In article ,
"Dave Morschhauser" wrote:

All --

Please comment on the following:

What about using copper tubing as an RF ground connection? Since the
current flows on the surface, a tube seems to be the most space efficient
way to get a large surface area. PI*R seems to say that a 1" copper tube
would be as effective as a 3" or so copper foil.

Any thoughts?

Thanks,
Dave.

"Bruce in Alaska" wrote in message
...
In article ulztc.40$Y21.34@lakeread02,
"Jack Painter" wrote:

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

Major snippage



I don't know who taught you your math but 1" cooper tubing doesn't even
come close to the surface area per length of 3" copper foil. It isn't
the DC amps that you need to worry about it is the Impedance of the
connection between the RF Ground System and the Ground stud on the
Antenna Tuner. Lower impedance better Rf Ground. It is the Ground
that makes the Antenna work.

Bruce in alaska
--
add a 2 before @

In article mYIuc.10643$ig5.6123@edtnps89,
"Gordon Wedman" wrote:

Well as I mentioned previously, Icom's printed literature on
antenna/transciever installation recommends grounding the transmitter to the
same ground ("boat ground") as the tuner using foil. Of course the Icom
tech that I contacted about this said not to ground the radio so everyone is
confused about this..................

The only people who seem to be confused are those folks who don't have
much experience in MF/HF Marine Radio Antenna System installation and
design. those of us who have been doing this work for more than 30
years have had this figured out for 28 of them. I know one of the Lead
Engineers @ Icom America in Seattle, and he is a great engineer, but has
very little Field Experience in Antenna System Design. When he used to
work for SEA, he was really good at the design of the CPU's that control
the radio's, but it was the SEA Chief Engineer that had 40 years in the
design of antennas for Maritime Radio uses. Marine Antenna design is
fast becoming a Lost Art.

Bruce in alaska
--
add a 2 before @

In article ,
"Meindert Sprang" wrote:

The best place for grounding is at the ATU. Grounding the TX is not
necessary then. If you only ground the TX, high RF currents will flow on the
outside of the coax from ATU to ground and as a result the coax will radiate
too.

Meindert
PE1GRV

One small caveat that I would make to the above is:

If the RF Ground should prove to be of maginally high in impedance at
the Tx Frequency, then the transmitter, if it is not connected to
that RF Ground by anything but the coax, the transmitter will then be
part of the antenna system, as it will tend to float above the RF Ground
by the impedance at the Antenna Tuners Ground Stud. This can cause the
radio to do very strange things, and on occasion can cause RF Burns
when the operator transmits with the ground connected mic hanger
disc in his palm. Alot more common in, the old days of, fixed tuned
channelized antenna tuners. Autotuners just aren't as efficent at tuning
the antennas as the fixed tuner cannelized tuners.

Bruce in alaska
--
add a 2 before @

"Bruce in Alaska" wrote in message
...
In article ,
"Dave Morschhauser" wrote:

All --

Please comment on the following:

What about using copper tubing as an RF ground connection? Since the
current flows on the surface, a tube seems to be the most space
efficient
way to get a large surface area. PI*R seems to say that a 1" copper
tube
would be as effective as a 3" or so copper foil.

Any thoughts?

Thanks,
Dave.

"Bruce in Alaska" wrote in message
...
In article ulztc.40$Y21.34@lakeread02,
"Jack Painter" wrote:

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

Major snippage



I don't know who taught you your math but 1" cooper tubing doesn't even
come close to the surface area per length of 3" copper foil. It isn't
the DC amps that you need to worry about it is the Impedance of the
connection between the RF Ground System and the Ground stud on the
Antenna Tuner. Lower impedance better Rf Ground. It is the Ground
that makes the Antenna work.

Pi*D is circumference, or Pi2R.

1" pipe exceeds the surface area of 3" strap. As totally impractical as
copper pipe would be as a bonding conductor in almost any application, it
would make an excellent RF ground connection on shore facilities where it
would offer several times the surface area of a solid ground rod half it's
diameter. Copper pipe is commonly filled with conductive salts which leech
through holes in the pipe to maintain high conductivity in ground rod
installations.

Best regards,

Jack Painter
Virginia Beach, Va

"Meindert Sprang" wrote in message
..
Much snippage...
..
Only if you feed the 1/2 in the low impedance point, which is halfway in
the
middel. Since this is impractical on a boat, feed it at the endpoint. But
at
the endpoint of a 1/2 wave, the impedance is very high so you need the
least
capacitance you can get at the antenna feedpoint. So GT15 is ok, but keep
it
1" away from any grounded or other conductive area (like strapping the
GTO15
to the uninsulated lower part of the backstay with tie-raps... BAD
PRACTICE).

Meindert
PE1GRV

Is the 1" just a rule of thumb or is there some engineering calculations to
support this distance? I see many sailboats with 1" varnished wooden dowels
or even plastic hair curlers with cable ties used to keep the GTO15 off the
uninsulated backstay wire. I have a feeling wider spacing would be even
better.Comments please.
Doug K7ABX

"Doug" wrote in message
link.net...

"Meindert Sprang" wrote in message
..
So GT15 is ok, but keep it 1" away from any grounded or other conductive
area (like strapping the
GTO15 to the uninsulated lower part of the backstay with tie-raps... BAD
PRACTICE).

Meindert
PE1GRV

Is the 1" just a rule of thumb or is there some engineering calculations
to
support this distance?

It is more a rule of thumb. At 1" the extra capacity caused by the wire
close to the backstay is low enough not to have any bad influence on the
high impedant line.

Here's some math: two wires, 1 mm in diameter, 25.4mm (1") spaced apart, 1
meter long form a capacitor of 0.35pF, which is hardly noticable at HF
frequencies (15kOhm at 30MHz).
The same wires, 1mm apart, form a capacitor of 9pF. With solid insulation
between them, the capacity goes up by a factor of 2 to 10, depending on the
type of insulation used. Coax, for instance, has a typical capacitance of
100pF/meter.

So 1" is a rule of thumb. For SI minded people, 1cm would probably do fine
too.

Meindert

In article .net,
"Doug" wrote:

"Meindert Sprang" wrote in message
..
Much snippage...
.
Only if you feed the 1/2 in the low impedance point, which is halfway in
the
middel. Since this is impractical on a boat, feed it at the endpoint. But
at
the endpoint of a 1/2 wave, the impedance is very high so you need the
least
capacitance you can get at the antenna feedpoint. So GT15 is ok, but keep
it
1" away from any grounded or other conductive area (like strapping the
GTO15
to the uninsulated lower part of the backstay with tie-raps... BAD
PRACTICE).

Meindert
PE1GRV

Is the 1" just a rule of thumb or is there some engineering calculations to
support this distance? I see many sailboats with 1" varnished wooden dowels
or even plastic hair curlers with cable ties used to keep the GTO15 off the
uninsulated backstay wire. I have a feeling wider spacing would be even
better.Comments please.
Doug K7ABX



The 1" is a "Rule Of Dumb", that does allow for some decoupling, but
doesn't really decouple the antenna for the parallel Grounded backstay.
One can calculate the capacative interaction between the two, or one
can just use the "Rule of Dumb" and let the antenna tuner correct for
the extra capacitance. Just understand that most autotuners will not
like the extra capacitance on the output, and this will tend to widen
out the 1/2 wavelength tuning problems that all endfeed autotuners have.

Bruce in alaska
--
add a 2 before @

In article RI1vc.2576$Y21.814@lakeread02,
"Jack Painter" wrote:

Pi*D is circumference, or Pi2R.

1" pipe exceeds the surface area of 3" strap. As totally impractical as
copper pipe would be as a bonding conductor in almost any application, it
would make an excellent RF ground connection on shore facilities where it
would offer several times the surface area of a solid ground rod half it's
diameter. Copper pipe is commonly filled with conductive salts which leech
through holes in the pipe to maintain high conductivity in ground rod
installations.

Best regards,

Jack Painter
Virginia Beach, Va

Jack my boy you need to go back to school and refresh your geometry.

Pi*D is circumfrence This is true. Now what is the outside surface
area for one inch of length of 1" dia copper pipe?
Lets see 3.1416*1"=3.1416 3.1416*1" length = 3.1416 Square Inches.


Now lets look at 3" copper foil.....ok for Inch of length
we have 3.0 inches square inches of surface area on the front
side and 3.0 square inches of surface area on the back side.
That makes a total of 6 Square Inches of surface area per 1"
of length. We will ignore the thickness of the foil, just because
it isn't significant for the terms we are discussion here.

Now which has more surface area per linear inch?

3.1416 Square Inches for the copper tubing........

or

6 square Inches for the 3" foil........

Hmmmmmmm, wonder what could be the answer.........

If you like, you could think of the copper tubing as being flattened
into a bar and measure it again and it still wouldn't approch a 3" foil
for surface area.

You don't get to include the inside surface area of the tubing, because
RF flows on the outside surface only, but even if you did, you would
still come up a bit short on surface area when compared to 3" copper
foil.

We aren't talking about Shoreside systems on this thread as the original
poster specificly asked about shipboard installations. You observations
about copper pipes being used for Grounding Rods in MF/HF systems
instead of solid copper has some merit, but most RF Grounded Antenna
Systems in the Maritime Mobile Radio Service use a 1/4 Lambda Radial
Grounding System designed for the lowest Frequency that the antenna will
be used on, with interspeced radials cut for 1/4 Lambda at the other
major operating bands. These type antennas really fell out of favor
in the 30's and 40's for Non RF Grounded Antennas like the Rhombics
that Pt. Reyes, CA (KMI) used. They had a set of Phased Rhombics that
could be steered to any point from due South to due North, on 4, 6, 8,
12,16, and 22 Mhz. No Grounding required, and a Frontend smoking signal
everywhere in the Pacific.



Bruce in alaska
--
add a 2 before @

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

Pi*D is circumference, or Pi2R.

1" pipe exceeds the surface area of 3" strap. As totally impractical as
copper pipe would be as a bonding conductor in almost any application,
it
would make an excellent RF ground connection on shore facilities where
it
would offer several times the surface area of a solid ground rod half
it's
diameter. Copper pipe is commonly filled with conductive salts which
leech
through holes in the pipe to maintain high conductivity in ground rod
installations.

Jack my boy you need to go back to school and refresh your geometry.

Pi*D is circumfrence This is true. Now what is the outside surface
area for one inch of length of 1" dia copper pipe?
Lets see 3.1416*1"=3.1416 3.1416*1" length = 3.1416 Square Inches.


Now lets look at 3" copper foil.....ok for Inch of length
we have 3.0 inches square inches of surface area on the front
side and 3.0 square inches of surface area on the back side.
That makes a total of 6 Square Inches of surface area per 1"
of length. We will ignore the thickness of the foil, just because
it isn't significant for the terms we are discussion here.

Now which has more surface area per linear inch?

3.1416 Square Inches for the copper tubing........

or

6 square Inches for the 3" foil........

Hmmmmmmm, wonder what could be the answer.........

If you like, you could think of the copper tubing as being flattened
into a bar and measure it again and it still wouldn't approch a 3" foil
for surface area.

You don't get to include the inside surface area of the tubing, because
RF flows on the outside surface only, but even if you did, you would
still come up a bit short on surface area when compared to 3" copper
foil.

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. 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. We are
talking about a bonded connection that has RF voltages, and during tuning
applications, RF current applied directly to the conductor. Respectfully, my
geometry and description of the conductor skin-effect condition are both
correct, and 1" pipe exceeds the surface area of 3" strap.

Best regards,

Jack Painter
Virginia Beach, Va

"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