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  • petercr
    replied
    Makes an interesting alternative to electrical conduit that I had my previous CoCo installed in...

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  • mem0tap
    replied
    Ok, I looked at the design of several Coaxial co-linears and decided I'd have a go at building my own. Based on my knowledge of Satellite systems and knowing the larger the area of the dish the more sensitive it is to weaker signals, I thought I'd try something with a little more surface area. Secondly because of the 'skin effect' at 1090 Mhz, I'm not convinced coax is an ideal medium for the Job.
    After some calculations I arrived at using 18 guage Tinned copper wire for an inner and 15mm copper water pipe as the outer. Whilst pottering around in the garden I hit upon the idea of using bamboo cane as the dielectric, after all it's a very dry, and has a rather convenient hollowness about it. - Here are pictures of the prototype, which is working rather well and outperforming a Jetvision antenna mounted some 7 feet higher up!CIMG3757.jpgCIMG3758.jpgCIMG3759.jpgCIMG3760.jpg Characteristic Impedance 45.7ohms - feeder 50ohms, next step to build the filter and dongle inside with the antenna, I have tested a 10metre proprietary USB2 extension lead (with built in buffer) and it works fine with a respberry PI - looking at using 1" copper pipe and a more efficient spacer for the Mkii!.
    Last edited by mem0tap; 2018-07-16, 22:52. Reason: further data appended,

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  • Coxy
    replied
    I am using two spiders, one which just uses the coax with the legs pushed into the shield and the other is using a S0-239,PI-259 setup. Both are as effective as the other. The cantenna was great as well but a little less range the the spiders.

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  • abcd567
    replied
    @Oblivian
    Thank you so much for using your Super Moderator authority to change/shorten the thread title.
    The title now sounds much better.

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  • Oblivian
    replied
    Originally posted by abcd567 View Post
    Immediately after creation of FR24 thread, I realized that its title is too long, and wanted to modify it to the shorter name "Do I Need A Filter?", but the FR24 forum does not allow to change thread title once it is created.
    ... https://forum.flightradar24.com/thre...ignals-In-Area

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  • abcd567
    replied
    Originally posted by petercr View Post
    During the week I ran the 'do I need a filter' test .....
    In October & November 2017, I created two identical threads describing method for RF Scan as listed below:

    28 October 2017 - FlightRadar24 forum, Titled: Find Out Existing RF Signals (Cell/Mobile/Pager etc) In Your Area

    09 November 2017 - FlightAware forum, Titled : Do I Need A Filter?

    Immediately after creation of FR24 thread, I realized that its title is too long, and wanted to modify it to the shorter name "Do I Need A Filter?", but the FR24 forum does not allow to change thread title once it is created.

    Few days later when I created the same thread in FlightAware forum, I used the short and handy name "Do I Need A Filter?"
    Last edited by abcd567; 2018-05-19, 22:33.

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  • Ubbe
    replied
    About DC blocker: Or you could open up the amp, the lid is often just a very thin metal plate with press fit, and remove the power pass coil that are easily spotted as it goes from input to output and are usually the only component that are placed on the circuit board on the lid side.

    Remember that those sat amplifiers could have a noise figure of 5dB and the generic 50-3000MHz $25 amplifiers from Ebay have 0.8dB or even less. You can dig up more signals 4dB down in the noise with those low noise amplifiers. It's like you had doubled the gain of your antenna.
    Last edited by Ubbe; 2018-05-19, 20:23.

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  • Stealth
    replied
    Originally posted by petercr View Post
    Went and bit the bullet and ordered an FA antenna and set it up last weekend replacing the old 8-element CoCo;

    [ATTACH=CONFIG]9463[/ATTACH]

    It's now running 'naked' (ie no amp which was in that piece of pipe you can see on the fence) into a FA Prostick+. I'm now getting regular hits 200Nm+ and yesterday set a new bench-mark of 224Nm to the NE out over the Coral Sea.

    The mast consists of a 1.8m J-bracket (designed for mounting TV antennas) sitting 1.7m above the ground to which I've added an old pool cleaner pole which adds another 3.8m on with the antenna clearing the house roof-line.

    During the week I ran the 'do I need a filter' test and there's spikes from the not-too-far distance GSM tower
    [ATTACH=CONFIG]9465[/ATTACH]
    so I've ordered a filter from Hungary via eBay and it should be here in a week or so. I'll test it locating it up top of the antenna and also just before the Prostick to see if there's any discernible difference.
    Good to hear its worked well for you. It still leaves some room to experiment, so win-win!

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  • petercr
    replied
    Went and bit the bullet and ordered an FA antenna and set it up last weekend replacing the old 8-element CoCo;

    Antenna.png

    It's now running 'naked' (ie no amp which was in that piece of pipe you can see on the fence) into a FA Prostick+. I'm now getting regular hits 200Nm+ and yesterday set a new bench-mark of 224Nm to the NE out over the Coral Sea.

    The mast consists of a 1.8m J-bracket (designed for mounting TV antennas) sitting 1.7m above the ground to which I've added an old pool cleaner pole which adds another 3.8m on with the antenna clearing the house roof-line.

    During the week I ran the 'do I need a filter' test and there's large spikes from the not-too-far distance GSM tower (about 1km away slightly to the right of that tree)
    1090Mhz waterfall and spectrum.jpg
    so I've ordered a filter from Hungary via eBay and it should be here in a week or so.
    https://www.ebay.com.au/itm/ADSB-Fil...53.m1438.l2649
    I'll test it locating it up top of the antenna and also just before the Prostick to see if there's any discernible difference.
    Last edited by petercr; 2018-05-19, 10:46.

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  • Stealth
    replied
    @abcd567

    Maybe I didn't convey in that post that I'm on top of the basics.

    The point of the post was to relate how dramatic the effect of signal overload can be. It wasn't just a reduction in displayed aircraft or range, it was a drop from seeing numerous aircraft, some beyond 175nm to seeing virtually nothing. Virtually nothing was just one aircraft within about 15nm. It was way more dramatic an effect than I would have imagined.

    Some additional learning points from this scenario were:

    + Don't assume an antenna is going to work well solely based on reflected power reading i.e. VSWR, however its a good sign that it will work to some degree
    + Range should not be used as the sole indication of antenna effectiveness, look at message rate and the number of 'hits' over a significant period of time
    + Finally, don't ever take something at face value, check it out

    My 'fall back' and the 3 element co-linear I mentioned previously are shown below (original graphics as downloaded, not my actual versions).

    150_x_150 colinear.jpg

    5-8th.jpg

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  • abcd567
    replied
    @Stealth

    I suspect your "fall-back antenna" is a low gain simple antenna like the mag-mount Whip (supplied with dvb-t), or Spider or Cantenna. These simple antennas pick comparatively less cell/mobile signals, and the 1090 mhz signal is not "drowned" into the strong cell/mobile signals.



    Below is the RF Scan of signals at my location showing strong Cell Phone signals.

    The scan was done using OPTION-2 (DVB-T plugged into Windows computer) of following thread:

    Find Out Existing RF Signals (Cell/Mobile/Pager etc) In Your Area

    Last edited by abcd567; 2018-05-19, 17:41. Reason: Fixed broken image of scan

    Leave a comment:


  • Stealth
    replied
    Playing with antennas is the best part of this pursuit. Last week I was about to build my third co-co in recent times, first two were duds. No matter what I did with them the analyzer kept showing a low VSWR everywhere but 1090. So for a change I built a three element co-linear using coax screen and built on a 6mm fiberglass rod, three simple coils and all was ready to go. Analyzer showed around 1.6 VSWR. Down with the mast, up with the antenna. Rush indoors to see results.......nothing, blank screen.

    Back to the fall-back antenna and a re-think. Decided to get a FA antenna express mailed, just to give me a commercial benchmark. Arrived today, wait for the wind to die down and up it goes. Expecting glorious signals, hurry inside. One measly signal within 20 nm, nothing else.

    Much head scratching, try a few changes on the gain settings and two or three signals close in. I wonder, so drag out the bandpass filter and insert. Bingo! Signals flooding in and at a very decent rate. The FA antenna had brought enough signal in to completely overload the FA Pro-stick Plus.

    Now I wonder if my co-linear from last week was good after all and I had the same issue........

    I should mention that the 'fall-back' antenna had been receiving quite well, worst was out to 100nm best out to 200nm + in some directions.
    Last edited by Stealth; 2018-03-20, 12:50.

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  • abcd567
    replied
    CONGRATULATIONS!

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  • petercr
    replied
    Looks like the new antenna is working based on the last 7 days...
    new antenna.png
    (and today is only just 4hrs old based on GMT)

    max range last night was 145Nm

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  • abcd567
    replied
    Great to know you already have experiance in DIY antennas by helping your dad, an amateur radio enthusiast.

    Yes, DIY is cheaper for sure . This is in addition to the fun and satisfaction it gives.

    Leave a comment:

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