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Thread: best antenna

  1. #2731
    Captain abcd567's Avatar
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    Quote Originally Posted by mem0tap View Post
    Despite designing my own antennas I'm not an antenna expert, nobody is, it's a black art, guided by experience and a few rule of thumb calculations. I reckon for every successful antenna there's a few dozen in the bin!
    Fully agree

  2. #2732
    Captain abcd567's Avatar
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    Below are the simulation results for a CoCo (8-Elements, made of coax VF=0.86).
    These results show how a 1 or 2 mm error in element length can grossly affect SWR and Radiation pattern.
    Gain is relatively less affected by 1 or 2 mm error.

    The error in element length can either due to using wrong VF, or wrong cutting or a combination of both.

    In this simulation the a VF of 0.86 was used, giving element length 118 mm.


    SWR vs Element Length




    Gain vs Element Length




    Radiation Pattern vs Element Length





  3. #2733
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    Quote Originally Posted by abcd567 View Post
    Rooster:
    Attachment 9675 Attachment 9675 Attachment 9675
    Fully agree with you.

    Glad to see you after a long gap. Welcome back.
    Thanks mate - keep lurking, but not a lot has happened on here :-(

  4. #2734
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    Screenshot from 2018-07-20 23-06-53.png - results of my 'new' waterpipe antenna. fitted around midday Tuesday, it's mounted 7 feet below Jetvision antenna (which yields around 2400 a day, Since it looks promising I've upped the anti a touch and building an 8 section 22mm outer, 8.5mm inner air spaced.

  5. #2735
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    Got up on the roof today and relocated the FR24 antenna from its previous location on the side fence to above the TV antenna... now sitting about 1.2m above the highest point of the roof-line...
    (also solved a TV reception issue)
    FR24 antenna on roof.jpg

    (shot of previous location in this post https://forum.flightradar24.com/thre...l=1#post105113)
    Last edited by petercr; 2018-08-04 at 07:15.

  6. #2736
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    Horseshoe Antenna

    Found a very interesting horseshoe antenna made by galenthurber.
    Please see this thread


  7. #2737
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    SIMULATION OF HORSESHOE ANTENNA


    Gain = 3.2
    SWR = 3.5







  8. #2738
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    IMPEDANCE MATCHING STUB ADDED TO HORSESHOE ANTENNA

    Untested proposal. Expected to bring down SWR from 3.5 down to < 1.5


  9. #2739
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    Delved into this thread a few weeks ago, and started out with a cantenna for my first DIY antenna build. Surprisingly good results! Got about 160nm range from my south-facing apartment window.

    So, naturally I want to see how far I can take this project, so I tracked down some SO-239 connectors, and this past week I soldered together a 4-legged spider antenna (see attached photo - no idea how to rotate it, sorry!). Measured roughly, bent the wires haphazardly, and mounted it in PVC piping with tape on the brick outside the window. Seeing about a 10% increase in data from this antenna over the cantenna. Pretty cool! I have a few questions for anyone who cares to chime in:


    1. For someone who's new to antenna design and theory, how important is it that I seal/weatherproof the connection between the center wire and the SO-239 core element? I've seen mention of sealing, weatherproofing, and enclosing these antennas, but how important is it really?

    2. Would a more accurate measurement and completely straight wires help the antenna perform much better, or is that a nominal difference?

    3. Would soldering more wires on (say, 4 more to make it an 8-legged spider) make a big enough difference?

    4. Compared to those options above (improvements), would the better choice be to add an in-line amp?

    My apartment is up pretty high, but the antenna can only see South, East, and West. Almost zero north coverage due to the building and the mountains directly to my north.

    Thanks for the help!
    Attached Images Attached Images

  10. #2740
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    Quote Originally Posted by aesoprrp View Post
    1. For someone who's new to antenna design and theory, how important is it that I seal/weatherproof the connection between the center wire and the SO-239 core element? I've seen mention of sealing, weatherproofing, and enclosing these antennas, but how important is it really?
    It is not very essential. Lot of people use it without any sealing, weatherproofing, and enclosing.

    It works ok without sealing / water proofing. However after some period (say 1 to 3 years, depending on local weather conditions), rust & moisture set-in, and performance drops, or fails altogether.

    Applying water sealing increases the span of trouble free service.

    Quote Originally Posted by aesoprrp View Post
    2. Would a more accurate measurement and completely straight wires help the antenna perform much better, or is that a nominal difference?
    Depends how inaccurate it is initially. These antennas are very tolerant to dimensional errors, and will work OK even when built with an average skill. Making wire length, straightness of wires, and angle of bend more accurate may give an improvement of say 5% ~ 10% if it was originally build with an average skill.


    Quote Originally Posted by aesoprrp View Post
    3. Would soldering more wires on (say, 4 more to make it an 8-legged spider) make a big enough difference?
    It does make an appreciable difference, say 10% to 20%, but not a BIG difference.

    Quote Originally Posted by aesoprrp View Post
    4. Compared to those options above (improvements), would the better choice be to add an in-line amp?
    First you should try improving the antenna.
    After antenna improvement is done, then add an amplifier.
    Last edited by abcd567; 2019-01-19 at 18:30.

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