In article ,
"Charlie J" wrote:

Gary was proposing a significant departure from "conventional wisdom" in
recommending the placement of the antenna coupler/tuner closer to the
counterpoise/rf ground than is conventionally done. I asked if there was
any objective evidence that showed that placing the antenna coupler/tuner
immediately adjacent to the counterpoise half of the antenna system truly
offered measurable improvement, on a non-metal pleasure boat... today.

Charlie,
Counterpoise is a non-issue in MF/HF Marine Radio systems as most of
the "non-metal pleasure boat" vessels aren't large enough to have such
a thing installed. To be effective the "Counterpoise" would have to be
1/4 Wavelength at the lowest operating frequency. Say 2182.0 Khz.
That would be around 90 ft or so and that's much longer than the hulls
we are talking about. Also consider that if one could build a
counterpoise Rf Ground system onboard a plastic hulled vessel, the
couterpoise would be raditaing half the applied power from the
Transmitter into everything that was capacativly coupled to the devised
counterpoise. Then in a mutiple Frequency installation that most Marine
Radio systems are, to be effective, a couterpoise Rf ground system would
need a tuned element for each band segment of the system. the autotuner
takes care of the antenna side but what tunes the couterpoise for each
different frequency? It does need to be tuned to be an effective
"counterpoise" So forget counterpoise. Now, concider "Coupling to the
Seawater" for effective RF Ground. the Seawater is an effenctive low
impedance Rf Ground that is nonreactive across the MF/HF Specturm.
It doesn't need to be tuned. Get out your (if you have one) RF Network
Impedance Bridge, and sweep the MF/HF Spectrum of a well coupled
Seawater RF Ground System, on a Plastic (non-matalic hulled) Vessel.
Then come back and tell us about what you have found. We would be
interested in what your "conventinal wisdom" would be after undertaking
some rather basic experimentation.

Yes, having the autotuner as close to the RF Ground System is one
of the Basic Critical Rules, that your "conventional wisdom" doesn't
even consider, to is detriment. Simplistic "conventional wisdom"
just leeds to "the blind leading the blind" metality, and perpetuates
Junk Knowledge. I see you are a ham, so you must have some rudimentary
knowledge of RF Physics. RF Network Analysers were invented to allow
folks to quanitfy the complex impedance of RF systems, so that even
non-RF Engineering types could figure this stuff out, emperically,
rather than on a Mathamatical Formula, that could only guestimate what
was actually happening.

In Marine Radio Systems on Plastic Hulled Vessels, antenna system
compromises are preety much the order of the day as space and length
just aren't available for anything that comes close to Ideal criteria.

Your experiences may be different than mine, but the Basic Laws of
Physic's don't and haven't changed since Marconi, and after all he did
Invent the Marconi Antenna System that we are all trying to duplicate on
the vessels.

Bruce in alaska
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