Hi Steve et. al.,
On the ground, The minimum recommendation is 30 radials about 20 meters/65
feet long on the ground. There is no exact dimension for radials to avoid
resonance interaction. Elevated radials are OK, but should be reinforced
with radials on the ground. Putting feed point on the ground is the Battle
Creek recommendation. You could put up 6 to 12 elevated radials if you will
be enhancing the ground with radials.
On the top loading wire: If you use a coaxial trap for 80 meters, it makes
the end loading wire in the order of 40 feet or 12 meters total if an
inverted L configuration is used. The references I have say the length of
two wires is about 0.71 times single wire length, so a couple of wires about
30 feet or 9 meters each should do the trick.
ON4UN is trying to cancel horizontal radiation and optimize vertical
radiation with the two top loading wires. That is why he recommends the
double top loading.
Good luck 73 George K8GG
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