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

Hey, like I said, magic. Bent coat hangers also radiate. The fuselage
gives you a place to terminate the coax shield. Wiggle the connection to
the radiator until the SWR is not too bad.

Also, don't get hung up on "conductivity." Both soil and water have less
than silver, but the resistance is what counts and that's the product of
conductivity and conductor cross-section. If it floats your boat, it has a
LARGE cross-section.

Roger (changing radar detector diodes in 1955)

http://home.earthlink.net/~derbyrm

"Brian Whatcott" wrote in message
...
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

So you're saying that IF the resistance of the sea return path is less
than the resistance of copper, the sea will provide a better return
path. Not much value there. IS the resistance of the sea return path
greater than the resistance of copper? How do you know that? Because
boats float?

You should be aware that at HF, the skin depth is a mere fraction of a
foot so the "conductor cross-section" is fairly small. You might want to
consult an expert.

The readers of this newsgroup are probably aware that, ceteris paribus,
lower resistance grounds are better than higher resistance grounds. What
is at issue here is whether 400 sq. ft. of copper is unusable (no better
than nothing at all) as an RF ground on a vessel, and whether only a
return patch capacitively-coupled to the sea can work.

By the way, your formula for capacitive reactance is in error through
the omission of a variable for Capacitance.


Roger Derby wrote:
Hey, like I said, magic. Bent coat hangers also radiate. The fuselage
gives you a place to terminate the coax shield. Wiggle the connection to
the radiator until the SWR is not too bad.

Also, don't get hung up on "conductivity." Both soil and water have less
than silver, but the resistance is what counts and that's the product of
conductivity and conductor cross-section. If it floats your boat, it has a
LARGE cross-section.

Roger (changing radar detector diodes in 1955)

http://home.earthlink.net/~derbyrm

"Brian Whatcott" wrote in message
...

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

Sorry, Chuck. If you don't understand what I'm saying, then I've either
expressed myself badly or you haven't read it accurately. I do have both
the academic and practical background and experience to express an opinion
and despite your prejudice, it is not automatically wrong.

Roger

http://home.earthlink.net/~derbyrm

"chuck" wrote in message
link.net...
So you're saying that IF the resistance of the sea return path is less
than the resistance of copper, the sea will provide a better return path.
Not much value there. IS the resistance of the sea return path greater
than the resistance of copper? How do you know that? Because boats float?

You should be aware that at HF, the skin depth is a mere fraction of a
foot so the "conductor cross-section" is fairly small. You might want to
consult an expert.

The readers of this newsgroup are probably aware that, ceteris paribus,
lower resistance grounds are better than higher resistance grounds. What
is at issue here is whether 400 sq. ft. of copper is unusable (no better
than nothing at all) as an RF ground on a vessel, and whether only a
return patch capacitively-coupled to the sea can work.

By the way, your formula for capacitive reactance is in error through the
omission of a variable for Capacitance.


Roger Derby wrote:
Hey, like I said, magic. Bent coat hangers also radiate. The fuselage
gives you a place to terminate the coax shield. Wiggle the connection to
the radiator until the SWR is not too bad.

Also, don't get hung up on "conductivity." Both soil and water have less
than silver, but the resistance is what counts and that's the product of
conductivity and conductor cross-section. If it floats your boat, it has
a LARGE cross-section.

Roger (changing radar detector diodes in 1955)

http://home.earthlink.net/~derbyrm

"Brian Whatcott" wrote in message
...

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