doktorij at bellsouth.net
doktorij at bellsouth.net
Wed Jun 14 15:24:37 EDT 2006
I've used wire as small as 22 AWG for radials. They are still doing a fine job 3 years later. My radials are slightly buried so that the mower doesn't get 'em. I had some 10 AWG I also put in, a mower will eat that just as well.
If you use smaller guage wire, you may wish to leave a little slack at the common point, particularly is the ground freezes in your area. A little wiggle room is worth the extra inch or two.
Check you local electrician or junk yard for end of reel deals. I bought 15,000' 16 or 18 from an automobile supply house online for $35 (shipping was brutal tho')
Date: Wed, 14 Jun 2006 16:47:05 +0000
From: "Rob Atkinson, K5UJ" <k5uj at hotmail.com>
Subject: Re: [TowerTalk] re Radials
To: schiers at netins.net, towertalk at contesting.com, jimlux at earthlink.net
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the davis RF price for #16 looks pretty good by current pricing however I am
a bit leery of the physical robustness of #16.
WOR reportedly tried aluminum at one time and it didn't work out for some
reason. Maybe the Al didn't last.
you might think $68 for 1K' isn't bad but if you are putting down 100 1/4 w.
radials for 160 it starts getting pricey for a ham. do the arithmetic.
re the 20' radials--a base fed linear conductor perpendicular to earth comes
under the effect of earth when close, so that earth becomes the mirror part,
or the missing other half of the radiator. the massiveness of the earth
predominates so that any radials buried or laid on the surface aren't the
"mirror part" so much as they facilitate earth return conductivity by
helping overcome resistance of earth ground. Because of that their length
isn't quite as critical. If you could levitate the radiator up into the air
to sufficiently isolate it from earth's surface, then any metal component
(we'll continue to use radials) intended to be the lower half, or mirror,
must perform all of the counterpoise or groundplane function and because it
is a complete antenna component, its length matters. This is why if you
place your radiator up say, 10 feet on 40 m. the radial lengths have to be
measured and cut appropriately.
Studies (I know of at least one IEEE paper on this) have shown that
unusually short radials on the ground or below grade work almost as well as
1/4 or 1/2 w radials, but in this case, "short" meant 45 degrees or 1/8 w.
I think 20 feet is pushing the short envelope. Also, it is critical that
you employ lots of radials to enjoy the benefit of having them. Five or ten
or twenty is not enough. From what I have read, if you put down ninety
radials around 60 feet long, you will enjoy almost the same field strengh in
mv/meter at one km you would have with the same number of radials 1/4 w.
long on 160 meters. Most hams who find ground mounted verticals to be poor
performers simply do not use enough radials.
rob / k5uj
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