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Thread: best antenna

  1. #2321
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    Hi Guys, I'm using a 7dB Antenna with a magnetic base.It's sitting on an metallic plate mounted on a plastic pole.Do I need to use a metallic mounting pole to ground the base properly or will it lead to more noise?


    17221106405_79d3abbd64_o.jpg

  2. #2322
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    Quote Originally Posted by cloud_9 View Post
    Hi Guys, I'm using a 7dB Antenna with a magnetic base.It's sitting on an metallic plate mounted on a plastic pole.Do I need to use a metallic mounting pole to ground the base properly or will it lead to more noise?


    17221106405_79d3abbd64_o.jpg
    As this is designed for a car, the plate the magnet sticks to become the artificial Earth... you should really have a larger plate under it for this reason - it should reduce noise (as it will shield more of the world under it) the bigger the better really... but a biscuit tin lid would be a good starting point. (or similar size... maybe an old iron pan etc)

  3. #2323
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    Quote Originally Posted by Rooster View Post
    As this is designed for a car, the plate the magnet sticks to become the artificial Earth... you should really have a larger plate under it for this reason - it should reduce noise (as it will shield more of the world under it) the bigger the better really... but a biscuit tin lid would be a good starting point. (or similar size... maybe an old iron pan etc)
    Thanks mate!

  4. #2324
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    Hello guys I'm looking for some comments

    I've been running the dvb-t dongle with its standard antenna for a while now and got so-so performance. If I take FR24 reporting distance as a benchmark this would be 49 NM.
    Yesterday I decided to build a collinear antenna. I got a hold of some RG6 coax cable. Finding the correct building info was quite difficult I ended up with 10 elements of 116 mm.
    I haven't checked the math since I have no knowledge on this subject. After installing the cable I didn't receive the performance boost I hoped for.
    In the same benchmark FR24 now reports 55 NM after a half a day. But I do receive more aircraft. I know I haven't given the design much time but I have the "luxury" of living in a busy airspace.

    My situation is troubled by trees standing round my house, but the antenna is mounted outside in a pvc pipe. The USB dongle is mounted on the roof directly under the antenna.
    I was hoping you guys have any usefull tips for my improving my range!
    Naamloos.png
    range.png
    outer circle is 100 KM.

  5. #2325
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    How high is your antenna above ground? That is a critical factor, no matter how good or bad your antenna is. So try and give it more height, you will be surprised with better reception if you get it about 10m above ground. Or even on top of your roof even...
    Last edited by HermanZA; 2015-05-18 at 22:02.

  6. #2326
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    I'd guess the antenna starts at about 1 meter from the flat roof, my house itself is about 3 meters high. You can check the photograph to get an idea.
    I don't really want to put it any higher as its already standing out like a Christmas tree. I just expected better performance than the stock antenna...

  7. #2327
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    I would try a smaller antenna !!!!! Larger COCOs , if your maths + construction is NOT ACCURATE will only multiply the errors and produce an antenna with lousy performance.

    Larger antennae also drag in more interference, so you maybe overloading the dongle with signals you don't want.

    Try a simpler antenna "ABCD567's SPIDER" is a good start... place it in the same place as your COCO, on the same feeder and see how it goes.

    For measuring range, I use the RTL1090 software together with "virtual radar" this will map only what you see, and leave it running for 12 hours or so to create a decent map of your coverage.

  8. #2328
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    Quote Originally Posted by thebenchmark View Post
    I'd guess the antenna starts at about 1 meter from the flat roof, my house itself is about 3 meters high. You can check the photograph to get an idea.
    I don't really want to put it any higher as its already standing out like a Christmas tree. I just expected better performance than the stock antenna...
    I think Rooster's advice is valid. I made a collinear using the instructions in the following vid and came up with pretty good performance. Note the different length of the elements. Not all RG6 has the same velocity factor which can be a trap. I used 8 elements. Experimentation with the lengths seems to be an important aspect in hitting the 'sweet spot' for 1090MHz. You'll find a great deal of advice earlier on in this thread if you wish to persist with it.

    https://www.youtube.com/watch?v=TkUYdCPFXXs

    Regards,
    Gregg
    Last edited by fungus; 2015-05-18 at 22:29.
    YSSY2/T-YSSY4 [SBS-1 Basestation w/- SSE-1090 SJ Mk2 Antenna (Thanks Delcomp) ] [Uniden UBCD996T w/- 16 element Wideband Discone VHF/UHF Antenna, and tuned 108MHz-137MHz Airband Antenna] [Trialing a home-brew 1090MHz collinear antenna]

  9. #2329
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    Thanks for the replies, I'll order some parts and go for a spider and see how that works out. Could I just use 2,5mm² electrical cable for that? I got loads of that piling up here.

    One side question on the collinear if found some difference in designs on the web some people shorted their antenna, I found someone putting a resistor on and others made no contact, I went for the last. What's best?
    Concerning the maths I have no idea how that works, I got some length from our local coax broadband internet supplier so I thing the quality isn't lacking. It has a VF of 82% and an impedance of 75 Ohm.
    Also what kind of accuracy are we talking about? It was a very sturdy cable so I did have a mm of error here and there.

  10. #2330
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    thebenchmark,

    I added a quarter wave stub to the top of mine which seemed to help. Some bridge the top which would effectively make mine a 16 element antenna. I also made certain that all the elements were exactly the same length, to the mm. My 1090SSJ sits atop a 30ft mast on my ridge capping as height above surrounding obstacles makes the world of difference, not just with range but number of 'hits.'

    All I can suggest is to experiment and see what works for you.

    Regards,
    Gregg
    Last edited by fungus; 2015-05-19 at 14:01. Reason: additional info
    YSSY2/T-YSSY4 [SBS-1 Basestation w/- SSE-1090 SJ Mk2 Antenna (Thanks Delcomp) ] [Uniden UBCD996T w/- 16 element Wideband Discone VHF/UHF Antenna, and tuned 108MHz-137MHz Airband Antenna] [Trialing a home-brew 1090MHz collinear antenna]

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