Radials and hard ground?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KI6BCX, Apr 5, 2011.

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  1. KI6BCX

    KI6BCX Ham Member QRZ Page

    OK, this year long project has its end in sight... The evil HOA has been defeated, the wife is happy with the new location, and the pvc conduit for the coax run has been laid.

    The big issue now is laying the radials. The ground below the antenna is hard and not exactly what I'd call conductive, even with a ground rod. Not very convenient for laying my planned 50 10-160M radials.

    However, within 50 feet is over an acre of daily watered grass surrounded by a 6 foot chain link fence.

    I was thinking about running 2 shorted RG58 coax runs from & connected to the counterpoise connection at the antenna's base. One to the fence and one to a copper ring or strip just below the grass. To this I would connect the radials fanned out and cut into the grass. Some of the the shorter radials can be at the base and covered with loose dirt, but the dryness would still be an issue.

    OK guys... Am I on the right track? What say you???

    Jeff
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Dryness isn't an issue because soil is a lousy conductor whether it's dry or wet. The radials are what reduce ground loss, not the moisture in the ground (which really doesn't do anything).

    I'd just install the 50 radials you planned on using and lay them on the ground. You can hammer in lawn staples using a small hammer if pushing them in doesn't work, just to hold them tightly against the ground and keep them out of the way.

    The connection from the radials to the feedpoint of the antenna should be short and direct, not 50 feet away. 50 foot runs of "shorted RG58" have a lot of impedance for RF and no matter what's on their far end I doubt they will help.

    BTW, there are desert locations with far better "soil conductivity" than wet marshes in Florida. As far as I can tell, and I've been installing HF verticals for over 40 years, the only kind of "wet" that really helps is salt water. I lived in a very marshy location at the Jersey shore, but about one mile from the ocean, and I could not tell any difference between when the land was absolutely flooded (with fresh water) vs. when it was bone dry during a summer drought. The conductivity comes mostly from mineral content, not moisture.
     
  3. KI6BCX

    KI6BCX Ham Member QRZ Page

    :confused: Well I'm not about to front for a mineral survey, so I'll just take it on faith. :rolleyes:

    However, if for no other reason than to spare my back and FUBAR knees... I'm wondering if I'm over thinking the number of half wave radial lengths???

    My plan was to go with: (I found a 100m tape at Harbor Freight) 5/5m (10m),

    5/6m (12m), 5/7.5m (15m), 5/8.5m (17m), 5/10m (20m), 5/15m (30m),

    5/20m (40m), 5/30m (60m), 5/40m (80m) All using stranded and solid #14 & #12 THHN I got a killer deal on from a retiring electrician.

    BTW... I also scored a 3/4 roll of uninsulated #12 stainless steel shock fence wire. Opinions on SS Vs. copper radials are also welcome.

    So I guess my question is... Should I split (1/4 & 1/2 wavelengths) the difference and perhaps add to the number of multi-purpose radials? Or, will my original plan provide better results?

    Jeff

    P.S.; Please don't anyone be shy about going with the "long answer". Just keep to plain english as much as possible. :D
     
  4. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    Use the chain link fence..
     
  5. K7FE

    K7FE QRZ Lifetime Member #1 Life Member Platinum Subscriber QRZ Page

    1/4 wave radials will be just fine. The electromagnetic field does extend beyond 1/4 wave, however most of the energy is within the first 1/4 wave.

    Are you installing a flag pole antenna or a plain view trap vertical?

    Buried stainless steel will rust and eventually dissolve away. Rust is a poor conductor. Above ground SS fence wire would be fine.

    73,
    Terry
     
  6. KI6BCX

    KI6BCX Ham Member QRZ Page

    I'm going with the ZeroFive 43' Vertical w/Unun 10-160M. And yes, I'm fully aware 160M on this antenna for listening.

    :confused: The books (note that I give preference to age and treachery) say 1/2 wave is the standard for radials, but never really state why.

    So if the energy is within the first 1/4 wave, does going 1/2 wave attract twice the energy and more distant stations? Or is 1/2 just one of those old skool rules of thumb from the days of Marconi?

    Also, when cutting for 10m... Should I stick with 1/2 wave lengths and adding numbers to the multi-purpose radials? Or cut to 1/4 to keep the separation, for as much as there is?

    Jeff
     
  7. N4OGW

    N4OGW Ham Member QRZ Page

    There is no need to cut radials to 1/4 (or 1/2) wave for each band when they are placed on or in the ground. Just make them all 1/4 wave for the lowest frequency. The exact length is not critical.

    Tor
    N4OGW
     
  8. K7FE

    K7FE QRZ Lifetime Member #1 Life Member Platinum Subscriber QRZ Page

    Since you are installing the radials under the soil, their length does not need to be a resonate 1/4 wave. They will interact with the soil and throw the measurements off. You might just install a bunch of radials about 66 feet long. They will no longer be radials, but will be a ground plane (except for 80M) that your vertical is mounted over.
    73,
    Terry
     
  9. N0AZZ

    N0AZZ Ham Member QRZ Page

    I have all of mine cut 1/4 length for 10-160m the easiest way to do radials is to use lawn staples (bought on eBay for ground radials by a ham cheaper). All you need to do is cut the grass very short once and lay out your radials, I place a ring terminal on the end of them and use a nail to hold them order plenty I use then about every 2' or so. Then all you do is push the lawn staples in with your finger or thumb they have a sort a W shape on the top to make them easy to place job goes very quick.

    After you mow the yard a few times unless you mow it very short or scalp it you will never see them in a month after laying them.
     
  10. N5YPJ

    N5YPJ QRZ Moderator QRZ Page

    I don't know where the "wet ground" myth came from but just because the ground is damp or wet doesn't make it a better RF ground though it certainly does at 60 hz AC!

    I'm using a Hustler 6 BTV with 47 20 ft radials on 40 - 10 mtrs and it allows me to make contacts. If I could change one thing I would install the same antenna on my roof top but this is it for now. I can't say it is a great DX antenna or that it defies what other hams say, it doesn't but it allows me to make contacts and some of them are 40 meter DX contacts.

    Be consistent - figure out what are the longest radials that you can install in your personal area and do it. In my case 20 ft is what fits, others may get 35 ft or 65 ft radials. Several short radials are said to work better than a few long radials.

    If you have any soil at all and it bends your radial staples try using a soaker hose for an hour or two to soften the ground.
     
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