Post
    I love these still. My favorite antennas for 1.2ghz (1010-1.3). Compact enough that I run a pair in my backpack 60* offset in diversity with some LNA's and the coverage is just un-freakin believable.


    Sent from my iPhone using Tapatalk
    Glad you like our antennas, they are still available at www.fpvlr.com
    converage on the half sphere 1.2GHz is preatty impressive!

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