In article et,
"Roger Derby" wrote:

We're not discussing theory, we're discussing implementation. VHF and HF
differ significantly due to near-field considerations as well as physical
dimensions. A ground plane for a VHF whip can live on the same pole. For
HF, you'd need a MUCH bigger boat.

We once asked the lab to do a finite element analysis of a hunk of beef
being roasted. They came back later and said there wasn't enough computer
power in the world to do the job due to the various elements (water, fat,
protein, bone, etc.) By the same token, HF antenna theory is useless
because so many things on the boat are part of the "near field." One can't
ignore the rails, the other antennae, the people walking about, ...

In general, I tend to agree with "me" that the sea is the significant ground
plane if we're talking small boats (under 65').
400 sq.ft. of copper is 20' x 20' or so. The wavelength of 4215 KHz is 75
meters = 277 feet.

The magic comes in when the various elements interact. Even small dish
antenna are tested for their radiation pattern before going into production.
Theory, hah. Google antenna "near field" and you'll get sufficient theory,
mostly applicable to small dishes, to convince you.

As Arthur C. Clarke stated, "Any technology which is sufficiently advanced
(or complex) is indistinguishable from magic."

Roger

Roger has it right on....Not much Moss growing under hs feet.....


Me

On Sat, 30 Jul 2005 19:41:03 GMT, Me wrote:

In article et,
"Roger Derby" wrote:


In general, I tend to agree with "me" that the sea is the significant ground
plane if we're talking small boats (under 65').
400 sq.ft. of copper is 20' x 20' or so. The wavelength of 4215 KHz is 75
meters = 277 feet.

Roger

Roger has it right on....Not much Moss growing under hs feet.....

Me

I just had a wild guess that if Roger was agreeing with anonymous
poster 'me' and me was agreeing with Roger, then Roger was probably
going to be in error too.

So I checked a Roger fact: that 4215 kHz = 75 meters = 277 ft.

Here's the scoop:
4215 kHz = 71.2 meters = 233.5 ft

Waddaya know!

:-)

Brian Whatcott