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Thread: best antenna

  1. #1741
    Captain abcd567's Avatar
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    Quote Originally Posted by Marsmaensch View Post
    Hi ab cd,
    ..............tried to model it in 4nec2. however i could not find out how you modeled the coax (any tips on that, or some work i can use as a basis would be appreciated.)................

    ..........cant wait to have a look at your revised files ........

    Benjamin


    FOR USERS OF "4nec2" ANTENNA SIMULATION SOFTWARE:
    DOWNLOAD my two .nec files (Revised)

    CoCo made with RG6 cable (0.83 VF)

    Click the links below to download:

    (1) Revised file: Rev-variable length CoCo 4 element FPE insulated.zip
    (2) Revised file: Rev-variable length CoCo 8 element FPE insulated.zip


    Files were revised due to an error (the Velocity Factor VF was entered in column for Dielectric Constant k).


    How to add insulation to the core wire:




    NOTE:
    (1) To achieve accuracy, I have used small wire segments. This has resulted in large number of segments. Running "Calculate" takes several minutes. Running "Sweep" takes 15 min to 1/2 hr depending on your computer's processing power.

    (2) Ignore geometry error message (wires 1,2,3 & 4 "too thick").
    Last edited by abcd567; 2014-10-13 at 10:23.

  2. #1742
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    @gregy:
    @Marsmaensch:

    4-ELEMENT COCO
    After correcting the Dielectric Constant error in my .nec input files. I ran simulation of revised file for 4-ELEMENT CoCo, and results are astonishing:
    SWR is 5.03 at 114 mm length calculated by standard formula 1/2 Wavelength x VF.
    Minimum SWR (2.04) is at 102mm element length.




    Rev-SWR - Variable element length CoCo (4 elements) from RG6 VF 83 percent.PNG . Rev-GAIN - Variable element length CoCo (4 elements) from RG6 VF 83 percent.PNG . Rev-Gain Swr Pattern - 114mm element length CoCo (4 elements) from RG6 VF 83 percent.PNG
    Last edited by abcd567; 2014-10-13 at 13:37.

  3. #1743
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    @gregy:
    @Marsmaensch:

    8-ELEMENT COCO
    After correcting the Dielectric Constant error in my .nec input files. I ran simulation of revised file for 8-ELEMENT CoCo, and results are astonishing:
    SWR is 3.4 at 114 mm length calculated by standard formula 1/2 Wavelength x VF.
    Minimum SWR (1.18) is at 108mm element length.




    Rev-SWR - Variable element length CoCo (8 elements) from RG6 VF 83 percent.PNG . Rev-GAIN - Variable element length CoCo (8 elements) from RG6 VF 83 percent.PNG . Rev-Gain Swr Pattern - 114mm element length CoCo (8 elements) from RG6 VF 83 percent.PNG

  4. #1744
    Captain abcd567's Avatar
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    Quote Originally Posted by gregy View Post
    ......I will VNA sweep it and see if i can find clues .... .
    Quote Originally Posted by Marsmaensch View Post
    ........and drop by a friend with an antenna analyzer to validate the calculations.

    I am going to purchase This one when I get this one

  5. #1745
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    Quote Originally Posted by abcd567 View Post
    I am going to purchase This one when I get this one
    yes a friend with a VNA is a perfect friend!! partic if its a agilent, R&S or better!
    mine is very modest ... VNWA3 .... £400 ... but does the job for what i need

  6. #1746
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    Quote Originally Posted by gregy View Post
    yes a friend with a VNA is a perfect friend!! partic if its a agilent, R&S or better!
    mine is very modest ... VNWA3 .... £400 ... but does the job for what i need
    Yes, good VNA is on my wish list, but not the professional one for $ 150,000. Yours £400 seems reasonably priced for a (rich ) hobbyist.
    The one I linked, its name was originally HP (Hewlett Packard), then changed to Agilent, and now again recently changed to Keysight.

  7. #1747
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    @Trigger
    Hi Dave!
    Did you solve rain water/radome problem for your Franklin?
    See photos below how I solved it

    BEFORE I ATE THE RUSKS




    AFTER I ATE THEM ALL

  8. #1748
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    but did you attempt to determine the dielectric constant of bread rusks!
    "rusk tuning"?

  9. #1749
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    Quote Originally Posted by Marsmaensch View Post
    ...........i found that the shape and gain vary significantly with change in vf. is it possible for you to do a sweep in vf on your coco model?............
    Benjamin
    Yes it is possible to do a sweep with VF in my model.
    However, if you want to use coax other than RG6, then changing only VF in the RG6 model is not enough, as dia of insulation & dia of shield also change when type of cable is changed. This means re-modelling of the shield. The 4nec2 does not have provision for metallic sheet, and sheets are simulated by mesh of wires. changing the dia of shield requires complete re-modelling of the wire mesh cylinder used as shield.

    Please let me know specifically which cable/s you are interested in, so that I can re-model the nec input file accordingly, one separate file for each type of cable.

  10. #1750
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    @gregy:
    @Marsmaensch:

    4-ELEMENT COCO RG58 PE 0.66 VF
    I ran simulation of new file for 4-ELEMENT COCO RG58 PE 0.66 VF CoCo, and results are:
    SWR is 5.13 at 91 mm length calculated by standard formula 1/2 Wavelength x VF.
    Minimum SWR (3.12) is at 98mm element length.

    Download .nec file for this simulation:Rev-variable length CoCo 4 element RG58 PE insulated.zip

    Update Oct 15, 2014: Core insulation set to "Polyethylene" and .nec file above replaced by new one




    Rev-SWR - Variable element length CoCo (4 elements) from RG58 VF 66 percent.PNG . Rev-GAIN - Variable element length CoCo (4 elements) from RG58 VF 66 percent.PNG . Gain Swr Pattern - 118mm element length CoCo (4 elements) from RG58 VF 66 percent.PNG
    Last edited by abcd567; 2014-10-15 at 05:44.

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