Page 230 of 285 FirstFirst ... 130180220228229230231232240280 ... LastLast
Results 2,291 to 2,300 of 2848

Thread: best antenna

  1. #2291
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,882
    @JLD:
    @SpaxmoidJAm:
    @F-EGLF1:
    Simulation of JLD's Thick-Thin wire Collinear (by software 4nec2) :


    Have a look at the radiation pattern at right side of screenshot

    Thick Thin Collinear Monopole Short Feed+Groundplane.PNG
    Last edited by abcd567; 2015-04-06 at 17:05.

  2. #2292
    Passenger
    Join Date
    Feb 2015
    Posts
    14
    The length of the elements change with wire/tube diameter (larger diameter wires resonate at a frequency lower than their physical length).
    I use 4 ground plane 65mm 2.5mm dia
    first vertical 1/4 wave: 61 mm 10mm dia tube
    half wave phasing line: 138mm 0.1mm dia wire
    half wave radiating tube: 122 10mm dia tube
    the ground plane wires are around 60 deg from vertical for 50 Ohms and 35 deg from vertical for 75 Ohms.
    return loss is around 20 dB and SWR better than 1.5.

    I have no way to measure radiation pattern.
    It is not as good as the 8 elements co linear I already build but this was not supposed to!
    I will build a small ground plane as a reference antenna and comapre the number of messages I get.

    JL

  3. #2293
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,882
    @JLD:
    Thanks for the details of dimensions. I will modify my model accordingly, re-simulate, and post the results.

  4. #2294
    Passenger
    Join Date
    Mar 2015
    Posts
    3
    abcd, what does your software suggest for the performance of that franklin/spider hybrid? It looks like it might be worth a try.

  5. #2295
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,882
    Quote Originally Posted by caius View Post
    abcd, what does your software suggest for the performance of that franklin/spider hybrid? It looks like it might be worth a try.
    I did not run a simulatuon for it as I had little hope of it's success. I just put is as a concept, as an analogy to JLD's proposal.

  6. #2296
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,882
    @JLD:

    Simulation using dimensions provided by you - slightly improved radiation pattern, but not much different.

    JLD Thick Thin Collinear Monopole Short Feed+Groundplane.PNG
    Last edited by abcd567; 2015-04-07 at 06:19.

  7. #2297
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,882
    Quote Originally Posted by caius View Post
    abcd, what does your software suggest for the performance of that franklin/spider hybrid? It looks like it might be worth a try.
    MY NEW DESIGN:
    HYBRID OF FRANKLIN & SPIDER



    FRANKLIN-SPIDER
    Gain = 4.14 dBi
    SWR = 2.09


    Franklin Spider.PNG



    SPIDER
    Gain = 2.08 dBi
    SWR = 1.97


    Spider.PNG




    Based on my above design, an antenna was built by forum member xforce30164, and is on trial run now:

    http://forum.planefinder.net/threads...na.23/page-131

    IMG_20150407_202113_1428430883242.jpg
    Last edited by abcd567; 2015-04-08 at 07:16.

  8. #2298
    Passenger
    Join Date
    Feb 2015
    Posts
    14
    Interesting!
    The results of the thick/thin co-linear don't match the results I get with the real antenna, at least from an impedance stand point.
    Also the gain you find would be fantastic if it was true: 16 dBi at 90°!
    I am afraid that for some reasons, 4nec2 does not do a good job here.

    In the other designs, with 2mm wires, you should use 65mm for 1/4 wave and 130mm for 1/2 wave.
    Using 69 and 138 probably give you an antenna with a resonance at 1040 Mhz.

  9. #2299
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,882
    Quote Originally Posted by JLD View Post
    Interesting!
    The results of the thick/thin co-linear don't match the results I get with the real antenna, at least from an impedance stand point.
    Also the gain you find would be fantastic if it was true: 16 dBi at 90°!
    I am afraid that for some reasons, 4nec2 does not do a good job here.
    ....snip...
    Yes, in some cases the 4nec2 software does give erroneous results, but we never know how it will behave in a particular case. In fact it has put me in an embarassing situation several times due to erroneous results.

    For this reason, after simulation, I always make a prototype and put it to trial run. Unfortunately I dont have access to VNA and other test equipment to conduct a laboratory test. I therefore put my prototype directly in operation and compare ttheir results with my benchmark antenna.

    Can you please post the photos of your antenna, and maximum range plot? I use VRS (virtual radar server) software or adsbScop software to plot maximum range over a period of at least 24 hrs.

    The ONLY piece of test equipment I have
    MJCA-211.JPG.jpeg
    Last edited by abcd567; 2015-04-08 at 07:32.

  10. #2300
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,882
    Quote Originally Posted by JLD View Post
    ...snip....
    In the other designs, with 2mm wires, you should use 65mm for 1/4 wave and 130mm for 1/2 wave.
    Using 69 and 138 probably give you an antenna with a resonance at 1040 Mhz.
    Thanks for key information about dimensions. I will keep these figures in mind when designing/simulating antennas

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •