There are two ways that you can improve the performance of elevated radials.
First: they work best if at 1/4 wavelength of higher. This gets rid of
losses with the earth. I am sure if you ran a program on this the losses
would get to a point of diminishing returns at 35' for 80 and 80 or 90 feet
for 160.
Second: N4KG reverse radials have both ground loss and loss in the section
of tower below the feed point. If you can put them as high as K3ANS (71' on
160) then you only need worry about losses in the lower part of the tower.
This can be fixed by using capacity to isolate the lower section from the
part that is fed. Ralph O. Robinson (then WA3YEE) presented a piece at the
1975 ARRL National convention on isolating and exciting a metal tower. The
idea he presents could easily be adapted to isolating the towew below the
N4KG feed point. Mr. Robinson holds several US patents (Notch antenna and
dipole radio sonde) and worked for the Applied Physics Lab at Johns Hopkins
when the piece was presented. It very complicated but one isolation
technique called traps is used in many tri-band beams. Even back in 1958
Gonset sold a beam that used capacitor sections to isolate sections of a
tri-bander. KLM adapted this technique for the KT34/KT34XA.
The alternative is to use the big isolators sold by antenna mart (KC4UZ) or
the commercial ones sold by PiRod or Rohn.
N4KG is right that on 160 and 80 using his technique probably puts out a
competitive signal with all but the phased verts, tall verts, or 80 beams at
over 120'. This technique also takes advantage of our single tower for us
small lot guys who can't swing a 130'+ vert.
73, Dave K4JRB
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