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

In article ,
(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


Ron, Ron,

Loaded Whips, are just that, wires with a big coil in the middle, that
effectivly lengthen the antenna. They are designed to be 1/4 Wavelength
at the Designed Frequency. ( Morad 2800 & 3400 ect) these can be
resonated as 3/4 Wavelenth at higher HF Frequencies very easily by
adding output shunt capacitance in the tuner. The coil does decouple
the antenna above it at something near 4X Designed Resonance. These
type of antennas have been around in Marine Radio for 50 years, and
Eddie Zanbergen RIP (Chief Engineer @ Morad) designed, built, and sold
them throughout the world, and the properties of Impedance vs Frequency
are well documented for them over the years. After one tunes the old
fixed tuned Antenna Tuners, common in the Marine Radio Service for 20
or 30 years, you get a feel for how they tune and how they work. They
DO tune up very well, and ARE as effecent as any other Marine Antenna
System. Been there, Done that, on hundreds of vessels from 20' to 1200'.


Bruce in alaska
--
add a 2 before @

Wires with a big coil in the middle is what I'm talking about. I guess
this is a semantics thing. I can't get used to calling it a choke cause
in fixed station if we wanted to change freq that much we went out and
threw up another 3 curtain full wave Rhombic. You mobile guys are
strange, you want one antenna to do it all.

Ron

Just can't figure out how to get a Rhombic on a sailboat. We don't expect
one antenna to do it all. I have separate antennas for HF, VHF, TV, GPS,
WX SAT, DGPS, FM, HAM VHF, HAM UHF. If only a single antenna
could do it all.

Doug, k3qt
s/v Callista

"Ron Thornton" wrote in message
...
Wires with a big coil in the middle is what I'm talking about. I guess
this is a semantics thing. I can't get used to calling it a choke cause
in fixed station if we wanted to change freq that much we went out and
threw up another 3 curtain full wave Rhombic. You mobile guys are
strange, you want one antenna to do it all.

Ron

In article ,
(Ron Thornton) wrote:

Wires with a big coil in the middle is what I'm talking about. I guess
this is a semantics thing. I can't get used to calling it a choke cause
in fixed station if we wanted to change freq that much we went out and
threw up another 3 curtain full wave Rhombic. You mobile guys are
strange, you want one antenna to do it all.

Ron


Ron, on a vessel, you ostly only have room for one antenna.....


Bruce in alaska
--
add a 2 before @

In article ,
Gary Schafer wrote:

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


Just a few comments here on this thread.......

Gary is right on in his assesment of the operation of the end feed
loaded antenna. The coil does indeed act as a choke on frequencies
higher than 4XResonant. In the "Old Days" we used Morad 2800 and 3600
loaded whips with 15 to 35 ft of wire below them as antennas in the
MF Frequency Range. They were just great below 5 Mhz, and not half
bad above that as the coil only choked off the upper 102" whip and
the coil itself, and left the bottom 10ft of antenna and 35 Ft of
wire as an antenna for the HF Ranges above 5 Mhz. This 45 Ft of
antenna did just fine as an antenna in those ranges as it would be
tuned (Fixed tuned antenna tuner era) as 3/4 Wavelength at these higher
frequencies. today's autotuners have a similar tuning firmware routine
that adds output Capacitance untill it finds the 3/4 Wavelength point.
They don't do as good of job as a Fixed tuned tuner due to the step size
and the sense circuits, but they will get close, and be fairly effecent.
The trick to make this type of antenna work is to get some wire under
the antenna, so that you have an effective antenna length once the coil
chokes off, as the frequency rises. Most of the North Pacific Fishing
Fleet uses this type of antenna system for MF, and HF, comms.

Bruce in alaska
--
add a 2 before @