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Thread: best antenna

  1. #1321
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    Quote Originally Posted by abcd567 View Post
    Now this is a conflicting situation. I get excellent results, while HermanZA gets not very good results. We need few more volunteers to run the test to be sure. Any volunteers?
    I'll try that new element lenght formula on my comparative test. It will take a while. The 4 element, shorted top (75 ohm resistor) test run finished yesterday. Now a 4 element, top open 1/4 whip test is ongoing.
    Northwest Spain: F-LECO1, F-LEST1

  2. #1322
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    Quote Originally Posted by Breitling View Post
    I'll try that new element lenght formula on my comparative test. It will take a while. The 4 element, shorted top (75 ohm resistor) test run finished yesterday. Now a 4 element, top open 1/4 whip test is ongoing.
    Thank you for your contribution & efforts.

  3. #1323
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    Quote Originally Posted by 1090 MHz View Post
    Like the one I built... 8 and a half elements was based on a HAM 70cm band antenna design.
    http://ads-b.ca/antenna-collinear-F-CYYZ2/img_9712.htm
    Your Antenna is excellent. You rightly call it "Super Antenna".
    Maybe the corrugated shape of the shield in Andrew-Heliax cable is a factor in it's excellent performance, as pointed out by SBSer in his post #1304

  4. #1324
    First officer 1090 MHz's Avatar
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    I have loads of the Andrew-Heliax LDF1-50 if anyone want some. They rewired the CYYZ 15L Glide-Path and this was the old cable. All of it was in good working order when removed from service.

    glidepath15L.jpg
    Photo courtesy Alex

  5. #1325
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    1090,
    Your 8 1/2 version... on the photo you posted, what infor and specs can you share on the 1/4 sleeve balun? What is your dimensions on the top element/section? Seem like 8 x 1/2 waves + 1 x 1/4 wave + protruding stub. you welcome to take this off forum, as I feel it might cause unwanted clutter. You can reach me on: fakm [@] eons [dot] co [dot] za

    ABCD,
    I will add another 2 elements to bring it to 8 in total. Current 6 element gives a meager 150km coverage. As it's currently at 5m above ground, I might be hitting the radio horizon (its not high up, as to have it easily accessible for modifications), that I base on the shape of the plot. Time to visit it again with a volt meter to test for shorts or bad connections, and add the elements.

    I'm thinking of doing another experiment:
    Use 1/2" copper tubing with a centre core of a copper rod, space the inner in the outer with rubber washers or a good dab of hot glue to keep the two parts evenly spaced and separated. Base it on ABCD's new dimensions, make it a 4 element. Thinking that having a more solid material (based on 1090's Super Antenna) will give better reception. Using this kind of material will result in a perfect straight antenna (no kinks due to soft cable). However, in a case like this, what VF should I assume to base the element lengths on?

    Looking at both ABCD and 1090's photo's, I can only assume I mess up at the very bottom of the antenna, as I construct the antenna elements, then directly insert the feed cable into the lower element, where both of you have either a balun or a short piece of cable followed by a connector and then the feedline.
    Last edited by HermanZA; 2014-07-24 at 08:59.

  6. #1326
    First officer 1090 MHz's Avatar
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    Quote Originally Posted by HermanZA View Post
    1090,
    Your 8 1/2 version... on the photo you posted, what infor and specs can you share on the 1/4 sleeve balun? What is your dimensions on the top element/section? Seem like 8 x 1/2 waves + 1 x 1/4 wave + protruding stub. you welcome to take this off forum, as I feel it might cause unwanted clutter. You can reach me on: fakm [at] eons .dot. co .dot. za
    http://ads-b.ca/antenna-collinear-F-CYYZ2/img_9685.htm
    The top is a 1/4 & 1/4 that's shorted at the center.

    http://ads-b.ca/antenna-collinear-F-CYYZ2/img_9719.htm
    The sleeve is made or 1/2 inch copper pipe.
    Since the antenna that was in this case before was a 2400 MHz I extended the sleeve to now match 1090 MHz
    Sleeve is none VF adjusted.

    The antenna was tested by a Nav Canada Engineer using their test equipment. He said the antenna peeked slightly above 1090 MHz but was so close it was within their standards and that he would certify it for an actual ATC use. The antennas bandwidth also extended it higher above 1100MHz making it also a good DME antenna.

    While we were at it we also tested the FR24 provided antenna and it also had good results but a wider bandwidth also including the 987 MHz UAT frequency.
    Last edited by 1090 MHz; 2014-07-24 at 09:16.

  7. #1327
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    Quote Originally Posted by HermanZA View Post
    ....Current 6 element gives a meager 150km coverage. As it's currently at 5m above ground, I might be hitting the radio horizon (its not high up, as to have it easily accessible for modifications), ...
    http://www.heywhatsthat.com/ in the air should give a good idea - i get a reasonable correspondence between what's theoretical from the map and what's measured (see the images in my sig)

  8. #1328
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    Quote Originally Posted by HermanZA View Post
    ......I'm thinking of doing another experiment:
    Use 1/2" copper tubing with a centre core of a copper rod, space the inner in the outer with rubber washers or a good dab of hot glue to keep the two parts evenly spaced and separated. Base it on ABCD's new dimensions, make it a 4 element. Thinking that having a more solid material (based on 1090's Super Antenna) will give better reception. Using this kind of material will result in a perfect straight antenna (no kinks due to soft cable). However, in a case like this, what VF should I assume to base the element lengths on?

    Looking at both ABCD and 1090's photo's, I can only assume I mess up at the very bottom of the antenna, as I construct the antenna elements, then directly insert the feed cable into the lower element, where both of you have either a balun or a short piece of cable followed by a connector and then the feedline.
    (1)With air insulation inside the tubing, VF = 1. Hence:
    element length (conventional formula) = 1/2 x wavelength x VF = 1/2 x 275 x 1 = 137.5 mm
    element length (new formula) = wavelength x VF/(1+VF) = 275 x 1/(1+1) = 275 x 1/2 = 137.5 mm

    (2) It is same weather the feeder is connected directly to bottom element of antenna, or through a short piece of cable with connector. I used short piece & connector only for the reason that I can easily interchange various antennas at connector point. All my antennas (all CoCos, Franklin, 1/2 wave dipole, & sleeved dipoles) have this short piece & connector. The connector & short piece are not part of antenna. These form part of the feed cable.

  9. #1329
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    Quote Originally Posted by abcd567 View Post
    Now this is a conflicting situation. I get excellent results, while HermanZA gets not very good results. We need few more volunteers to run the test to be sure. Any volunteers?
    I volunteer !!

    I made an 8 element coco today with 124mm segments. Results are not good, less than 50nm. However, I don't know what type of coax I have. It is stamped sat100 CE F.B.E. Neither the core or braid are magnetic. From previous experiments I think the coax is PTFE so I'll make another two at 109mm and 116mm.

    I'll be back in a couple of days.

  10. #1330
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    My current antenna testing setup is on the roof of my building at work. Only about 20feet high and severely obstructed to the north and east. But, it is an easy place to walk up to the reciever and swap out antenna.
    I have tried various designs of the coliniear antennas on this thread and have not gotten any of them to work any better than a 1/2 wave dipole.
    With the 1/2 wave I would get (from this location) reports from aircraft up to about 80 nm away and would regularly see 10 to 15 aircraft at a time during the day.

    Today I constructed a simple Jpole antenna and put it up. WOW! Consistently picking up planes 200 nm to the southwest .. and normally tracking 25 to 35 planes at a time.
    So far the J pole is the best antenna that I have tried. I guess after a few days trial on this... I will try making a Franklin or ZEP (modified J poles)
    Once the best antenna is built.. I can raise it up over most of the obstructions :-)

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