Quarter wave vertical - Ground Mounted or Raised radials

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by G5TM, Nov 21, 2019.

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  1. G5TM

    G5TM Premium Subscriber QRZ Page

    Ok - 40m portable antenna - 1/4 wave.

    Can someone model the following and compare gain between:

    1. 1/4 wave ground mounted vertical for 40m with 80m in total of ground radials (8 x 1/4 wave)
    2. 1/4 wave vertical with 3 x 33ft radials around 2m (6 feet) above ground and running in a very slight angle to a support with their ends around 2-3 feet off the ground.

    I'd be interested to see the difference between that specific amount of ground radials (80m of radials selected bearing in mind the need to raise and remove the antenna each time you operate portable) and the raised radials.
    Thanks!
     
  2. WA4SIX

    WA4SIX Ham Member QRZ Page

    For the modelers, is it a true 1/4 wavelength?
    I think that the ends being 2'-3' off the ground may detune them a bit.
    For me, the difference being small, I would ground mount & lay radials. Time spent should be about the same.
    I do not model, as I am too fat.

    Ed
     
    VK6APZ, AK5B, KK4NSF and 2 others like this.
  3. WQ4G

    WQ4G Ham Member QRZ Page

    Last time I requested someone model an antenna for me here the only replies I got were from the crickets. Meaning none. Some times looking for help here on the Zed is counter productive.

    You might get more responses to your post if you would learn the software, model the antenna for yourself, and reply to your own posts. You'll probably get less blow back too... Some times the most innocent post, here on the Zed, provokes the ire of those with supposedly higher IQs.

    My experience, my opinion. YMMV....

    Dan WQ4G
     
  4. G5TM

    G5TM Premium Subscriber QRZ Page

    ooooooooook
     
  5. K7JOE

    K7JOE Ham Member QRZ Page

    Elevated radials are interesting. After doing a lot of reading in conjunction with building an elevated / inverted-L for 160m, here are a few things that i've recently learned.

    1) need to get them off the ground to avoid earth from de-tuning the radials.
    2) using elevated radials in pairs of two and tuned specifically for resonance (like a low dipole) is very important. So, go 2 or 4...
    3) a radiating element longer than 1/4 wave can allow use on other (harmonically related bands)...eg...rather than 1/4 wave, try a 3/8 wave wire for 40 ... it should work well with just a bit of base capacitance to work on 20M... etc.
    4) see this article for a method of using rope...to elevate the radials from the base if your antenna is ground mounted

    https://www.zl2al.com/1934/tuning-elevated-radials/
     
    Last edited: Nov 21, 2019
    WQ4G likes this.
  6. WA4SIX

    WA4SIX Ham Member QRZ Page

    Again, please provide the needed information for the modelers. Please include ground conductivity for your area (Google ground conductivity map). You just may be surprised.
    As a guess, you may have 1-3 db gain from mounting it above ground. 1/2 of an S unit (Using the generally agreed upon 6db per S unit)
    While this may be important for QRP, are the gains worth it in complexity of mounting?

    Ed
     
  7. WA7ARK

    WA7ARK Ham Member QRZ Page

    Click images to enlarge:

    G5rm1.png
    g5tm2.png
    G5tm3.png

    Black is 8 radials on ground; Blue is 3 (not very) elevated radials.

    The thing to look at is Average Gain.

    With either version, about half the transmitter power goes to warm the worms.
     
    Last edited: Nov 21, 2019
    G5TM, WQ4G and YF8RQN like this.
  8. W9XMT

    W9XMT Ham Member QRZ Page

    Below is an analysis of the 1/4WL 40m vertical with 8x10m radials lying on the surface of 5 mS/m, d.c. 13 Earth.

    This analysis was made using NEC4.2, which accurately models antenna conductors lying on, and/or buried in the Earth.

    Average gain for this model is 0.996, — nearly theoretical perfection. The model has no segment or geometry errors.

    [​IMG]
     
    WQ4G and YF8RQN like this.
  9. G5TM

    G5TM Premium Subscriber QRZ Page

    Thanks all .. appreciated
     
  10. W8EJO

    W8EJO Ham Member QRZ Page

    Why not try a vertical loop - no radials, better gain.
     

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