Topband: Elevated radial number vs efficiency

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Yes, the antenna modelling is helpful, but by no means definitive.

Several years ago I put up a top loaded vertical over a very limited buried 
radial field, 16 x 20 m. It worked, but nothing exciting. It was very hard 
work burying wire in very hard ground.

I then put up an elevated radial system, starting with a pair, tuning them 
like a dipole. Same with the second pair. After four, the tuning didn't seem 
at all sensitive. I ended up with 7 x 1/4 wave radials, plus a shorter one 
where the property boundary was too close.  The radials were about 2.5 m 
high, just high enough to not touch with my outstretched hand. That seemed 
to work quite ok, compared with a full wavelength doublet antenna up 20 m.

I then moved and set up the top loaded now trapped vertical over elevated 4 
x 1/4 wave radials for 160 and 4 x 1/4 radials for 80 m. I quickly tired of 
repairing fallen radials where a horse had rubbed on a post or where I 
caught the wire on the tractor exhaust pipe! Again, it worked me a decent 
amount of DX. And I mean "DX" as nearly everything is a very long way from 
VK3.

Last year, I did the work of burying 60 x 33 m radials, clearing away the 
mess of overhead wires. Does that work any better than the elevated radials? 
I cannot know, as there was no means of comparative testing. But, it's a 
whole lot tidier with the wires under the ground than overhead.

My conclusion is that elevated radials do work quite decently, and they are 
probably a little less work than burying a decent radial field. Wires on the 
ground were never an option, with livestock in the paddock. My suggestion, 
and the references too, is to put the elevated radials up as high as 
practicable (higher than I had them). This allows easy access to vehicles to 
drive under them, without tearing something down.

The aim of the radials is to reduce the effect of ground return path losses, 
and even with 8 radials, I could drive under them, listening to Radio 
National on 621 kHz, and the signal would be significantly attenuated. All 
of the above observations were over fairly poor ground, decomposed granite, 
with granite rocks floating. There is water underlying, however.

73, Luke VK3HJ