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Old June 1st 06, 08:55 PM posted to rec.radio.amateur.antenna
Bruce in Alaska
 
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Default RF grounding methods for sailboats: A Summary

In article ,
Richard Clark wrote:

If they all utilize the same seawater for propagation and the same
vertical radiator, they all suffer equally - it stands to reason there
is no difference given all the "sameness." It also stands to reason
by your assertion that they differ, that they do not all use the same
seawater or vertical.... Which is it? Let's skip that and cut to the
heart of the matter. How MUCH different?

Start with a conventional untuned vertical using a dynaplate and tell
me, in dB, how much better any other scheme is. Let's confine this to
a practical situation where the rig is under cover and inside the boat
and that you need two leads, one from the tuner antenna connection,
and another from the tuner ground connection.

73's
Richard Clark, KB7QHC


This is exactly right. If they all use the same water for RF Ground,
and vertical, for the antenna, then the only difference is, "How much
coupling from the ground stud on the antenna tuner does each system give
to the water?" And that is the Thousdan Dollar question. DynaPlate,
Bonded RF Ground System, wires, radials, whatever, all, just make up one
side of the capacitor, with the water as the otherside and the distance
between is the dielectric. More effective coupling equals lower
impedance RF Ground. All this talk of Modelling is just so much FuFurrR,
for anyone who has installed MF/HF Marine Antenna Systems on these type,
wood or plastic vessels. Anyone with much experience in the field will
tell you, simply, get as much surface area as possible, bonded with
low impedance connections, (Copper Strap) and get it as close to the
water as possible. The Physics of building a bigger capacitor is:
Have as much surface area as possible, with the least space between the
plates. This isn't Rocket Science, it is just basic physics, and all the
crap about tuned counterpoises, and copper screens in the overhead, and
the like is just that...... crap...woun't work, never has, and never
will.
It doesn't take a NEC Modelling Software Package to figure this out, it
just takes some common sense and a bit of OJT Experience....

Bruce in alaska
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