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Thread: best antenna

  1. #2751
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    Quote Originally Posted by abcd567 View Post
    Not necessay that every install gets 250+ nm. Only if no high rise building is obstructing the view of horizon, and antenna can "see" the horizon. .
    Totally understand. My maximum theoretical range is about 220nm depending on the direction. I live in a city very close to some mountains on two sides. So I get great range to the South and West (so far up to ~190nm with the various antennas I've tested, including the FA antenna), but less than 50nm to the North and East (unless the contact is very high, then maybe up to 80nm).

    I'll give that design a try this coming weekend!

  2. #2752
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    I've spent a lot of time experimenting with different antenna setups.
    This temporary arrangement is what I have currently:-
    1-ADSB antenna.jpg
    Mounted immediately above the ham radio beam is a glass fibre tube inside of which is a 16 element co-linear made from RG58 coax. That feeds a 15dB satellite amplifier which then goes down to my receiver. Above that is and 8 element co-linear made from RG59 coax in a polythene tube, fed directly at the moment via about 10 metres of RG59.
    Now clearly that diagonal feed cable coming from the to antenna can't stay like that. I've found that there is no benefit at all from the extra 8 elements or the amplifier - the biggest improvement by far has been from the height increase. So my intention is to remove the 16 element from the glass fibre tube and mount the 8 element antenna at the top of it and run the feeder neatly inside of it.
    I don't really want to have too many joins in the feeder cable so will probably re-construct the 8 element from fresh RG58 or RG59 and run the 12 metres required directly to the receiver.
    The cable loss at 1090Mhz is in the region of 5dB but as I'm running the receiver gain already at 8dB below maximum with the 10 metres of coax I don't see the need for adding the amplifier.
    Now, to get to the point! Designs for co-linear antennae are easy to find on the internet and I have made several. The difficulty is comparing results of the different designs without the option of running tests simultaneously. I prefer to solder the joints so that rules out the push together and tape designs. I have't found any benefit from using the heavier RG6 or RG8 so will stick to either RG58 or RG59. As I'm via feeding the latest Flightaware filter it would seem logical to 50 Ohm RG58 coax.
    Can anyone answers these questions then please:-
    1: Co-linear elements RG58 or RG59.
    2: Above the 8 half-wave elements, a quarter-wave rod, nothing, a 50 or 75 Ohm resistor.
    2: How important are a matching sleeve and ferrite rings at the bottom.
    4: Would quarter wave radials at the feed point make any difference.

    T-EGSY73

  3. #2753
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    A general purpose amplifier is not necessarily beneficial.

    LNAs with filtering builtin are much better:
    https://www.rtl-sdr.com/new-product-...mhz-ads-b-lna/

    Much better filtering than the FA filter and the blue pro stick.
    Goes best with one of the v3 dongles they offer, they are good quality.

    Above the 8 elements it doesn't matter much what you have as most of the signal gets radiated by the antenna before making it to the feed line.
    Also the reason why adding more elements doesn't change that much.
    It does slightly improve rejection against other frequencies and somewhat changes the gain profile to be even flatter.

    Quarter wave radials seem rather impractical.
    Not sure if you really need a matching sleeve/ ferrite.

    But if you are thinking about that then i would rather eliminate the 5dB attenuation from the cable you mention.
    While you might run attenuation in the receiver the stronger signal in the cable/ connection to the receiver reduces the influence of possible noise.
    The point in the receiver where the signal is attenuated is very close to where it is actually converted/sampled.
    That minimizes possible signal disturbances.
    Last edited by wiedehopf; 2019-02-28 at 05:58.

  4. #2754
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    Thanks for that.
    This is the amplifier I tried https://www.ebay.co.uk/itm/231361695425, mainly because I was splitting the antenna feed passively to 3 different receivers so was losing another 6 dB in the process.
    I have a blue Flightaware filtered dongle, a yellow Flightaware dongle with the latest filter in front of it and a very cheap Ebay dongle.
    It looks like I've reached the peak effectiveness now at this location with the orange stick/filter combination, although I may try putting the external filter in front of the internally filtered blue dongle.
    Peak range is 349 nm, average 214 nm (still rising a little) On a good day I'm getting 1.8 million hits from 3000 aircraft. That compares to 2400 aircraft and 1.4 million hits with the un-filtered cheap Ebay setup.
    Another option of course is to have the dongle right up at the antenna on a long active usb cable, but I doubt the improvement is worth that effort.
    I'm never going to get to this level! https://www.flightradar24.com/accoun...stats/?id=9096 - where on earth are all those aircraft coming from over the UK?
    Last edited by Scroggie; 2019-02-28 at 20:00.

  5. #2755
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    @Scroggie:

    Your satellite amplifier remind me of my original setup in 2013 (see 2 photos in the post below)


    Post #68 dated 15 Sept 2013

    .

  6. #2756
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    Those stats you linked just look bogus in regards to the aircraft count.

    Right in this subforum is also the "What is my maximum range thread?", have you looked at that?

    Anyway the maximum number of aircraft you have probably reached but if you want to get more messages you need to go to the likes of an airspy mini or a mode s beast.
    Both aren't quite as affordable as the dongles you have.
    And the airspy mini would be a waste without a filtered LNA.
    Last edited by wiedehopf; 2019-02-28 at 22:40.

  7. #2757
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    Quote Originally Posted by Scroggie View Post
    I'm never going to get to this level! https://www.flightradar24.com/accoun...stats/?id=9096 - where on earth are all those aircraft coming from over the UK?
    Simply put, they’re not, this is a good example of a ‘T’ feeder who is spoofing his feed, the great majority of his ‘hits’ are from less than 100nm, I have what I consider to be good coverage and am close to both Heathrow and Gatwick but only get around 1/10th of what he claims! Also as he is (or claims to be) in Kent he appears to have poor coverage to the west, so he would be missing most of the London traffic! I suspect he is feeding from a mash up of different data sources and it is probably mostly garbage.
    FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

  8. #2758
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    Quote Originally Posted by F-EGLF1 View Post
    Simply put, they’re not, this is a good example of a ‘T’ feeder who is spoofing his feed, the great majority of his ‘hits’ are from less than 100nm, I have what I consider to be good coverage and am close to both Heathrow and Gatwick but only get around 1/10th of what he claims! Also as he is (or claims to be) in Kent he appears to have poor coverage to the west, so he would be missing most of the London traffic! I suspect he is feeding from a mash up of different data sources and it is probably mostly garbage.


    Yes - looks like it doesn't it.

  9. #2759
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    @abcd567:

    I've spend today constructing another coaxial co-linear - 12 elements this time.
    I found your excellent posts on the other forum detailing all the tests you did on this type of antenna.
    The weather here is currently very stormy and it will be days before I can get this up to a useful height to test it properly and I would appreciate a bit of advice before I finalise and erect it
    .
    There are several designs to be found when internet searching but it's not really clear which is the most effective.
    I see from your tests that a 12 element has a feed impedance of 62 ohms so looks likely to be the best choice.
    I have made 6 or 7 of these so far, 8 and 16 elements and they have all seemed pretty good and very similar in performance.

    I just wonder what the best arrangement is at the top. I've tried a quarter wave rod, nothing, and a 75 ohm resistor.
    I've tried with a quarter wave sleeve at the feed point and without.
    This 12 element I've made today is using RG59 and has a 75 ohm resistor at the top. I chose RG59 because I happened to have a reel of it. I have the latest Flightaware filter and intend to have that up at the feed point feeding a satellite amplifier which will then have 40 feet of RG59 into the house. I have gain to spare in the dongles so I could dispense with the amplifier but having it gives me the opportunity to feed 3 dongles (Flightaware Blue, Orange and cheap eBay) through a splitter (which gives a 6 dB loss at each outlet)
    I'm assuming that having very short connections from the antenna to the filter and then to the amplifier will make impedance mismatches less important. The amp has a 75 ohm output impedance, perfect for the RG59 it is feeding.

  10. #2760
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    Hi @abcd567! Still testing antennas? I have recently tested an interesting design of my own and need somebody experienced to build a replica and test against already tested solutions. If you are interested, please contact me at oh6my@sral.fi and ask for pictures of the design.
    -Hans
    Last edited by HAm; 2019-10-09 at 18:36. Reason: typo

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