Owen wrote:
I have been exploring models of a quarter wave monopole over a set of
radials on 80m using NEC4 models.

If my models are valid, and they use 'average ground', the indication is
that while it may require a large number of buried radials (16) before
efficiency levels off a bit, similar efficiency can be obtained with
just three radials elevated more than 100mm above the soil.

This leaves me wondering why the popularity of extensive fields of
buried radials for the lower bands.

Comments?

Owen

I would think that the buried radials are more convenient (broad band, etc.)

Look at the performance of your ankle biting radials when the dimensions
are changed slightly.. For instance, if you shorten them by 5%, does
it make a big difference? For the buried radials, the length is very,
very non critical.

Something else to look at is the sensitivity of "efficiency" (and your
definition of radiated power in the hemisphere/power into antenna is
fine) to soil properties.. if the soil conductivity or epsilon changes
(as it will with changing water content) does the efficiency change rapidly?

Also, what about the loss in any matching components needed (e.g. if you
had a real efficient narrow band antenna, then operating off nominal
means you'll need a different matching network, and the loss in it might
be worth considering)