[Elecraft] OT: Elevated vs. Buried Radials

[Joe Subich, W4TV]

The SteppIR information is overly simplified.  For the best current
analysis of elevated vs. on ground radials see the extensive data
from N6LF - http://www.antennasbyn6lf.com

In particular, read the comments on elevated radials:
http://www.antennasbyn6lf.com/2011/02/comments-on-elevated-radials.html
studies on ground systems:
<http://www.antennasbyn6lf.com/2009/12/series-of-qex-articles-on-ground-system-experiments.html>
and studies on elevated radial systems:
<http://www.antennasbyn6lf.com/2012/02/elevated-radial-ground-systems-some-cautions.html>

One of the major red flags with elevated radials - they must be a major
fraction of a wavelength (1/8 wave is a good rule of thumb) before they
really act independently of the "dirt".  Even then, nothing will reduce
the losses in the 1 to 10 wavelength area responsible for forming the
low take off angle lobe.

73,

    ... Joe, W4TV


On 5/18/2013 1:36 PM, Ron D'Eau Claire wrote:
> Hi Joel:
>
> This is a very good summary that clearly shows the difference between
> elevated and in-ground radials. (See Figure 1 on the second page)
>
> http://www.steppir.com/wp-content/uploads/2011/10/radial-systems-for-vertica
> l-antennas.pdf
>
> Bottom line, if you can install a LOT of in-ground radials (the A.M.
> broadcast stations use about 100), the efficiency of the antenna will be
> high. If you can install resonant elevated radials, a much small number will
> produce even higher efficiencies.
>
> In ground radials do not need to be very long. About 0.2 wavelengths seems
> to be as good as a much longer radial. Above ground resonant (1/4 wave long)
> radials take up a lot more room.
>
> Some A.M. Broadcast stations in the USA have used elevated radials with
> great results. At least one was described in an A.R.R.L. antenna compendium
> a few years ago. However, their antenna configurations are controlled by the
> F.C.C. so they must go through approvals for the design. And resonant
> elevated radials at those frequencies are rather long!
>
> 73, Ron AC7AC
>
> P.S. The only FOD I know about is "Foreign Object Damage" - the nemeses of
> jet engines. Haven't a clue how that applies here, Hi!
>
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Joel Black
> Sent: Saturday, May 18, 2013 5:37 AM
> To: elecraft
> Subject: [Elecraft] OT: Elevated vs. Buried Radials
>
> A lot of talk has been going on about radials on the KX3 Yahoogroups
> Reflector, but there is so much FOD on that reflector, I usually delete most
> of the messages.  Although it may have been mentioned there, I have probably
> missed it.
>
> Other than for portability, why are elevated radials so important? I have a
> ground-mounted 6BTV (not my main antenna) in my backyard. I have four
> radials for each band and they were all put in with yard staples.
> I did this in the Fall after the last grass cutting.  By Spring, the grass
> had grown over them.  Now, several years later, there is at least one inch
> of dirt over them.  In all honesty, it's only a backup antenna and probably
> needs some radials replaced.
>
> Now, in my situation, there was no way I was going to use elevated radials.
> Someone recently posted a link to the SteppIR vertical - the CrankIR.
> Looking at the one page from the link, it only mentions elevated radials.
> Now, I've never seen a loaded-tower broadcast antenna with elevated radials
> either.
>
> Is the only benefit portability?
>
> Please, I do not want to also be accused of perpetuating FOD on another
> reflector.  I'd prefer you reply directly to me.  If needed, I'll summarize
> and repost.
>
> Thanks,
> Joel - W4JBB
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>