In article ,
"Tom Dacon" wrote:

I don't believe there's any need for an
electrical bond, since induction should do the job nicely.


The above doesn't take into account that we are dealing with
impedance in the frequency domain. By not having an good
electrial bond, you induce capacative coupling to additional
surface area for your RF Ground, That means that this coupling is
frequency sensative, and then the RF Grounding System will react
significantly different depending on the frequency being transmitted.
Autotune Antenna Couples have very specific tuning firmware, and this
code doesn't react very well to a highly variable Rg Ground impedance.
They are designed to operate against a FLAT RF Ground Impedance,
and the more bumps in the RF Gropund impedance the harder the tuner
has to work to tune the antenna, and the more phantom, and quirky
Low SWR points that the tuner will find, and lock on to.

Bruce in alaska
--
add a 2 before @

When I could not tune out the ground impedance bumps, I installed a cheap
manual antenna tuner in the ground circuit leg. Then I got perfect
impedance matches at all frequencies into a long ground wire. This was in
addition to the normal automatic antenna tuner for the antenna. Tuning
was simple. Just adjust the ground tuner until the SWR was down to the
lowest you could get.

Larry DeMers



Bruce in Alaska wrote:

In article ,
"Tom Dacon" wrote:

I don't believe there's any need for an
electrical bond, since induction should do the job nicely.

The above doesn't take into account that we are dealing with
impedance in the frequency domain. By not having an good
electrial bond, you induce capacative coupling to additional
surface area for your RF Ground, That means that this coupling is
frequency sensative, and then the RF Grounding System will react
significantly different depending on the frequency being transmitted.
Autotune Antenna Couples have very specific tuning firmware, and this
code doesn't react very well to a highly variable Rg Ground impedance.
They are designed to operate against a FLAT RF Ground Impedance,
and the more bumps in the RF Gropund impedance the harder the tuner
has to work to tune the antenna, and the more phantom, and quirky
Low SWR points that the tuner will find, and lock on to.

Bruce in alaska
--
add a 2 before @

Bare copper will corrode rather quickly. Insulated copper would be
better but the insulation will probably degrade in the UV. Bare SS
would probably be best. I have a split backstay where the split is
fairly high up. I ran a separate antenna from the masthead using
thin SS wire, small insulator at the top. Bottom had a small insulator and
a spring to absorb any mast pumping. Attached it to the radar arch. It
worked well, but not any better than the 23' fiberglass whip mounted to
the transome.

Doug

"maxlynn" wrote in message
news:Ygppb.52870$hp5.43787@fed1read04...
Okay, now that you have given your opinion on Kevlar as a backstay, how
about addressing the original question - i.e., is there any conceptual
problem with wrapping a bare copper wire around it and using it for an
antenna? Has anyone done this?

And, oh by the way, how would you feel about using Kevlar as a substitute
for 1x19 in steering cables? Would it shock you to know that many boats
are
using Kevlar in this highly critical application? And have been doing it
successfully for over ten years now? Use as a backstay is pretty mundane
by comparison. And others have been using it for a similar period as
backstay material. And contrary to what you suggest, the lifetime and
other
properties of Kevlar are well understood.


"Tom Dacon" wrote in message
...
This doesn't address your antenna question specifically, but I have to
say
that the idea of replacing a stainless wire backstay with rope just
creeps
me out. Sure Kevlar, in the appropriate size, could be stronger and
still
lighter than the wire, but its long-term durability raises some
significant
questions. The lifetime of stainless steel 1x19 and rod is well
understood,
as is the response to shock loading; I doubt that the same could be said
for
Kevlar. Your backstay's a pretty important rigging component - I wouldn'
t
be
inclined to screw around with it. You might also consider the long-term
cost
of more frequent replacement of the Kevlar, versus the cost of the wire
and
insulators for about a twenty-year lifetime expectancy of the SS wire
and
insulator combination.

I'm not against Kevlar in standing rigging per se, although I'd be
inclined
to use it in a "supporting role", so to speak. In fact, I'm thinking of
replacing my 7x19 SS wire running backstays on my 41' 3/4-rigged sloop
with
Kevlar the next time I re-rig, not so much to save weight as to keep
down
the chafing on my spreaders when the running backstays are housed at the
after shrouds. I just wouldn't use in in a single-point-of-failure
application such as the backstay.

Tom Dacon


"maxlynn" wrote in message
news:hDVob.49689$hp5.39655@fed1read04...
Okay, here's another question on antenna configuration. I have just
gone
through the pricing out of backstay insulators, and received the
suggestion
that a good, less expensive alternative would be to substitute a
Kevlar
backstay for the rod that I have presently, and wind a piece bare of
wire
around the Kevlar, up to near the masthead as an antenna. It is
significantly less expensive, and the Kevlar has the advantage of
being
stronger and lighter than the wire.

Anyone know of any disadvantages to this approach??


"john s." wrote in message
om...
Glenn Ashmore wrote in message
news:JRxob.119973$sp2.25191@lakeread04...
In the process of laying up the hull I incorporated a couple
hundred
sq.
ft of bronze bug screen to serve as a counterpoise. In addition
two
runs of 2" copper foil run down the center of the hull to the keel
area.
Capacitors between the foil and the keel bolts isolate any DC
from
getting back into the counterpoise. That is probably enough but
as
I
am
installing two aluminum tanks, I wonder how kosher it would be to
tie
them into the counterpoise with more capacitors.

It would add another 14 sq ft of coupling area but would it be
introducing other problems?

Glenn, I think you are overdoing it....I just have a copper strap
from
the ground of the antenna tuner to one keel bolt (external lead
keel)
and when I tested the syste,after installation (in New York), I got
a
55 report from a ham in NW Spain. The only time Herb (Southbound II)
did not hear me loud and clear was because my copper strrap had
become
corroded/
john N2ZOA/MM

In article ,
"Doug Dotson" wrote:

It
worked well, but not any better than the 23' fiberglass whip mounted to
the transome.

At what frequency? All Frequencies? A 23' fiberglass whip is
a VERY short antenna at 2182Khz, and m ost autotuners will not
even get a tuned Indication with such an antenna system.

Bruce in alaska
--
add a 2 before @

In article , Larry Demers
wrote:

When I could not tune out the ground impedance bumps, I installed a cheap
manual antenna tuner in the ground circuit leg. Then I got perfect
impedance matches at all frequencies into a long ground wire. This was in
addition to the normal automatic antenna tuner for the antenna. Tuning
was simple. Just adjust the ground tuner until the SWR was down to the
lowest you could get.

Larry DeMers

If your going to use a manual tuner in the ground system, and have to
readjust it for every large frequency change, why would you not just put
the manual tuner on the antenna and just do manual tuning??? Kind of
redudndent isn't it. The whole point of a autotuner is so that the
operator doen't have to know or understand what the tuner is doing.
That, and so appliance operators could install their own SSB Radio's
systems and cut the Marine Electronics Tech's out of their Installation
Money. Same thing, as when the FCC changed the rules for Radar
Installations, by users, only with many more consequencies.

Bruce in alaska
--
add a 2 before @

Since no one answered your question,,
Yes it would be a problem winding a wire around the line. That is if
you make very many turns of the wire. It will act like a choke to the
RF and only the very bottom part of the "coil" of wire will be
effective as an antenna. The rest of it will be electrically
disconnected as far as the RF is concerned due to the inductance of
the choke that you have made.

This is of course at the higher frequencies. It may work fairly well
at 2182.

The old AM whip antennas that were used on 2 and sometimes on 4 mhz
and not on higher frequencies had a center loading coil wound on them.
This increased their efficiency over just a straight whip and putting
all the loading coil in the antenna tuner. With the coil higher up on
the antenna it provided a little higher feed point impedance and
resulted in a more efficient antenna. This worked well when only 2 and
4 mhz was involved. But when higher frequencies are fed to such an
antenna that loading coil that worked wonders on the low frequencies
acts like a choke at the higher frequencies and effectively
disconnects everything above the coil, including part or most of the
coil. You then have only a very short antenna working for you making
it very inefficient.

You could fasten a straight piece of wire to the kevlar and it should
work fine.

Regards
Gary


On Sat, 1 Nov 2003 13:32:36 -0800, "maxlynn" wrote:

Okay, here's another question on antenna configuration. I have just gone
through the pricing out of backstay insulators, and received the suggestion
that a good, less expensive alternative would be to substitute a Kevlar
backstay for the rod that I have presently, and wind a piece bare of wire
around the Kevlar, up to near the masthead as an antenna. It is
significantly less expensive, and the Kevlar has the advantage of being
stronger and lighter than the wire.

Anyone know of any disadvantages to this approach??


"john s." wrote in message
. com...
Glenn Ashmore wrote in message
news:JRxob.119973$sp2.25191@lakeread04...
In the process of laying up the hull I incorporated a couple hundred sq.
ft of bronze bug screen to serve as a counterpoise. In addition two
runs of 2" copper foil run down the center of the hull to the keel area.
Capacitors between the foil and the keel bolts isolate any DC from
getting back into the counterpoise. That is probably enough but as I am
installing two aluminum tanks, I wonder how kosher it would be to tie
them into the counterpoise with more capacitors.

It would add another 14 sq ft of coupling area but would it be
introducing other problems?

Glenn, I think you are overdoing it....I just have a copper strap from
the ground of the antenna tuner to one keel bolt (external lead keel)
and when I tested the syste,after installation (in New York), I got a
55 report from a ham in NW Spain. The only time Herb (Southbound II)
did not hear me loud and clear was because my copper strrap had become
corroded/
john N2ZOA/MM

The coil in the center of an antenna is not a choke it is just an
inductor that electrically lengthens the antenna. This method is used
well above 2-4 mhz in mobile radio. It is not used much above VHF
because a full wave length is already relatively small.

Ron

The coil in the center of a marine antenna that is designed to be used
on 2 mhz is indeed a choke at anything above 7 mhz or so. It is not
intended to be such but that is what it is when the antenna is used
above its intended range. All of the antenna above the coil is
electrically disconnected from the lower part of the antenna. You
could physically remove that upper portion and notice little if any
difference at higher frequencies.

That is the reason that type of antenna is not used on any system that
operates above 4 mhz. A straight whip (no coil involved) is the only
thing that will work satisfactorily in a multi band system. (trap
antenna being the exception)

Those old antennas with the loading coil in them perform much better
on 2 mhz than the straight whip antenna of the same physical length
but they are very poor on the higher bands as part of the antenna is
not there electrically. It is then a very short antenna at the higher
frequencies.

Regards
Gary



On Thu, 20 Nov 2003 21:37:05 -0500 (EST), (Ron
Thornton) wrote:

The coil in the center of an antenna is not a choke it is just an
inductor that electrically lengthens the antenna. This method is used
well above 2-4 mhz in mobile radio. It is not used much above VHF
because a full wave length is already relatively small.

Ron

Well I guess if I tried to push 30 mhz thru a 2 mhz transmitter you
could call the transmitter a choke too. But in reality it ain't and
the coil in the middle of an antenna ain't either. What you describe as
a choke is a tuning inductor, the choking is an inconsequential behavior
of the tuning at a frequency the antenna was never designed to operate
at.

Ron

If it acts like a choke it must be a choke. :)

Regards
Gary

On Fri, 21 Nov 2003 09:52:46 -0500 (EST), (Ron
Thornton) wrote:

Well I guess if I tried to push 30 mhz thru a 2 mhz transmitter you
could call the transmitter a choke too. But in reality it ain't and
the coil in the middle of an antenna ain't either. What you describe as
a choke is a tuning inductor, the choking is an inconsequential behavior
of the tuning at a frequency the antenna was never designed to operate
at.

Ron