Buried BARE radials of sufficient number will show far less "tuned" behavior and self-terminate more rapidly.
BURIED bare wire radials and ON THE GROUND bare radials measure quite differently. This too is something you can verify by experimenting with a bare wire DOG on top of the ground vs an entirely buried bare wire DOG. It is important to keep all the permutations cataloged and separate in the discussion. Many people are adopting a construction technique as primary over performance considerations, e.g. lay out wire and hold them down with lawn staples and let the grass grow up around them, holding them in suspension OVER the dirt, rather than notching them DOWN INTO the dirt. Grass supported bare wire radials will exhibit tuned characteristics and a higher velocity factor than buried bare radials. As this is almost exclusively done for a single band antenna, it is completely satisfactory for its intentions. It's the MULTI-BANDING that throws a monkey wrench into the works. My original posting is specifies BURIED BARE WIRE radials, placed by notching them into the dirt below the grass, (no laying them on top of the grass). These buried bare radials will be essentially self terminating at frequencies where they electrically exceed a quarter wavelength. and will exhibit a much lower velocity factor than those supported in the grass weave. On frequencies where the buried bare radials electrically are shorter than a quarter wavelength (lower bands), depending on the dirt, even buried bare radials can show some of the tuned behavior of on-top or insulated radials because the radials have not reached a self terminating length. Insulated radials will always show significant tuned behavior. With the 151' insulated wire DOG, I can always find resonance, whether buried or lightly strewn across the leaves touching nary even a single blade of grass. The controversy that I am aware of concerns purported RF current in the ground itself and concentric zones of conduction set up by interaction between the vertical element and the radial-induced spreading ground current, similar to Fresnel zones. 73, Guy. On Mon, Dec 20, 2010 at 6:44 PM, Steve Ellington <[email protected]> wrote: > Guy: > Very interesting.... > > Some of your comments were verified in a recent QST article. > > Mar 2010 - QST (Pg. 30) > > An Experimental Look at Ground Systems for HF Verticals > The author experimented with resonant vs nonresonant radials on the ground > and found performance improved when the radials were cut to electrical > resonance vs just measuring them with a tape. > > Given this, it stands to reason that if the same radial field is used by a > multiband vertical on a higher frequency, the high current point would be at > some distance from the antenna's base thus reducing efficiency. > > Now here's the question.... > Folks assume ground radials to be (non resonant) but that isn't the case. So > what would be the best solution for a multiband antenna with ground radials? > Well if we follow this idea, we would need multiple 1/4 wavelength radials > for each HF band for best performance. > > My inverted L is 50' up and 150' out. I use a separate elevated counterpoise > for each band. I've found that a ground rod and some buried radials have > virtually no effect. I just use them for lightning protection. > > Steve > N4LQ > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
