"Meindert Sprang" wrote
"Jack Painter" wrote in message
news3lvc.5786$Y21.4832@lakeread02...
C'mon ol' salt, you should know the inside of copper pipe is
electrically
identical to both sides of copper strap when a bonding connection is
made
to
either. Skin effect of electrical current is felt equally on both in
_that_
condition.

No it isn't. Consider a massive rod of 1". RF flows at the outside due to
skin effect. No remove the innards of the rod, leaving, say 1/16" of wall.
Why would current suddenly flow at the inner surface? It isn't, for the
same
reason it was on the outside when the rod was massive.

Besides, heavy coils in radio stations are all tubes and cooled by running
water through them. Due to the skinn effect, the water is not 'touched' by
the RF.

Electromagnetic induction on a material from one outside
direction sees skin effect on the outside surface only of a closed
structure, cabinet, pipe, etc. But we are not talking about EMF's.

Yes we are. And EMF is exactly the reason why the electrons start to
repell
eachother. And the only place where they are as far apart as possible is
on
the outside of the tube.

Meindert, water is not a good conductor, with average tap water having
100,000 ohms resistance across 1 meter of 15mm plastic pipe filled with
water. Even at RF frequencies, where skin effect is most pronounced, a
bonded connection made equally to both inside and outside of a copper pipe
should exhibit skin effect throughout most of the entire cross section of
the copper pipe. This is because the wall thickness of the copper pipe is
not materially different from copper strap.

Example:

For copper tubing used as a inductor in antenna tuners:

coil length
R= ---------------------------------------
conductivity *skindepth*2pi*coil radius

Now, applying voltage to the outer surface only of copper tubing with closed
ends, whether by EMF attachment or bonded connection to the outside only,
would exhibit surface-only skin effect similar to if a faraday cage was
constructed of the same copper strap we are talking about. The outside
surface would carry most current. But if the voltage connection was bonded
to both inside and outside of an opening of the faraday box or the copper
tubing, then current via skin effect would be nearly constant on the inside
and outside surfaces of the box, defeating the faraday effect. The
condition I originally described, that of a bonded connection, applies
voltage equally and carries current equally on the entire skin of the
conductor, inside and out, 360 degrees, as efficiently as a piece of copper
strap of similar cross section.

Best regards,

Jack Painter
Virginia Beach, Va

In article Wmnvc.6104$Y21.5577@lakeread02,
"Jack Painter" wrote:

Meindert, water is not a good conductor, with average tap water having
100,000 ohms resistance across 1 meter of 15mm plastic pipe filled with
water. Even at RF frequencies, where skin effect is most pronounced, a
bonded connection made equally to both inside and outside of a copper pipe
should exhibit skin effect throughout most of the entire cross section of
the copper pipe. This is because the wall thickness of the copper pipe is
not materially different from copper strap.

Example:

For copper tubing used as a inductor in antenna tuners:

coil length
R= ---------------------------------------
conductivity *skindepth*2pi*coil radius

Now, applying voltage to the outer surface only of copper tubing with closed
ends, whether by EMF attachment or bonded connection to the outside only,
would exhibit surface-only skin effect similar to if a faraday cage was
constructed of the same copper strap we are talking about. The outside
surface would carry most current. But if the voltage connection was bonded
to both inside and outside of an opening of the faraday box or the copper
tubing, then current via skin effect would be nearly constant on the inside
and outside surfaces of the box, defeating the faraday effect. The
condition I originally described, that of a bonded connection, applies
voltage equally and carries current equally on the entire skin of the
conductor, inside and out, 360 degrees, as efficiently as a piece of copper
strap of similar cross section.

Best regards,

Jack Painter
Virginia Beach, Va

Jeeezzz Louise Jack, where did you learn all this BS that your spreading.

But if the voltage connection was bonded
to both inside and outside of an opening of the faraday box or the copper
tubing, then current via skin effect would be nearly constant on the inside
and outside surfaces of the box, defeating the faraday effect.

Please explain how one "BONDS" a connection to only the inside of a
copper pipe. All of the Physic Professors of the World would really
like to know. Are you saying that if one made a "RF Connection",
to only the inside of a copper tube, that no RF would flow on the
outside of the tube? That is just plain wrong, and a stupid statement
on it's face.

ok, enough of this BS, CFR!!! (Call for Reference) Let's see if old
Jack can actually come up with some documentation that RF flows on the
inside of a connected copper tube or pipe. Lets go for some Peer
Reviewed Documentation here, the straight, No ****, Textbook, kind
of documentation, written by some really Qualified Physics Phd's.

Hmmmm, all the PhdEE's that I asked, just laughed and ask how the
weather and fishing was.........

Bruce in alaska
--
add a 2 before @

"Bruce in Alaska" wrote
"Jack Painter" wrote:

Meindert, water is not a good conductor, with average tap water having
100,000 ohms resistance across 1 meter of 15mm plastic pipe filled with
water. Even at RF frequencies, where skin effect is most pronounced, a
bonded connection made equally to both inside and outside of a copper
pipe
should exhibit skin effect throughout most of the entire cross section
of
the copper pipe. This is because the wall thickness of the copper pipe
is
not materially different from copper strap.

Example:

For copper tubing used as a inductor in antenna tuners:

coil length
R= ---------------------------------------
conductivity *skindepth*2pi*coil radius

Now, applying voltage to the outer surface only of copper tubing with
closed
ends, whether by EMF attachment or bonded connection to the outside
only,
would exhibit surface-only skin effect similar to if a faraday cage was
constructed of the same copper strap we are talking about. The outside
surface would carry most current. But if the voltage connection was
bonded
to both inside and outside of an opening of the faraday box or the
copper
tubing, then current via skin effect would be nearly constant on the
inside
and outside surfaces of the box, defeating the faraday effect. The
condition I originally described, that of a bonded connection, applies
voltage equally and carries current equally on the entire skin of the
conductor, inside and out, 360 degrees, as efficiently as a piece of
copper
strap of similar cross section.

Best regards,

Jack Painter
Virginia Beach, Va

Jeeezzz Louise Jack, where did you learn all this BS that your spreading.

But if the voltage connection was bonded
to both inside and outside of an opening of the faraday box or the
copper
tubing, then current via skin effect would be nearly constant on the
inside
and outside surfaces of the box, defeating the faraday effect.

Please explain how one "BONDS" a connection to only the inside of a
copper pipe. All of the Physic Professors of the World would really
like to know. Are you saying that if one made a "RF Connection",
to only the inside of a copper tube, that no RF would flow on the
outside of the tube? That is just plain wrong, and a stupid statement
on it's face.

ok, enough of this BS, CFR!!! (Call for Reference) Let's see if old
Jack can actually come up with some documentation that RF flows on the
inside of a connected copper tube or pipe. Lets go for some Peer
Reviewed Documentation here, the straight, No ****, Textbook, kind
of documentation, written by some really Qualified Physics Phd's.

Hmmmm, all the PhdEE's that I asked, just laughed and ask how the
weather and fishing was.........

Bruce, you're making a totally off the wall argument now, with opposite
assumptions that were never asserted or offered by any of the posters to
this thread. Taking your questions literally as you phrased them would
generate a laugh by all, indeed. If a laugh was your intention, we'll all
have a good one. But I doubt that you are confused about skin effect, or why
a faraday cage works, and specifically what would defeat it's protection
(ie: an opening). So if you seriously think that for instance, a c-clamp
applied across an open end of thin walled copper tubing, contacting the
inner and outer wall in it's grip, would apply voltage differently to the
inside versus the outside of this tubing, then it will be easy to explain
your error in thinking. And since I did not make a joke of your obvious
geometry and math errors in determining the surface area of an object, one
which you continue to be confused about, I would suggest that we either: end
the thread if you do not desire pleasant and professional discussion, or,
omitting the snide comments that do not reflect well on the group or it's
interested participants.

Respectfully,

Jack Painter
Virginia Beach, Va

"Meindert Sprang" wrote in
:


Imagine what 2 meters of coax with a capacity of 200pF ( a "load" of
about 200 ohms at 4 MHz) does to a high impedance (several kOhms at
4MHz) antenna connection: right... almost short circuit it to ground.
NEVER use coax between the ATU and the antenna.


That's just about as bad as neatly tywrapping the wire from the tuner to
the bottom insulator on the backstay to the grounded backstay part UNDER
the bottom insulator. Trying to get them to let that wire HANG away from
everything to lower the capacitance to ground is like trying to get 5200
adhesive that's hardened out of a crack in the decking. They don't care
what it does to the signal output, as long as it looks "neat and tidy".

Larry W4CSC

"Meindert Sprang" wrote in
:


Indeed, it will radiate as much as the antenna does. Therefore it is
best to place the ATU immediately at the feed point of the backstay.
The best practical place would be directly below deck, underneath the
backstay. Every effort to keep the GTO15 as short as possible is best.

Meindert

Where'd this "high voltage neon wire" nonsense come from? The tiny wire
inside there is way too small for when the 50' backstay nears 1/4
wavelength at 5 Mhz where its impedance will be REALLY LOW and its antenna
current at 150 watts will be REALLY HIGH.....SAY 15 OHMS and THREE amps!
There are many frequencies at which the impedance of any sailboat backstay
antenna is LOW, not high! around 5-6 Mhz, around 15-16 Mhz where it
becomes 3/4 wavelength resonant.

I don't like this thin high voltage wire idea. Lionheart has a 8" piece of
#10 copperweld antenna wire connecting her AT-150 tuner to the base of the
backstay. This makes 40 meters just work fantastic with a good ground on 7
Mhz where the antenna's complex impedance is still very low.

73, Larry W4CSC

Sigs 5/8 to 9 in Moldova, Moscow, Czech Republic, Brazil on 7 and 14 Mhz
ham bands. Great fun working DX from Florida from the backstay.

The central conductor of GTO15 isn;t all that thin. Seems to work
well and also seems to be the standard fopr the purpose. I'm
not sure what neon wire looks like.

Doug, k3qt
s/v Callista

"Larry W4CSC" wrote in message
...
"Meindert Sprang" wrote in
:


Indeed, it will radiate as much as the antenna does. Therefore it is
best to place the ATU immediately at the feed point of the backstay.
The best practical place would be directly below deck, underneath the
backstay. Every effort to keep the GTO15 as short as possible is best.

Meindert

Where'd this "high voltage neon wire" nonsense come from? The tiny wire
inside there is way too small for when the 50' backstay nears 1/4
wavelength at 5 Mhz where its impedance will be REALLY LOW and its antenna
current at 150 watts will be REALLY HIGH.....SAY 15 OHMS and THREE amps!
There are many frequencies at which the impedance of any sailboat backstay
antenna is LOW, not high! around 5-6 Mhz, around 15-16 Mhz where it
becomes 3/4 wavelength resonant.

I don't like this thin high voltage wire idea. Lionheart has a 8" piece
of
#10 copperweld antenna wire connecting her AT-150 tuner to the base of the
backstay. This makes 40 meters just work fantastic with a good ground on
7
Mhz where the antenna's complex impedance is still very low.

73, Larry W4CSC

Sigs 5/8 to 9 in Moldova, Moscow, Czech Republic, Brazil on 7 and 14 Mhz
ham bands. Great fun working DX from Florida from the backstay.

Normally, when tywrapping the feedline to the backstay below
the insulator, the lower part of the backstay is not grounded. Otherwise
small standoff are used.

Doug. k3qt
s/v Callista

"Larry W4CSC" wrote in message
...
"Meindert Sprang" wrote in
:


Imagine what 2 meters of coax with a capacity of 200pF ( a "load" of
about 200 ohms at 4 MHz) does to a high impedance (several kOhms at
4MHz) antenna connection: right... almost short circuit it to ground.
NEVER use coax between the ATU and the antenna.


That's just about as bad as neatly tywrapping the wire from the tuner to
the bottom insulator on the backstay to the grounded backstay part UNDER
the bottom insulator. Trying to get them to let that wire HANG away from
everything to lower the capacitance to ground is like trying to get 5200
adhesive that's hardened out of a crack in the decking. They don't care
what it does to the signal output, as long as it looks "neat and tidy".

Larry W4CSC

In article ,
"Doug Dotson" wrote:

Normally, when tywrapping the feedline to the backstay below
the insulator, the lower part of the backstay is not grounded. Otherwise
small standoff are used.

Doug. k3qt
s/v Callista

"Larry W4CSC" wrote in message
...
"Meindert Sprang" wrote in
:


Imagine what 2 meters of coax with a capacity of 200pF ( a "load" of
about 200 ohms at 4 MHz) does to a high impedance (several kOhms at
4MHz) antenna connection: right... almost short circuit it to ground.
NEVER use coax between the ATU and the antenna.


That's just about as bad as neatly tywrapping the wire from the tuner to
the bottom insulator on the backstay to the grounded backstay part UNDER
the bottom insulator. Trying to get them to let that wire HANG away from
everything to lower the capacitance to ground is like trying to get 5200
adhesive that's hardened out of a crack in the decking. They don't care
what it does to the signal output, as long as it looks "neat and tidy".

Larry W4CSC




I liked the idea, I saw here a while back, of using the new Kevlar based
Backstay material, and not worring about having to ground or not. Seemed
like the logical answer to me. Then just helical wrap the antenna wire
around the Kevlar Backstay and have a really nice "Fully Loaded Antenna
with alot of electrical length........


Bruce in alaska
--
add a 2 before @

On Thu, 3 Jun 2004 14:56:44 -0400, "Jack Painter"
wrote:


Bruce, you're making a totally off the wall argument now, with opposite
assumptions that were never asserted or offered by any of the posters to
this thread. Taking your questions literally as you phrased them would
generate a laugh by all, indeed. If a laugh was your intention, we'll all
have a good one. But I doubt that you are confused about skin effect, or why
a faraday cage works, and specifically what would defeat it's protection
(ie: an opening). So if you seriously think that for instance, a c-clamp
applied across an open end of thin walled copper tubing, contacting the
inner and outer wall in it's grip, would apply voltage differently to the
inside versus the outside of this tubing, then it will be easy to explain
your error in thinking. And since I did not make a joke of your obvious
geometry and math errors in determining the surface area of an object, one
which you continue to be confused about, I would suggest that we either: end
the thread if you do not desire pleasant and professional discussion, or,
omitting the snide comments that do not reflect well on the group or it's
interested participants.

Respectfully,

Jack Painter
Virginia Beach, Va



Oh boy! I just got back from vacation and am just now reading this
stuff.

Jack, Bruce and the others are entirely right. I once had a hard time
figuring out why RF would not flow on the inside of a tube too. It
would seem logical that it would do as you say but it doesn't.

Look up "wave guide beyond cutoff". That will answer your question
about why rf dose not flow on the inside of a tube.

It will flow on the inside for only a very short distance from the
opening. Then it gets canceled. This is how many signal generator
attenuater work.
They use a tube of 6 or so inches long with a sliding probe inside fed
from one end. On the other open end is a fixed pickup probe. When the
movable probe is close to the fixed probe on the other end, maximum
signal coupling is obtained. As the other probe is moved away inside
the tube the signal becomes highly attenuated.

It is operating as a wave guide that is much too small for the
frequency involved. If the tube diameter was made large enough to be a
quarter wave length in diameter then the rf would propagate through
it. But that would be in a different mode than the skin effect
conduction being discussed.

By the way did you know that skin effect even comes into play in 60 hz
distribution systems?

Regards
Gary

On Wed, 26 May 2004 11:38:26 -0400, "Jack Painter"
wrote:

"Steve (another one)" wrote in message
...
Dear Folks,

What is the recommended wire to connect my insulated backstay to my
AT-120 tuner ? I see references to GTO15 for this purpose in American
publications, but no-one here in the UK seems to know what GTO15 is.
Could someone please suggest an equivalent, or at least a description !

Also if the ground connection has to be broad copper strip because RF
won't run down a wire like a conventional dc current, how can the
antenna be wire ? Doesn't RF have to run along the cable to the base of
the antenna and then up the antenna wire itself ? I'm confused !

Thanks for your help.

Steve

Steve, you have asked about two distinctly different forms of connection
that require equally different conductors. Additionally, within your
grounding questions there also are two different issues, addressed below:

1. RF feedline from ATU to antenna.

This should be coaxial cable with dialectric and shielding designed for RF.
Never improvise with something such as spark plug wires.

2.(a) Grounding: RF

This does not have to be wide surface area copper, but doing so will not
hurt, and it will allow the combination-use of the RF ground connection to
serve as a lightning protection ground. RF ground does not require a dc-
connection to ground, and is often designed to use capacitive coupling to
ground for sailing vessels and other marine applications where isolation for
galvanic protection is adviseable.

2. (b) Grounding: Lightning protection

Also does not require a dc-connection to ground, but may not use low valued
capacitors such as would be acceptable for RF ground. Lightning protection
DOES require the widest surface area possible, this provides a lower
impedance path to ground. But your radio and auto-tuner and other equipment
are most importantly bonded to each other, and that may be of any standard
braid, #8 wire, etc. Only the single connection of all your bonded equipment
to ship's ground must be of the highest surface area possible. If more than
one connection from bonded equipment to ground must be made, then each of
those connections should be wide surface area conductors.

Hope this helps,

Jack Painter
Virginia Beach, VA



A good lightning ground is also a good RF ground. But a good RF ground
is not always a good lightning ground. (as in the case of elevated
radials)

Most lightning energy is concentrated in the DC to 1 mhz range with
some energy going much higher in frequency. So the ground conductors
and ground system must be treated the same as an RF ground system with
with regard to low impedance leads (large surface area) and, in the
case of lightning, low DC resistance connections. Even a low
resistance connection can develop many thousands of volts across it
with the high current lightning.

An RF ground requires a low impedance conductor as well.

Regards
Gary