Topband: Deep earth rod vs radials

[Brendan Minish]

On Mon, 2009-03-16 at 07:59 -0700, Jim Brown wrote:
> On Sun, 15 Mar 2009 17:28:27 -0700, Robin wrote:
> 
> >Do you know of any DATA about radials or meaningful ground return systems 
> >using salt water ABOVE the metallic conductor?

Salt water is an excellent conductor compared with the earth and works
very well under HF antennas, it is however a poor conductor compared to
copper.

Like all conductors Salt-water exhibits the skin effect where RF is
concerned, therefore contact area with the surface of the sea is much
more important than simply achieving the best low DC resistance contact
with the salt water.

A wire 'chucked' in the sea and used as an RF ground may not perform
very well because only the section near the surface of the water will be
effective for connecting RF to the sea within the area where the skin
effect dominates over the resistive losses between the wire and the
surface.

Radial(s) above the water or on the surface are far more effective than
radials under the surface. An ideal salt-water RF ground is a large
steel or aluminium boat and as an added bonus this RF ground will serve
as a good place to enjoy a few beers on a pleasant summer's evening.  

RF grounding on fibreglass and timber boats can be problematic, it's
generally done by bonding the tanks engine etc together, combined often
with areas of copper foil or mesh inside the hull, however this is much
more effective where the areas of bonded metal are near or above the
waterline. I have seen quite a few terrible HF radio installations on
sail-boats and only a few good good installations. 

73
Brendan EI6IZ 


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