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-boun...@mailman.qth.net [mailto:elecraft-boun...@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@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
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