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Thread: Home Brew Antenna

  1. #1
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    Home Brew Antenna

    I have often wondered about making or buying a 'better' antenna and putting it outside but because of where I live, I don't know whether it would make much difference. My house is in the middle of a housing estate near the top of a hill and although there's a clear view of the sky to the North, there are houses slightly higher than mine that partly obscure our view of the sky to the South.

    I made a few antennas of different designs and spent ages tweaking and moving them around in the loft to get the best signal. The one I am currently using is a rather crude homemade ground plane type, which sits in the centre line of the roof right up under the ridge tiles.

    I currently get an average of about 80 NM and, unfortunately, very little of that is from lower than about 10000 feet in any direction.

    For mobile use, I use an equally crude homemade full wave dipole, which I plug straight into another tv stick.

    What seems odd to me is that, if I sit in my bedroom with my laptop with the dipole plugged into the tv stick I get only slightly fewer planes than the RPI gets with the loft antenna. However, when I replaced the dipole type that was originally in the loft with the ground plane one, the difference was like night and day.

    Anyone have any thoughts about what I can do to improve things (apart from moving)?

  2. #2
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    You can check how much better your reception could be by taking your laptop and climbing onto the roof

    You can also check this: https://forum.flightradar24.com/thre...ange-I-can-Get

    Could well be that the loft has insulation which shields signals.

  3. #3
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    Yes, I read that article the other day and found it very informative.

    Unfortunately, putting an antenna on my roof is a bit awkward: I have a tall pole with a high gain TV aerial on the gable wall one end which required scaffolding to erect due to the narrow path next to the house. The other end is equally awkward to access because of the attached garage. So I think it has to stay in the loft.

    I had a look at the roofing felt and it doesn't have a foil backing on it.

    What I really wondered was whether any of the pukka antennas you see for sale would improve my signal strength. I am quite prepared to be corrected but I assume that an amplifier and/or filter probably wouldn't help.

  4. #4
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    If you don't mind spending around 100$ the best gear you can probably get for the dollar in my opinion is this:
    https://www.rtl-sdr.com/new-product-...mhz-ads-b-lna/
    That goes well with their v3 dongle because it has a builtin bias-t for supplying the LNA: https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/

    A commercial antenna is beneficial in the loft as well. The Flightaware antenna is probably a good improvement no matter if you go with the LNA above.
    (If you manage to build a good colinear that is an option as well, but it seems hit and miss)

    How much of an improvement all of this will bring depends on the obstacles.
    You surely won't get beyond the outline shown on heywhatsthat.com for your location with UpIntheAir set at 40000 ft.

    But you might get reception in the direction where other houses are in the way, not sure how much though.

    What's a pukka antenna?

    So i guess that also means you can't access that pretty mast you already have with a ladder, huh?

  5. #5
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    By pukka, I meant commercially made rather than home brew.

    Problem is that asking about which antenna or stick to buy on forums is rather like discussing football or religion in a pub - ask a dozen people and get a dozen different answers. Always assuming you don't get severely injured in the ensuing fight of course.

    The stuff from rtl-sdr looks interesting and I guess I could always sell it on if it doesn't help.

    Would the RPI be able to supply enough power for the dongle and the LNA or would an in-line bias tee be better?

    I tried building a colinear when I got into this back in 2015 but couldn't get a decent signal with it (them).

    I had a look at heywhatsthat the other day and that is also useful but I kind of knew where my problems were before hand.

    I also ran up SDR again to see if there was nay significant interference that wasn't there before and it looks OK to me.

    I had to get someone out to adjust my TV aerial when it got moved in the wind quite a few years ago and every one of the people I contacted said they wouldn't do it without putting up scaffolding. That was about £150 too much for me so I collared a guy who was walking up some one else's roof down the road (obviously hadn't heard of health and safety) a few weeks later and he did it for £30. Thank you very much I said.

    Not much chance of that nowadays.

  6. #6
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    If you have a decent power supply for you RPi it shouldn't be a problem.

    You have to do some wrangling to turn on the bias-t though: https://forum.flightradar24.com/thre...l=1#post104715

    You can also buy the uputronics LNA that can be supplied via USB, the performance should be about the same. (i have never tried the uputronics but i like the dual stage triple filter design of the rtl-sdr better)

    I think everyone who has used one of those two external LNAs will tell you that they are better than the ProStick Plus (which has an internal LNA).
    You could also use the uputronics LNA with the receiver/dongle you currently use or even the rlt-sdr LNA with a separate bias-t.
    (I like the metal enclosure of the rtl-sdr v3 and i just believe in their design)

    With antennas i believe pretty much every other antenna is more expensive compared to the Flightaware antenna.

    I personally use a simple ground plane quarter wave with 8 radials mounted on the chimney.
    So the LNA on its own is very nice, i would probably recommend that thing above all else.

    Offsetting the loss due to the roof with a commercial antenna can't hurt though.
    Last edited by wiedehopf; 2019-04-12 at 17:05.

  7. #7
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    Wish I had a chimney.

    Wish I lived on the top of the hill.

    Wish I had more money.

  8. #8
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    Did you try less than £1, made of 1m piece of coax, Quick Spider?

    EASY ANTENNA # 3 : QUICK SPIDER - No Soldering, No Connector Required

  9. #9
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    That is more-or-less what I currently have in my loft. It was the one that performed the best out of all the types I made.

    Here's something I have wondered about for a while: Would it be possible to have two antenna (one on a pole at the front of the house and one on a pole at the back of the house) each feeding their own receiver and aggregate the data with something like modes2deco?


    Would I just end up with a data mess that can't be unravelled?

  10. #10
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    If you disable MLAT feeding or only use the data for local display it's not a problem.

    You can use this: https://github.com/wiedehopf/combine1090#combine1090

    Normally it's output port is disabled, but you can enable it by changing --net-bo-port 0 to 29999 for example.
    That's where you can point beast-tcp of fr24feed to for example.

    It's for dump1090-fa but that's easy enough to install.
    Last edited by wiedehopf; 2019-04-13 at 11:23.

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