mark_n2mh wrote: > Thanks to LW, SD, and Eric for answering my request. > > Sorry for any confusion, but the antenna as given to me, has no > radials at the present time. I will have to fabricate them. > > My original thought was to make the antenna work in its original > frequency range, 30-40 MHz. This would eliminate one variable of > having to make it work outside of its intended range. With the catalog > information from Eric, I've changed my mind and will now proceed > directly to 10 meters as suggested by LW. > > I'm interested in using the antenna in the 10m beacon band, > approximately 28.250 MHz. So, as LW suggested, I will cut four radials > for 1/4 wL, which I calculate to be 105 inches. And, Eric's catalog > shows the vertical piece to be 1/2 wL which I calculate to be 209 > inches. This will be my starting point. Of course, changing the length > of the vertical element is easier than changing the length of the > radials, so that is how I will tune the antenna to resonance as > suggested by SD.
Ground plane radials are typically a few % longer then a quarter wave. So for 28.25, 234/28.25=99.4". Add 5%= abt 104.4". So 105" is good. Also I remember there is an optimum angle to "droop" them to get the main lobe at the horizon-I want to say between 30 and 45 degrees down from horizontal. Affects impedance too if I remember...it's late....
