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Thread: My first collinear antenna

  1. #171
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    Quote Originally Posted by FR24-BB8 View Post
    Hi guys.

    I'm new at this forum, and new to FR24 to. I've just set up my Raspberry 2 to feed FR24 with data, and with the stock antenna that came with my USB-dongle I get signals from approx. 20-50 nm. Tonight I built an collinear antenna with five segments, unfortunately I can't test it until tomorrow cause I miss some connectors. Anyway, how much do you think I will increase my coverage with my 5 segment collinear vs my 67 mm stock antenna?

    Here is a my antenna assembled
    Attachment 7580
    Hi

    Because I'planning doing one like yours, I would like to know how do you connected the antenna with the cable (to the dongle).
    Do you use a conector, if yes, how? Th Inner conductor of the antenna to the shield of conector and vice versa?
    Thanks
    Regards

  2. #172
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    Tried this project as my first wire collinear (see the scheme).
    I enclosed it inside a grey PVC plumbing tube (in the picture it is shown without it) and got quite disappointing results last night. After 30min testing I soon put my spider back again.
    Fyi my spider reaches 280nm from my actual position, somewhat amazing, but I hoped the collinear could give me ore range/gain.
    Instead I was getting 180nm
    Collinear-wire-adsb.gifIMG_20170507_163302.jpg
    Any suggestion?
    According to the guy who described that collinear, it should work like a charm...
    Today Im gonna make a Cantenna (66mm dia) and test it.
    Probably I will take a chance with a CoCo too.
    Last edited by perseus68; 2017-05-13 at 13:15.

  3. #173
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    Quote Originally Posted by perseus68 View Post
    Tried this project as my first wire collinear (see the scheme).
    I enclosed it inside a grey PVC plumbing tube (in the picture it is shown without it) and got quite disappointing results last night. After 30min testing I soon put my spider back again.
    Fyi my spider reaches 280nm from my actual position, somewhat amazing, but I hoped the collinear could give me ore rang/gain.
    Instead I was getting 180nm
    Collinear-wire-adsb.gifIMG_20170507_163302.jpg
    Any suggestion?
    According to the guy who described that collinear, it should work like a charm...
    Today Im gonna make a Cantenna (66mm dia) and test it.
    Probably I will take a chance with a CoCo too.
    Loops exactly those measurements? Its a super fussy design. mm accuracy type including the loop lenghts. Like, should be marked with 68mm and then meet at those points with no additional/missing
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

  4. #174
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    Also have a feeling my 2.0 I changed down to closer to 65mm which is nearer true 1/4 wave 1090mhz
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

  5. #175
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    Well, to be honest I built the coil by wrapping the wire around a 22mm dia support. This should give a 69mm length loop which is 1/4 lambda. I saw at least 3-4 schemes like that in the web and all of them do claim 5 dBi gain.
    I' m not sure about trying a second one at this point...

  6. #176
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    For a wire collinear try this

    All the technical stuff to me is unneccesary

    For my own antenna construction I use the simple formula
    300 divide by freq = full wave
    300 divided by 1090 = 275 mm

    so 1 wave = 275mm

    3/4 wave = 206.5 mm
    1/2 wave =137.5mm
    1/4 wave = 68.75 mm


    These are all the measurements you need

    Bottom of antenna -------/////--------------/////--------------/////--------------/////-------------- Top of antenna

    1st element = 68.75mm
    coil = 206.5mm of wire, wound into coil 68mm long
    2nd element = 137.5mm
    coil
    3rd element = 137.5mm
    coil
    4th element = 137.5mm

    Add as many elements / coils as you want
    If you put into a pvc pipe it will detune the antenna and it will be useless
    I




    Above antenna requires 1/4 w ground plane radials

    https://forum.flightradar24.com/atta...1&d=1383648542

    Name: ADSB ANTENNA.jpg
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    POST NO 830
    Last edited by YWYY; 2017-05-13 at 12:24.

  7. #177
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    Thanks YWYY.
    Sounds interesting.
    I do understand the first segment which is 1/4 lambda but then the coils are 1/4 wave or 68mm in "linear" length.
    The "physical" length of the coils wire is instead 3/4 wave or 206mm.
    It is unclear to me how you can phase a 1/2 lambda section with 1/4 lambda coil (or 3/4 long wire).
    If I look at the CoCo antenna it is composed by 1/2 lambda segments, all identical. There is no 1/4 lambda "phasing" in between them.
    Instead, the phasing stuff is 1/2 lambda and this makes sense to me.

    Definitely I need to study more about the antenna stuff.

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