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Elevated radials, counterpoise?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W6OGC, Apr 25, 2014.

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  1. W6OGC

    W6OGC Ham Member QRZ Page

    I had more or less thrown in the towel after being frustrated trying to put radials down for some sort of vertical here on the Rock Ranch. There is not enough top soil to stick lawn staples down to hold the radials. I am also height limited due to HOA regs, to something less than about 39'.

    I keep thinking about the SteppIR BigIR in my garage, which is 32' high. Ground mounting it presents the radial problem. Mounting it as a ground plane could run into the max height issue.

    I've been reading "Low Band DXing" particularly the sections about elevated radials. This suggests I could put the vertical close to the ground and run the radials upwards, maybe 5-10' at the ends. Could this possibly work? I could fence off the area to keep wanderers out, and this would be in a well-fenced large back yard anyway.

    Speaking of fences, this fence is very stout, about 5' high, a wire mesh that goes >100' back to the property line then along the rear llne probably another 300'. Would there be any point in tieing the radials, or counterpoise, to this fence somehow? Anyone ever tried this? A power line to the neighbors is right above the rear fence section.
     
  2. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    I don't think that's a particularly good idea because it probably cancels out radiation occurring from the radiator element in the Fresnel zone.

    I am also thinking folding the elevated radials upward toward the radiator, may also significantly change the intended resonance point of any tuned traps or coils installed on the antenna design.
     
  3. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I'd give it a try, myself.

    I had a large HF vertical installed on my very sloped hillside property in Chatsworth for a few years. Radials ran from the feedpoint downhill towards the house, uphill towards the back fence, sideways towards the two side fences, just all over the place. A few were "level," most weren't, and at least a dozen radials ran uphill so the ends of the radials were 10-15' higher than the feedpoint.

    Seemed to work fine.:p

    I don't think 5' at the ends of radials is really "elevated." There will still be a powerful ground influence, and using resonant radials may not even have any meaning. Based on decades of playing with HF verticals, my impression is that "elevated" verticals means they're about 1/8th wavelength above ground at the base: On 40 meters, that would be about 17 feet. On 80m, more. Even on 20m, more then eight feet.
     
  4. W1FBV

    W1FBV Ham Member QRZ Page

    I would guess (only a guess) that radials should not run much higher than the base of the antenna. I have read somewhere that elevated radials will work OK even if a foot off the ground, and in fact I have used a temporary vertical with radials only a foot off the ground. It seemed to worked fairly well. Goggle or the ARRL archive might give you more information on this topic.
    73, Jim W1FBv
     
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    On HF, "not much higher" could easily be five feet, which is a really short portion of a wavelength on HF. It's only a quarter-wave on six meters.

    I'd try it.
     
  6. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Gong back to the AM broadcast band experiments with 4-elevated radials 6-feet off the ground on 600 kHz, 1000 kHz, and 1500 kHz, it was found that the antenna radiation was basically equivalent to 120-buried radials. The 6-feet at 600 kHz equates to 2-feet at 1800 kHz, 1-foot at 3600 kHz, and 6-inches at 7200 kHz!

    Also, remember, in "average" soil, the r.f. ground is usually between 6-feet and 8-feet below the surface. Of course, in some parts of Alaska, r.f. ground is many feet below the surface. That does help the radials.

    Before my swimming pool was installed, I had 60-buried radials under my ground mounted HyTower (well, about 6-inches off the ground). Then, when the hole was dug for the swimming pool, a lot of the radial field was "dug up". So, I installed 4-elevated radials for 80-meters, 4-elevated radials for 40-meters, and 4-random length radials that start at the bottom of the HyTower and then go along my wood stockade fence, along the retaining wall for the swimming pool, along the slab foundation for my house, etc. Those radials are at various heights above the surface starting about 4-feet from the HyTower and are at about 2-feet, 4-feet, and 6-feet above the surface. Also, because of the size of my yard, most of the radials do not go in a straight line but, make at least one 90-degree turn and, in the case of the 80-meter radials, make 2-each 90-degree turns.

    I also have a 40-meter vertical, that I can phase with the HyTower for gain on 40-meters, that also has elevated radials that go in a similar pattern as those for the HyTower.

    My experience has been that the elevated radials definitely work better than the 60-buried radials.

    Glen, K9STH
     
  7. K7MEM

    K7MEM Ham Member QRZ Page

    W6OGC,

    I live in an area that's probably just as rocky as your area. We are considered the Flagstone Capitol of the United States and are surrounded by six old volcanoes. You can't dig without a jack hammer. Added to that I have several thousand feet of horse fencing made from 2" iron pipe frame with 4 strands of 3/8" steel cable. And that's just the front area. The back area is 5 strands of barbed wire. With my shack in the barn, there is no place for ground radials.

    My solution was to raise the antenna and use downward sloping radials. The antenna (5BTV) is mounted on a 18' section of 2" iron pipe that is secured to a corner of the cattle pen. I use four tuned radials for each band (80,40,20,15, and 10M). The ends of the radials are about 10' above ground, which allows me to get my tractor underneath. Overall, the antenna works great. It's a little tedious getting it initially tuned because of it height.

    I have tied using the fence as a ground, but it didn't work very well. Most of the fence posts are isolated in cement and the horses have a habit of knocking the welds loose. I have had them bend a stall gate and kick out the 1" thick solid iron bars.

    I have been thinking of mounting the 5BTV on top of the barn. The barn is 50' x 50' and has a metal roof.
     
  8. W6OGC

    W6OGC Ham Member QRZ Page

    Chapter 9, "Low Band DXing" Fourth Ed. ON4UN

    This is part of what I have been noodling over to make sure I understand it well enough to implement something for the BigIR that still meets the limitations.
     
  9. WA7DU

    WA7DU Ham Member QRZ Page


    Erect your vertical radiator, lay down the radials (lots of them) on the ground, cover them with a good-quality weed cloth, cover the weed cloth with coarse sand, pea gravel, lava rock, river rock, or any other similar "weighty" mulch. (And, of course, at some point, run your feed line.)

    Confession: I've never done this, so I cannot say with absolute certainty that it works--let's see if it gets feedback from the experts who spoke earlier, and any "new" ones who choose to respond--they will be "vocal" if its a dud idea.
     
    Last edited: Apr 26, 2014
  10. KM1H

    KM1H Ham Member QRZ Page

    Low Band Dxing and modelling show that radials can slope up at a maximum of a 45 degree angle for 10-20' and help establish the radial curtain over the ground. I did that with my 160M radials from 10 to 20' and then thru the woods; worked very well over a granite hilltop with solid rock only 1-2' down.

    Tying radials to a fence is fine as long as they make good electrical contact AND the fence is electrically conductive thruout otherwise RF could cause RFI.

    Carl
     
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