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Author Topic: Radial position and directional run  (Read 1411 times)

Posts: 1279

« on: June 27, 2012, 03:48:31 PM »

Hello, I finally got my S9 antenna and S9 radial plate. I have a radial question which I have not found in this forum. I have 500 feet of # 14 insulated solid copper wire I am going to use for my radials. With the radial field in my location this will mean about 18 to 20 radials most the required 26' 9" long. The rest in varying lengths of 4' to 20'. Now for the question. My property slopes down from the antenna location in varying degrees of 20 to 5. I know that the radials need to be straight with no bends running away from the mount, How will the slope of the wires affect the antenna operation (if at all)? I know if this were a ground plane antenna the slope would affect the impedance, but will buried radials have any effect on the impedance? I will be using a 4 to 1 UNUN on this antenna for a hopefull 40 thru 6 meter operation with a tuner capable of tuning a 10 to 1 VSWR.

Thank you for any information on this.



Posts: 376

« Reply #1 on: June 27, 2012, 04:51:09 PM »

AFAIK, as long as you keep the radials straight, a bit of a slope will not increase total loss, but will change the impediance as you say. The radials' job is to help the field lines back to the feed point, so any vertical angle should work as long as it's pointing straight back to the feed. Since your antenna will be sort of a half-reversed half-regular ground plane, I imagine it would affect the radiation pattern compared to the same vertical on a perfectly flat radial field.
Buried radials mean more loss, the deeper the lossier, so if you bury your radials so deep that none of the energy gets through to them (useless radials) you'll have an almost perfectly "matched" antenna in terms of VSWR.

I'll now wait to hear from somebody who knows their antenna theory better than me and has the EZNEC plots and practical experience to show for it. I'll just say that I've run verticals on ground sloping just as much as you have, without any particular issues matching the impedance. Smiley
« Last Edit: June 27, 2012, 04:57:02 PM by LA9XSA » Logged
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