On Sat, 30 Jul 2005 06:12:33 GMT, Me wrote:

In article .com,
"Skip Gundlach" wrote:

As further background, we have full rails, with the gates combined
electrically with brass straps belowdecks, attached to the arch, the
pushpit and pulpit. We have about 110 lineal feet of 1" SS tube rail,
unless you count the inner rails, plus the arch. In addition we have
the standard 4" copper strapping leading to a sintered bronze Guest
plane below the boat, and also connected to a 3x5' plate under the
workbench top. I think we have a reasonably good ground.

You will never know if you have a "reasonably good ground", unless
you get yourself an Impedance Bridge, and check it at the frequencies
that you commonly work. Anything that is more than 12" away from the
water, isn't going to add "diddley-squat" toward building a Low Impedance
Wideband RF Ground System, /// If
you got a Plastic Hull, you are NEVER going to get a Real RF Ground,
UNLESS the hull builder was smart, (they never are) and put 200+ Sq
Ft of screen under the gellcoat down by the keel. Cellulose hulls
are just as bad, and harder to retrofit that Plastic ones.
Like I said in my first reply, Autotuners were invented to allow any
"Dufus" to think he install an MF/HF Marine Radio System, and save
himself all that money he would have paid a Compitant Radioman.////
Me


Hehe...why don't you tell us what you really think, anonymous poster?

If it takes 200 sq ft of screen under a gel coat to make a good RF
ground, then folks who attempt a similar feat through a hull would
need about 0.5 / 0.05 X 200 sq ft of material - That's 2000 sq ft of
foil or metal mesh (for a 0.05 in gelcoat, and a mere 0.5 inch hull
thickness)

Now THAT would be quite a trick - a square about 100 ft by 20 ft.
Better not tell the folks who use an antenna coupled through a 1/4
inch glass shield - a coupler that can measure 1.5 inch square.
Admitted, this is often for FM radio (say 90 MHz) as opposed to
3MHz (?) on hf. Using these numbers for comparison,
90/3 X 0.5/0.25 X 2.25 sq in = 135 sq in of ground plane, hmmmm that's
1 sq foot in round numbers. Now that *does* look small to me.

I expect the truth lies somewhere between 1 sq ft and 2000 sq ft.
through a half inch hull section. There! How mealy-mouthed is THAT!
:-)

OK, let's get serious: how about locating a bronze through hull,
and connecting a copper foil externally in contact with it.
a square foot THERE, connected internally with good Litz wire might
make a serviceable ground....

Brian Whatcott Altus
p.s A hint for you: talking about "compitant radiomen" makes
prospective customers nervous! :-)

In article ,
Brian Whatcott wrote:

Hehe...why don't you tell us what you really think, anonymous poster?

If it takes 200 sq ft of screen under a gel coat to make a good RF
ground, then folks who attempt a similar feat through a hull would
need about 0.5 / 0.05 X 200 sq ft of material - That's 2000 sq ft of
foil or metal mesh (for a 0.05 in gelcoat, and a mere 0.5 inch hull
thickness)

Now THAT would be quite a trick - a square about 100 ft by 20 ft.
Better not tell the folks who use an antenna coupled through a 1/4
inch glass shield - a coupler that can measure 1.5 inch square.
Admitted, this is often for FM radio (say 90 MHz) as opposed to
3MHz (?) on hf. Using these numbers for comparison,
90/3 X 0.5/0.25 X 2.25 sq in = 135 sq in of ground plane, hmmmm that's
1 sq foot in round numbers. Now that *does* look small to me.

I expect the truth lies somewhere between 1 sq ft and 2000 sq ft.
through a half inch hull section. There! How mealy-mouthed is THAT!
:-)

OK, let's get serious: how about locating a bronze through hull,
and connecting a copper foil externally in contact with it.
a square foot THERE, connected internally with good Litz wire might
make a serviceable ground....

Brian Whatcott Altus
p.s A hint for you: talking about "compitant radiomen" makes
prospective customers nervous! :-)

Nice thought Brian.... However what you seem to forget is that
capacative couping at RF Frequencies, is determined by three things.
1. Area of the Inside the hull Plate.
2. Distance between the two Plates.
3. Conductivity of the Sea Water Plate.

A 200 Sq Ft Screen in the cabin overhead isn't near (Orders of magnitude)
big enough to be an RF Ground for a MF/HF Antenna System, by itself.
Being located far (relative in capactive terms) from the other plate
(Salt water) means that the Rf couping into the water is what, can you
guess? Less than a few Picofarads. Now calculate the RF Impedance for
such a system at ANY, and All MF/HF Marine Frequencies that you like to
use, if you have enough computer power in your supercomputer. then come
back and explain it all to the rest of the world.


Me

You seem to be saying that sea water (which is one heck of a lot less
conductive than copper -- I mean orders of magnitude less conductive) is
the only rf ground (return path) that works? And that the only way to
utilize it in a fiberglass hull is with capacitive coupling?

By your reasoning, radio communication from a vessel on fresh water is
impossible.

Or, as a corollary, radio communication from a vessel on the hard is
impossible because the capacitive coupling to the sea is over a distance
of more than 12".

And of course, for VHF, we all use the equivalent of copper that is not
capacitively coupled to the sea. Since we all agree that VHF works fine
that way, can you tell us at what frequency the laws of electromagnetic
radiation "jump ship" and no longer work the same as at VHF? A reference
would be most welcome. The issue here is radiation, not propagation.

Can you also provide a reference to the published and repeatable testing
of 400 sq. ft. of copper ground that didn't work any better than having
nothing at all? Radio stations thousands of miles from the sea would be
amazed to learn that their ground systems don't work better than nothing
at all.

Why not post your theory on rec.radio.amateur.antenna and see how it is
received there?

Suggest you reef those sails a tad, Me.

Chuck



Me wrote:
In article .com,
"Skip Gundlach" wrote:


As further background, we have full rails, with the gates combined
electrically with brass straps belowdecks, attached to the arch, the
pushpit and pulpit. We have about 110 lineal feet of 1" SS tube rail,
unless you count the inner rails, plus the arch. In addition we have
the standard 4" copper strapping leading to a sintered bronze Guest
plane below the boat, and also connected to a 3x5' plate under the
workbench top. I think we have a reasonably good ground.


You will never know if you have a "reasonably good ground", unless
you get yourself an Impedance Bridge, and check it at the frequencies
that you commonly work. Anything that is more than 12" away from the
water, isn't going to add "diddley-squat" toward building a Low Impedance
Wideband RF Ground System, and anyone who tells you otherwise, is just as
uneducated about MF/HF Marine Radio Antenna Systems, as you seem to be.
I have seen all kinds of Systems that looked very impresive, untill they
were evaluated with real insurmentation. 400 Sq Ft of Copper Screen in
the Cabin Overhead was proffered, as a really good RF Ground, by a well
known Boat Builder, 20 years ago. It didn't work any better than
having nothing at all, when tested, in a real radio enviorment. If
you got a Plastic Hull, you are NEVER going to get a Real RF Ground,
UNLESS the hull builder was smart, (they never are) and put 200+ Sq
Ft of screen under the gellcoat down by the keel. Cellulose hulls
are just as bad, and harder to retrofit that Plastic ones.
Like I said in my first reply, Autotuners were invented to allow any
"Dufus" to think he install an MF/HF Marine Radio System, and save
himself all that money he would have paid a Compitant Radioman.
SGC Autotuners are some of the worst of the lot, even if they did steal
the design from the real inventers. SGC couldn't even copy the design
correctly, and "Old PeeAir" couldn't design his way out of a "Wet Paper
Bag".

Me

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

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

"chuck" wrote in message
ink.net...
You seem to be saying that sea water (which is one heck of a lot less
conductive than copper -- I mean orders of magnitude less conductive) is
the only rf ground (return path) that works? And that the only way to
utilize it in a fiberglass hull is with capacitive coupling?

By your reasoning, radio communication from a vessel on fresh water is
impossible.

Or, as a corollary, radio communication from a vessel on the hard is
impossible because the capacitive coupling to the sea is over a distance
of more than 12".

And of course, for VHF, we all use the equivalent of copper that is not
capacitively coupled to the sea. Since we all agree that VHF works fine
that way, can you tell us at what frequency the laws of electromagnetic
radiation "jump ship" and no longer work the same as at VHF? A reference
would be most welcome. The issue here is radiation, not propagation.

Can you also provide a reference to the published and repeatable testing
of 400 sq. ft. of copper ground that didn't work any better than having
nothing at all? Radio stations thousands of miles from the sea would be
amazed to learn that their ground systems don't work better than nothing
at all.

Why not post your theory on rec.radio.amateur.antenna and see how it is
received there?

Suggest you reef those sails a tad, Me.

Chuck



Me wrote:
In article .com,
"Skip Gundlach" wrote:


As further background, we have full rails, with the gates combined
electrically with brass straps belowdecks, attached to the arch, the
pushpit and pulpit. We have about 110 lineal feet of 1" SS tube rail,
unless you count the inner rails, plus the arch. In addition we have
the standard 4" copper strapping leading to a sintered bronze Guest
plane below the boat, and also connected to a 3x5' plate under the
workbench top. I think we have a reasonably good ground.


You will never know if you have a "reasonably good ground", unless
you get yourself an Impedance Bridge, and check it at the frequencies
that you commonly work. Anything that is more than 12" away from the
water, isn't going to add "diddley-squat" toward building a Low Impedance
Wideband RF Ground System, and anyone who tells you otherwise, is just as
uneducated about MF/HF Marine Radio Antenna Systems, as you seem to be.
I have seen all kinds of Systems that looked very impresive, untill they
were evaluated with real insurmentation. 400 Sq Ft of Copper Screen in
the Cabin Overhead was proffered, as a really good RF Ground, by a well
known Boat Builder, 20 years ago. It didn't work any better than
having nothing at all, when tested, in a real radio enviorment. If
you got a Plastic Hull, you are NEVER going to get a Real RF Ground,
UNLESS the hull builder was smart, (they never are) and put 200+ Sq
Ft of screen under the gellcoat down by the keel. Cellulose hulls
are just as bad, and harder to retrofit that Plastic ones. Like I said
in my first reply, Autotuners were invented to allow any "Dufus" to think
he install an MF/HF Marine Radio System, and save himself all that money
he would have paid a Compitant Radioman.
SGC Autotuners are some of the worst of the lot, even if they did steal
the design from the real inventers. SGC couldn't even copy the design
correctly, and "Old PeeAir" couldn't design his way out of a "Wet Paper
Bag".

Me

In article . net,
chuck wrote:

You seem to be saying that sea water (which is one heck of a lot less
conductive than copper -- I mean orders of magnitude less conductive) is
the only rf ground (return path) that works? And that the only way to
utilize it in a fiberglass hull is with capacitive coupling?

By your reasoning, radio communication from a vessel on fresh water is
impossible.

Or, as a corollary, radio communication from a vessel on the hard is
impossible because the capacitive coupling to the sea is over a distance
of more than 12".

And of course, for VHF, we all use the equivalent of copper that is not
capacitively coupled to the sea. Since we all agree that VHF works fine
that way, can you tell us at what frequency the laws of electromagnetic
radiation "jump ship" and no longer work the same as at VHF? A reference
would be most welcome. The issue here is radiation, not propagation.

Can you also provide a reference to the published and repeatable testing
of 400 sq. ft. of copper ground that didn't work any better than having
nothing at all? Radio stations thousands of miles from the sea would be
amazed to learn that their ground systems don't work better than nothing
at all.

Why not post your theory on rec.radio.amateur.antenna and see how it is
received there?

Suggest you reef those sails a tad, Me.

Chuck

Well Chuck, now lets look at the subject a bit and see what the
difference is between your VHF analogy, and MF/HF RF Ground systems.

Copper vs Salt Water at VHF....Very significant difference in
conductivity, but it isn't conductivity that we are dealing with here.
At VHF the RF Ground side of the antenna is built into the antenna,
and needs only to be .5 meters long. (roughly) Also consider that at VHF
an antenna can operate over a very wide Frequency Range (155-159 Mhz)
without any major RF Impedance changes. This is NOT even close to being
true at MF/HF frequencies. Move your frequency 250Khz and your antenna
tuning is totally blown away.

Copper vs Salt Water at MF/HF.....Still some what significant in
Conductivity, but again it isn't conductivity we are talking about here.
When was the last time you saw a vessel dragging around a pile of copper
so as to have a Good RF Ground, no matter what the hull was made of?
At MF/HF Frequencies the RF Impedance of the Ground System is inversely
proportional to coupling to the Salt water, if the vessel is floating in
salt water. Obviously you have never tried to communicate using MF/HF
Frequencies in the Great Lakes and Mississippi River Systems from
plastic or wood hulled vessels. It is a bitch to design an effective RF
Ground for such vessels, as there just isn't enough there to make it
work, like in Salt Water. Also remember that RF Impedance changes with
Frequency, a rather LARGE point to be made here. When you are designing
a Marine RF Ground system it must work across one order of magnitude, or
better in frequency span, and provide a Low Impedance across the whole
span. Now tell us all just how you accomplish this feat of magic with
a plastic or cellulose hull sitting in fresh water? Like I said, it is
a bitch, and a compromise in the best situation.

The Laws of Physics aren't the problem here, it is how the Frequency
interacts with RF Ground System Impedance that determine how well things
work. No "Jump ship" about it, just simple Physics, that you apparently
don't have a good handle on.

Radio Stations in the MF Frequency Band use Marconi Antennas, and or
Phased Marconi Antennas, for Transmission. These have EXTENSIVE
RF Ground Systems, usually made up of over 100 1/4 Lambda length radial
wires buried 6 to 10" below the surrounding surface, depending on the
Radiation Pattern for that station, as designated on the License issued
by the FCC. These RF Grounds are engineered specifically for the site
and Radiation Pattern needed. The RF Ground for such Systems covers
significantly more area than 400 Sq Ft, and the addition of such a small
area of copper screen, wouldn't make any significant difference to the
Impedance of such a Ground System. What few HF Stations that are
licensed in the US these days, mostly use Balanced Antennas instead of
Marconi Antennas and the RF Ground isn't nearly as significant to their
operation as it is for Marconi Antennas. The significance is basically
limited to Takeoff Angles. Also of some significance here is that all
these situations are single frequency antennas, and therefor don't need
to be Low Impedance across a wide spread of frequencies (an order of
magnitude or better when opertional. If you had some practical knowledge
in the field, you would notice that if a wet, swampy field, or marshland
could be found, that is where these antenna systems are built. Can you
guess why?

Having been in both the Bradcast Engineering, and Marine Radio
Engineering end of things for MANY years, and having designed, installed,
and maintained both classes of systems, I have dealt with these issues
for MANY years, and the moral to the story IS, " It's the RF Ground,
Sonny, the RF Ground".

Me been there, done that......for a long long time.....

In article ,
Me wrote:

In article .com,
"Skip Gundlach" wrote:

As further background, we have full rails, with the gates combined
electrically with brass straps belowdecks, attached to the arch, the
pushpit and pulpit. We have about 110 lineal feet of 1" SS tube rail,
unless you count the inner rails, plus the arch. In addition we have
the standard 4" copper strapping leading to a sintered bronze Guest
plane below the boat, and also connected to a 3x5' plate under the
workbench top. I think we have a reasonably good ground.

You will never know if you have a "reasonably good ground", unless
you get yourself an Impedance Bridge, and check it at the frequencies
that you commonly work. Anything that is more than 12" away from the
water, isn't going to add "diddley-squat" toward building a Low Impedance
Wideband RF Ground System, and anyone who tells you otherwise, is just as
uneducated about MF/HF Marine Radio Antenna Systems, as you seem to be.
I have seen all kinds of Systems that looked very impresive, untill they
were evaluated with real insurmentation. 400 Sq Ft of Copper Screen in
the Cabin Overhead was proffered, as a really good RF Ground, by a well
known Boat Builder, 20 years ago. It didn't work any better than
having nothing at all, when tested, in a real radio enviorment. If
you got a Plastic Hull, you are NEVER going to get a Real RF Ground,
UNLESS the hull builder was smart, (they never are) and put 200+ Sq
Ft of screen under the gellcoat down by the keel. Cellulose hulls
are just as bad, and harder to retrofit that Plastic ones.
Like I said in my first reply, Autotuners were invented to allow any
"Dufus" to think he install an MF/HF Marine Radio System, and save
himself all that money he would have paid a Compitant Radioman.
SGC Autotuners are some of the worst of the lot, even if they did steal
the design from the real inventers. SGC couldn't even copy the design
correctly, and "Old PeeAir" couldn't design his way out of a "Wet Paper
Bag".

Me

Geeze Louise "Me" give the guy a break...... He was just asking for
an opinion....


Bruce in alaska
--
add a 2 before @

Well Bruce/Me, I think you need to pull your two "selves" together!

Sifting through the humorous postings, I think your bottom line is that
HF/MF vertical antennas will not work well (sometimes I think you mean
will not work at all) unless they are (1) over sal****er with a return
path capacitively coupled to the sea (at least for nonmetallic vessels);
or (2) over land with 100 quarter-wave radials in marshland.

You have labored to persuade us that less-than-perfect marine RF ground
systems are certain to disappoint.

It will surprise you, perhaps, to learn that there are many thousands of
vertical HF and MF transmitting antennas in operation in the world today
that satisfy none of those conditions, and yet enable effective
communications activities. Some on land and some over water. These
installations are supported by rigorous theory as well as by on-the-air
performance data.

If you would like to learn more about how this is being done, often with
losses of only a few dB below ideal conditions, drop in at
rec.amateur.radio.antenna and "read the mail." You'll find some
bombastic assertions and opinions to be sure, but also many reasoned
analyses and even quantitative experiments. Hope to see you there, Bruce.

Regards,

Chuck







Bruce in Alaska wrote:
In article ,
Me wrote:


In article .com,
"Skip Gundlach" wrote:


As further background, we have full rails, with the gates combined
electrically with brass straps belowdecks, attached to the arch, the
pushpit and pulpit. We have about 110 lineal feet of 1" SS tube rail,
unless you count the inner rails, plus the arch. In addition we have
the standard 4" copper strapping leading to a sintered bronze Guest
plane below the boat, and also connected to a 3x5' plate under the
workbench top. I think we have a reasonably good ground.

You will never know if you have a "reasonably good ground", unless
you get yourself an Impedance Bridge, and check it at the frequencies
that you commonly work. Anything that is more than 12" away from the
water, isn't going to add "diddley-squat" toward building a Low Impedance
Wideband RF Ground System, and anyone who tells you otherwise, is just as
uneducated about MF/HF Marine Radio Antenna Systems, as you seem to be.
I have seen all kinds of Systems that looked very impresive, untill they
were evaluated with real insurmentation. 400 Sq Ft of Copper Screen in
the Cabin Overhead was proffered, as a really good RF Ground, by a well
known Boat Builder, 20 years ago. It didn't work any better than
having nothing at all, when tested, in a real radio enviorment. If
you got a Plastic Hull, you are NEVER going to get a Real RF Ground,
UNLESS the hull builder was smart, (they never are) and put 200+ Sq
Ft of screen under the gellcoat down by the keel. Cellulose hulls
are just as bad, and harder to retrofit that Plastic ones.
Like I said in my first reply, Autotuners were invented to allow any
"Dufus" to think he install an MF/HF Marine Radio System, and save
himself all that money he would have paid a Compitant Radioman.
SGC Autotuners are some of the worst of the lot, even if they did steal
the design from the real inventers. SGC couldn't even copy the design
correctly, and "Old PeeAir" couldn't design his way out of a "Wet Paper
Bag".

Me


Geeze Louise "Me" give the guy a break...... He was just asking for
an opinion....


Bruce in alaska

On Sat, 30 Jul 2005 18:41:54 GMT, Bruce in Alaska
wrote:


Geeze Louise "Me" give the guy a break...... He was just asking for
an opinion....


Bruce in alaska

Hehe...a blow hard is not silenced quite that easily!

:-)

Brian W

Me wrote in news:Me-
:

SGC Autotuners are some of the worst of the lot, even if they did steal
the design from the real inventers. SGC couldn't even copy the design
correctly, and "Old PeeAir" couldn't design his way out of a "Wet Paper
Bag".

Me



Hee hee....Don't hold back, Skip! Tell us what you REALLY think of SGC's
crapware!....(c;

REAL tuners are manually operated and say Nye-Viking on the front of them.
I own the 3KW model from the 60's. Wet noodles explode above 500
watts!...(c;

You can tell if your ground is poor on big ham transmitters. You hear
screaming when you whistle, briefly, into the metal microphone...as your
hands burn in effigy.

73 DE W4CSC

--
Larry

http://www.budgetmarine.com/pdf/108.pdf
Ground system.

--
The Road Warrior Hobbit

no -- it's NOT ok to contact this account with services or other
commercial interests


"Skip Gundlach" wrote in message
ups.com...
| Howdy, y'all
|
| As most of you know, we're in an extensive refit. We're finally to
the
| point of addressing the stern of the boat. Most of you know we
added
| an arch, on which we've put wind and solar, satellite, gps and vhf
| antennas, davits, and other goodie-hangers.
|
| Our prior HF antenna location was about midway on the starboard
stern
| side, attached by a standoff to the stern rail, 24" up. Tuner is
very
| close to that location, being mounted on the side of the propane
| locker.
|
| As it turns out, my solar module frame is 1" tube and is in such a
| position as to allow the standoff from my whip to attach to it (much
| more support, of course, being 8' in the air, rather than 2' up,
like
| the rail was before). However, to make that work, I'd have to put
the
| whip centerline, or very close to it. The base would be right next
to
| the chain plate for the aft stay.
|
| The way I've got the aft entry, now, it's not a problem to do that
in
| convenience and use terms. The question is, given that it's
marginally
| closer (don't know that I'd change the end of the cable) to the
tuner,
| is that a good placement? There's no parallel metal anywhere
nearby;
| the closest angle is the back stay, going forward, and, 4'+ away,
the
| arch itself. Everything else is right angles.
|
| So, is that a good location for the whip? I'd expected to have to
put
| it very close to the side of the boat in order to keep it out of the
| way. That would put it close to the arch itself, and some
impediment
| to access to some stuff on that side.
|
| Thanks for any informed opinions :{))
|
| L8R
|
| Skip, refitting as fast as I can in the last two days aboard before
| surgery
|
| Morgan 461 #2
| SV Flying Pig
| http://tinyurl.com/384p2 - The vessel as Tehamana, as we bought her
|
| "Twenty years from now you will be more disappointed by the things
you
| didn't do than by the ones you did do. So throw off the bowlines.
Sail
| away from the safe harbor. Catch the trade winds in your sails.
| Explore.
| Dream. Discover." - Mark Twain
|