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

As has been mentioned on other posts, GTO15 is basically spark plug wire,
that is, high voltage wire. Looking at mine it seems to have a fairly thick
nylon jacket around the tinned wire core and then a thinner black plastic
outer sheath. I would think you could use high quality spark plug wire,
something with the equivalent of 16 or 22 gauge tinned wire core surrounded
by silicone insulation.
Don't know the answer to your second question.

"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

GTO-15 wire's full name is "Gas Tube Sign and Ignition Cable". It's rated
for 15,000 volts and has a stranded copper 14 gauge (4110 circular mils)
core. It is single conductor, not coax. There are 19 very fine strands if
wire, a layer of high voltage insulation, and an outer covering of sunlight
resistant PVC. It's used for the high voltage portion of neon signs and for
oil burner ignition cable. It also happens to work very well for connecting
an antenna tuner to an insulated backstay.

Spark plug wire has a much lighter duty core and is often not sunlight
resistant. Most spark plug wires don't even have a metal wire core. They use
a resistance material to suppress RF noise. The resistance is usually
anywhere from 1000 to 4000 ohms per foot. You wouldn't want to use this for
antenna lead wire.

Ancor Marine Grade Products sells a 25 foot (7.62 meter) spool of GTO-15 as
part number 150102. If your local marine supplier doesn't carry GTO-15 wire
then check with a neon sign supply house.

Rusty O

PS: As to the second part of your question. There have been very long
'discussions' on this group about antennas and grounds. Mostly name calling
and opinions with very few facts. I don't wish to start another one.

PS: As to the second part of your question. There have been very long
'discussions' on this group about antennas and grounds. Mostly name calling
and opinions with very few facts. I don't wish to start another one.

Well I think most of the arguments and name calling revolved around proper
methods to get an "good" RF ground.
I don't think there is much argument that you need foil for the RF ground
and something like GTO15 for the antenna connection. As to why you need 2
inch wide foil for the ground lead when circular wire works for the antenna
connection, I think that is a basic physics question that someone probably
can answer.

It is possible to get spark plug wire with wire core. Racers do not like
the carbon resistance wire and they don't care about noise on their radios.
I would agree that some extra cover over top of the spark plug wire is
probably a good idea although high quality silicone wire is pretty tough.

"Rusty O" wrote in message
ink.net...
GTO-15 wire's full name is "Gas Tube Sign and Ignition Cable". It's rated
for 15,000 volts and has a stranded copper 14 gauge (4110 circular mils)
core. It is single conductor, not coax. There are 19 very fine strands if
wire, a layer of high voltage insulation, and an outer covering of
sunlight
resistant PVC. It's used for the high voltage portion of neon signs and
for
oil burner ignition cable. It also happens to work very well for
connecting
an antenna tuner to an insulated backstay.

Spark plug wire has a much lighter duty core and is often not sunlight
resistant. Most spark plug wires don't even have a metal wire core. They
use
a resistance material to suppress RF noise. The resistance is usually
anywhere from 1000 to 4000 ohms per foot. You wouldn't want to use this
for
antenna lead wire.

Ancor Marine Grade Products sells a 25 foot (7.62 meter) spool of GTO-15
as
part number 150102. If your local marine supplier doesn't carry GTO-15
wire
then check with a neon sign supply house.

Rusty O

PS: As to the second part of your question. There have been very long
'discussions' on this group about antennas and grounds. Mostly name
calling
and opinions with very few facts. I don't wish to start another one.

Gordon,

Yes, you can get spark plug wire with a real wire core. These days it's not
very common. Like you say, racers use it to get a higher powered spark to
their engine. However, most non-racer's cars today have electronic ignition
systems that require the use of resistance wires. Replacing these wires with
non-resistance wires may actually damage the ignition system.

Rusty O

Make sure that you have the real ignition wire and not the wireless wire
type.

Leanne


"Gordon Wedman" wrote in message
news:jqLsc.17107$SQ2.9150@edtnps89...
As has been mentioned on other posts, GTO15 is basically spark plug wire,
that is, high voltage wire. Looking at mine it seems to have a fairly
thick
nylon jacket around the tinned wire core and then a thinner black plastic
outer sheath. I would think you could use high quality spark plug wire,
something with the equivalent of 16 or 22 gauge tinned wire core
surrounded
by silicone insulation.
Don't know the answer to your second question.

In article ,
"Steve (another one)" wrote:

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


Others have covered the GTO-15 question, very well.

There are a number of reasons that copper strap is used for RF Grounding
in the Maritime Radio Installations. One being, that it is desireable
for the RF Ground to have the lowest possible Impedance at the
transmitted frequency.

Two being, that it is desirable that the surface area of the RF Ground
System be as large as practicable, to maximise coupling to the seawater.

Three being, That RF flows on the surface of the conductor, and more
surface area means lower impedance on the Ground.

The antenna wire isn't supposed to couple into the seawater, but into
the ethos, so it should have the least surface area as can practically
handle the RF Current of the transmitter and be tuned to resonance by
the tuner, and as low of resistance as practicable, so that RF Current
can propagate along it's length.

Bruce in alaska Gary S. can chime in anytime on this.....
--
add a 2 before @

On Wed, 26 May 2004 03:42:24 GMT, Bruce in Alaska
wrote:

In article ,
"Steve (another one)" wrote:

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


Others have covered the GTO-15 question, very well.

There are a number of reasons that copper strap is used for RF Grounding
in the Maritime Radio Installations. One being, that it is desireable
for the RF Ground to have the lowest possible Impedance at the
transmitted frequency.

Two being, that it is desirable that the surface area of the RF Ground
System be as large as practicable, to maximise coupling to the seawater.

Three being, That RF flows on the surface of the conductor, and more
surface area means lower impedance on the Ground.

The antenna wire isn't supposed to couple into the seawater, but into
the ethos, so it should have the least surface area as can practically
handle the RF Current of the transmitter and be tuned to resonance by
the tuner, and as low of resistance as practicable, so that RF Current
can propagate along it's length.

Bruce in alaska Gary S. can chime in anytime on this.....


Hi Bruce,

The diameter of the antenna wire is not too important. Actually the
larger it is the less resistive loss it has and less power will be
wasted in heat. But unless the antenna is significantly shorter than a
quarter wavelength that loss is negligible in the antenna as the
radiation resistance (radiation resistance is where the power goes to
be radiated) is usually much higher than the resistive loss of the
wire.

However in a very short antenna the radiation resistance can be only
an ohm or a few ohms. Then the resistance of the wire would be a
larger percentage and the heat loss would be greater thus warranting a
larger diameter wire.

Otherwise a larger diameter wire has the advantage of greater
bandwidth for given tuner settings. But the difference between #10 and
# 16 would probably not be noticeable.

As you well know, in the case of the ground system as we have said
many times before, it needs to be as short as possible or it becomes
part of the antenna and radiates. "The antenna starts at ground".
Anything above ground is antenna.

Regards
Gary

Gary Schafer wrote in
:


The diameter of the antenna wire is not too important. Actually the
larger it is the less resistive loss it has and less power will be
wasted in heat. But unless the antenna is significantly shorter than a
quarter wavelength that loss is negligible in the antenna as the
radiation resistance (radiation resistance is where the power goes to
be radiated) is usually much higher than the resistive loss of the
wire.

The diameter of the antenna wire is very important in the antenna's
BANDWIDTH. Go by the CG shore station and look at how WIDE the conical
monopole antenna is:
http://www.tpub.com/content/et/14092/css/14092_35.htm
The whole reason for the wide cone of these broadband HF antennas is to
make it look as if the conductor were several FEET across to the RF from
the feedpoint.

Multiple, parallel conductors are also used to increase antenna wire
apparent diameter in broadband rhombic antennas such as:
http://www.smc-comms.com/rhombic_antenna.htm

To quote the text:
"The simple one wire system has a bandwidth of approximately 2: 1, however
SMC have wide experience in the design of this type of antenna and are
able to offer arrays with 1, 2 or 3 wires per leg to give a bandwidth of up
to 4: 1 and, by careful design, gains of 22 dBi are possible."


However in a very short antenna the radiation resistance can be only
an ohm or a few ohms. Then the resistance of the wire would be a
larger percentage and the heat loss would be greater thus warranting a
larger diameter wire.

Huh?? ANY antenna under 1/4 wavelength long exhibits HIGHER and HIGHER
impedance the SHORTER it gets. The first low impedance of a wire antenna
occurs when its radiator (against a ground, artificial or real) is 1/4
wavelength long. A very short antenna, i.e. a 6' whip on the handrail, has
a very HIGH impedance as frequency decreases on the HF band. That's why we
use an L network to match it to 50 ohms....coil in series, cap to ground to
lower its impedance.


Otherwise a larger diameter wire has the advantage of greater
bandwidth for given tuner settings. But the difference between #10 and
# 16 would probably not be noticeable.

True, that's why we use multiple parallel conductors above.

As you well know, in the case of the ground system as we have said
many times before, it needs to be as short as possible or it becomes
part of the antenna and radiates. "The antenna starts at ground".
Anything above ground is antenna.


Actually, in a plastic boat, the radiation from the ground strap is useful
radiation. You've just moved the FEEDPOINT up the radiating element above
the sea. My feedpoint is about 4.8' above ground on Lionheart. It's
signal strength 5, readability 8 in Moscow, Belarus, UAE, Japan, Brazil,
most of Western Europe on 40 meters and 20 meters. Works pretty good!

73, Larry W4CSC

On Wed, 09 Jun 2004 00:00:34 -0000, Larry W4CSC
wrote:

Gary Schafer wrote in
:


The diameter of the antenna wire is not too important. Actually the
larger it is the less resistive loss it has and less power will be
wasted in heat. But unless the antenna is significantly shorter than a
quarter wavelength that loss is negligible in the antenna as the
radiation resistance (radiation resistance is where the power goes to
be radiated) is usually much higher than the resistive loss of the
wire.

The diameter of the antenna wire is very important in the antenna's
BANDWIDTH. Go by the CG shore station and look at how WIDE the conical
monopole antenna is:
http://www.tpub.com/content/et/14092/css/14092_35.htm
The whole reason for the wide cone of these broadband HF antennas is to
make it look as if the conductor were several FEET across to the RF from
the feedpoint.

Multiple, parallel conductors are also used to increase antenna wire
apparent diameter in broadband rhombic antennas such as:
http://www.smc-comms.com/rhombic_antenna.htm

To quote the text:
"The simple one wire system has a bandwidth of approximately 2: 1, however
SMC have wide experience in the design of this type of antenna and are
able to offer arrays with 1, 2 or 3 wires per leg to give a bandwidth of up
to 4: 1 and, by careful design, gains of 22 dBi are possible."


However in a very short antenna the radiation resistance can be only
an ohm or a few ohms. Then the resistance of the wire would be a
larger percentage and the heat loss would be greater thus warranting a
larger diameter wire.

Huh?? ANY antenna under 1/4 wavelength long exhibits HIGHER and HIGHER
impedance the SHORTER it gets. The first low impedance of a wire antenna
occurs when its radiator (against a ground, artificial or real) is 1/4
wavelength long. A very short antenna, i.e. a 6' whip on the handrail, has
a very HIGH impedance as frequency decreases on the HF band. That's why we
use an L network to match it to 50 ohms....coil in series, cap to ground to
lower its impedance.


Otherwise a larger diameter wire has the advantage of greater
bandwidth for given tuner settings. But the difference between #10 and
# 16 would probably not be noticeable.

True, that's why we use multiple parallel conductors above.

As you well know, in the case of the ground system as we have said
many times before, it needs to be as short as possible or it becomes
part of the antenna and radiates. "The antenna starts at ground".
Anything above ground is antenna.


Actually, in a plastic boat, the radiation from the ground strap is useful
radiation. You've just moved the FEEDPOINT up the radiating element above
the sea. My feedpoint is about 4.8' above ground on Lionheart. It's
signal strength 5, readability 8 in Moscow, Belarus, UAE, Japan, Brazil,
most of Western Europe on 40 meters and 20 meters. Works pretty good!

73, Larry W4CSC


Oh oh, here we go again. :)

Remember I said that the radiation resistance drops as the antenna
gets shorter. That is the reason the losses go up with a shorter
antenna. Higher current in the antenna and loading coil means more I
squared R loss.

(radiation resistance is equal to the equivalent resistor that would
dissipate the same amount of power that is being radiated) Lower
radiation resistance requires more current for the same amount of
power verses a higher radiation resistance and less current.

The reactance does indeed get higher the shorter the antenna is. With
an antenna shorter than a quarter wave length as you know it looks
like a capacitor. (capacitive reactance) The less capacitance (shorter
antenna) the higher the reactance. The coil in series provides an
equal but opposite inductive reactance to cancel the capacitive
reactance in the antenna.

That leaves only the radiation resistance to feed power to. The coil
AC resistance (not reactance now)is then effectively in series with
the radiation resistance of the antenna. The same current must flow in
both the antenna and coil losses. While the antenna radiates most of
the power it gets, the coil dissipates power in heat equal to the I
squared R loss in the coil.

The capacitor to ground on the other side of the coil and part of the
coil form an L network to match the impedance to the feed line.

Actually we could say that the L network portion really matches the
radiation resistance plus the coil resistance to the feed line.
Because when the coil reactance and antenna reactance are equal we
have resonance and the only component left is purely resistive.

The high reactance in the antenna causes the voltage to go high. But
there is also a phase shift due to the reactance. So the current is
not in phase with the voltage developed across the reactance. That is
why the voltage is high.

Regards
Gary