Topband: Fwd: radals fer 160m vertcal

[Joe Subich, W4TV]

On 5/4/2012 10:01 PM, Merv Schweigert wrote:
> I find a big difference in 160 compared to a 4 radial GP type system
> on 40 meters, maybe if the radials were much higher and less coupling
> to the ground they would work better.

Purely on a logical basis there are two factors working against the
(sparse) elevated radials on 160 meters vs. 40 meters.  First the
160 meter radial system is 1/4 as high in terms of wavelength than
the 40 meter system  ... that means fields in the (lossy) dielectric
are 16 times greater.  Secondly, the skin depth is much greater on
160 than on 40 meters meaning there is greater volume of dielectric
to generate losses.

I don't have the tools to really calculate the difference but I would
postulate that the dielectric (ground) losses increase at some rather
high exponential (perhaps as the square squared) rate as frequency
decreases.  When this is coupled with "short" radial systems - even
those that are "dense" close to the antenna or dense in only one sector,
the losses can really get out of hand.

73,

    ... Joe, W4TV