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Thread: Aussie Feeders

  1. #711
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    Quote Originally Posted by bhaal View Post
    Ohhhh, didn't know they had a pre-amp .. I was of the understanding that would just amplify the noise if it's at the end of the cable?
    Yes, it does amplify signal and noise, the best spot for any amp is at the base of the antenna to maximise effect, it of course will amplify from device end, but not as effectively.

    I have a 20 mtr active USB lead, one day I'ma gunna "tape" the dongle and its own antenna to the existing pvc ant, and see what improvements I get I have 15 mtrs of RG6, although its loss characteristics are not as bad as if this were for vhf/uhf comms band, its still a bit lossy, just how much , who knows.

  2. #712
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    Quote Originally Posted by bhaal View Post
    YSWG .. Is it possible to put the FR24 antenna on the RTL dongle and vice versa? That would be a good test...
    considering the dongle is 75 ohm, and the fr24 box is 50 ohm, it would work, but I suspect not very well.

  3. #713
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    Quote Originally Posted by Ressy View Post
    Yes, it does amplify signal and noise, the best spot for any amp is at the base of the antenna to maximise effect, it of course will amplify from device end, but not as effectively.

    I have a 20 mtr active USB lead, one day I'ma gunna "tape" the dongle and its own antenna to the existing pvc ant, and see what improvements I get I have 15 mtrs of RG6, although its loss characteristics are not as bad as if this were for vhf/uhf comms band, its still a bit lossy, just how much , who knows.
    Ahhhh, I *could* pre-amp but I have the feeling it might overdrive the dongle, considering the Pi is at the end of a 1mtr piece of coax at the base of the mast.. I have the Pi running via PoE, the same as I have done for the other 3 Pi's up the top of that mast...

  4. #714
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    Quote Originally Posted by Ressy View Post
    considering the dongle is 75 ohm, and the fr24 box is 50 ohm, it would work, but I suspect not very well.
    Hmmm, my dongle which I got from Adafruit has a 50 ohm input, so for me that wouldn't be an issue... (I have a 30cm pigtail of the original 50ohm coax from the little internal magnetic antenna so that its not 75ohm being shunted straight into the dongle)...

  5. #715
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    Quote Originally Posted by bhaal View Post
    YSWG .. Is it possible to put the FR24 antenna on the RTL dongle and vice versa? That would be a good test...
    Negative, would need to get an MCX/SMA adapter and would need to take the FR24 box off the air for a significant amount of time, which is not possible.

    I want to get 10m of LMR400 and the same/similar antenna but not going to happen in the short term (Avalon and Uni are around the corner).

    Should give you a better idea without aircraft.
    IMG_20150126_233954.jpg

  6. #716
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    Quote Originally Posted by YSWG View Post
    Negative, would need to get an MCX/SMA adapter and would need to take the FR24 box off the air for a significant amount of time, which is not possible.

    I want to get 10m of LMR400 and the same/similar antenna but not going to happen in the short term (Avalon and Uni are around the corner).

    Should give you a better idea without aircraft.
    IMG_20150126_233954.jpg
    What size are your range circles?

  7. #717
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    9 rings every 50 km

  8. #718
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    Here are my results with the FR24 hardware vs my USB dongle. The rings are 50 km apart - same as YSWG's - with the outermost ring being 450 km. The USB stick has a DIY dipole antenna and is on the same mast as the FR24 antenna.
    usbvsfr24.png

    Where the FR24 setup has a particularly large gain compared with the USB stick is where LoS is obstructed (namely, around 0 to 135 degrees).

    Ignore that line straight out east - it was caused by a LAN flight (CC-CQC) sending out spurious ADS-B locations.

  9. #719
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    Quote Originally Posted by eastons View Post

    "Ignore that line straight out east - it was caused by a LAN flight (CC-CQC) sending out spurious ADS-B locations."
    eastons,

    I'm staggered that they haven't chipped LAN over their spurious ADS-B longitude signals as it has been occurring for years. I've had discussions with Air Services Australia about them. A number of their aircraft have been doing so (I've had them out to 14,000 miles or so at times on my SBS Basestation) and I would have expected that since the introduction of compulsory equipping/usage of this technology here in Australia above FL290 that they would have been forced to comply. I think they are planning to drop the route, or at least change the aircraft type soon (787?) so that may fix the problem.

    ... and my plot isn't quite as good range wise as that one of yours and in some directions a bit more patchy, but not by very much. I can reach the Victorian border at times (and past it on rare occasions depending on weather conditions, but mostly only 'spots'). East, and South East is knackered due to the city etc but most other directions similar as yours. My 'night vision' is also better than during the day but I rarely run the unit then. I live in 'Frog's Hollow'

    PLOTTER4.jpg

    Regards,
    Gregg
    Last edited by fungus; 2015-01-27 at 04:07.
    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]

  10. #720
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    I have used the FR24 antenna with the dongle and it doesn't receive the same number of decoded messages. I get a similar range with either the FR24 antenna or my cantenna using the dongle. The antennas are the same height.

    When I put the cantenna on the FR24 receiver i also get a similar range to the dongle - just a lot more decoded messages.

    Obviously the FR24 receiver and the FR24 antenna are closely matched and achieve pretty close to optimal perfomance.
    Last edited by stanno; 2015-01-27 at 04:07. Reason: context

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