On Sat, 30 Jul 2005 19:35:36 GMT, Me wrote:

In article ,
"Roger Derby" wrote:

When you talk of capacitive coupling, frequency does matter. (Xc =
1/[2*pi*F]) There's two orders of magnitude difference between HF at 1.8
MHz and VHF at 180 MHz.

"Ground" is one of those elusive concepts that get more magic/conundrum (aka
BS) than it deserves. A full dipole needs no ground. The whip or backstay
needs a ground plane so that its "virtual image" creates a full dipole.

Note that aircraft use HF communications with a half dipole antenna
(trailing wire) with no ground plane. Of course they do have an excellent
antenna height. (Don't hold the end in your fingers to test on the surface.
When your boss hits the transmit key, it hurts, for weeks.)

Antennae are magic.

Roger

Actually the aircraft skin, if metal, or in the case of doped fabric
covered planes, the tube frames, becomes the RF Ground system for
aircraft MF/HF antenna systems. Thats why you almost NEVER see an MF/HF
Radio installed in a spruce framed, fabric coverd, aircraft, and if you
did see one it wouldn't work very well.


Me who actually has an Aircraft Endorsement on
his First Graph ticket.....


Ah, well, well!
How much area does a light aircraft tube fuselage etc., subtend?

Could it possibly be, like, 200 sq feet?
And it can transmit successfully, using this as its ground plane?

You mean, like a 200 ft ground plane in a boats cabin overhead?

:-)

Brian Whatcott