On Mon, 30 Apr 2007 03:53:06 GMT, Owen Duffy wrote:


I have been playing with some NEC-2 models of a multiband vertical with
radials.

The vertical is an unloaded vertical of 13m height, and it is mounted on
a 6m high grounded metal mast, and an ATU installed at the feedpoint
(base of the radiator). I have fitted a pair of opposed nominal quarter
wave radials for each of the 80, 40, 30 and 20m bands.

[snip]
Comments, thoughts?


Owen.

My first thoughts are while such a situation can be modeled, in the
real world I would doubt you can build a system as you describe where
the radials are balance. Just as one can not install a dipole in a
typical back yard (garden) that is truly balanced.

My two cents worth. G

Danny, K6MHE

Danny Richardson wrote in
:

....
My first thoughts are while such a situation can be modeled, in the
real world I would doubt you can build a system as you describe where
the radials are balance. Just as one can not install a dipole in a
typical back yard (garden) that is truly balanced.

I agree that practical antennas on suburban blocks are a challenge. But
that doesn't eliminate the effects, and I think the key issue that the
models raise is the value in effectively decoupling the mast / feed line.
Tuned radials are not the only method, and as I suggested in my post, short
of measuring the mast current, I cannot see any other obvious method of
"tuning" the radials for maximum decoupling.


Owen