Roger,

They way mine is installed is the base is secured to the transom
with a standard mounting, but there is a clamp on the side of the radar
arch that secures the lower portion about 6 feet above the base.
No problems with excessive movement in a seaway. If you don't have
an arch, them perhaps a couple of braces bay do the trick.

Doug
s/v Callista

"Roger" wrote in message
m...
Doug

What is the distance between the base of the antenna and the support
clamp. I only have about 3 ft. Does the antenna bounce around much in
rough seas.

Roger



"Doug Dotson" wrote in message
...
Roger,

We have the 23' whip and it works great. Also have a split
backstay, but since the whip was on the boat when we bought
it, I decided to stick with it. I'm not familiar with the 17' whip
you mention. It would appear to me that you may not be
abot to get good tuning acrosss the bands. The specs for the
tuner say that a 23' minimum length is required if I recall
correctly.

Doug, k3qt
s/v Callista

"Roger" wrote in message
om...
I am installing an Icom 802 ssb with a 140 tuner. I am looking for
advice/experience on the difference in performance between
Shakespeare's 17'6" whip vs. the 23' whip.

I have a sloop with a split backstay and probably will go with a
whip.I only have about 3' between the antenna base and the mounting
clamp on the transom. Insulating the backstay and running the feed
wire along the split (through the bimini) is my second choice.

Gary Schafer wrote in
:

Ok, uncle, you win......

Everything everyone teaches is wrong, including me....

Gary Schafer wrote in
:

Ok, uncle, you win......

Everything everyone teaches is wrong, including me....

On Sat, 24 Apr 2004 21:45:17 GMT, Gary Schafer
wrote:
Your 2' piece of wire has a high capacitive REACTANCE. In order to get
power into it you need an equal inductive reactance (coil) to cancel
the capactive reactance to make it appear resistive.

=============================================

I follow what you are saying but isn't that also the definition of
resonance, i.e., the point where capacitive reactance cancels
inductive reactance?

On Sat, 24 Apr 2004 21:45:17 GMT, Gary Schafer
wrote:
Your 2' piece of wire has a high capacitive REACTANCE. In order to get
power into it you need an equal inductive reactance (coil) to cancel
the capactive reactance to make it appear resistive.

=============================================

I follow what you are saying but isn't that also the definition of
resonance, i.e., the point where capacitive reactance cancels
inductive reactance?

On Sun, 25 Apr 2004 08:56:23 -0400, Wayne.B
wrote:

On Sat, 24 Apr 2004 21:45:17 GMT, Gary Schafer
wrote:
Your 2' piece of wire has a high capacitive REACTANCE. In order to get
power into it you need an equal inductive reactance (coil) to cancel
the capactive reactance to make it appear resistive.

=============================================

I follow what you are saying but isn't that also the definition of
resonance, i.e., the point where capacitive reactance cancels
inductive reactance?


When you cancel the capacitive reactance seen at the bottom of the
antenna with an equal amount of inductive reactance you see a pure
resistance at the other end of the coil (transmitter end). But that
does not change anything in the antenna itself.

The shorter an antenna is (from a quarter wave length) the lower it's
radiation resistance is. If you want to put the same amount of power
into it as you did when it was longer then you must put more current
into it. Just simple ohms law at this point. As long as you are
dealing with pure resistance, which you are when you cancel the
reactance.

However, you can not use simple ohms law when dealing with a
reactance, which is what Larry is trying to do. Yes there will be very
high voltages at the output of the antenna tuner with a short antenna
connected to it. But it is because of the reactance of the coil. That
voltage is not in phase with the current at that point.

Take the example that I posed to Larry about the capacitor and
inductor in series connected to an AC supply. There will be a specific
amount of current flowing in the circuit. You will measure a voltage
across the inductor. That voltage can be much higher than the voltage
from the AC supply. If you multiply that voltage by the circuit
current it will appear as though you have more power in the circuit
than what the AC supply is actually putting out! That looks like free
energy!

You have to take into account the phase shift (also called power
factor) that happens across the inductor.

The same thing happens with the antenna tuner situation.

You can not say "because the voltage is high the current must
therefore be low", like Larry wants to do.

The voltage is high and so is the current. BUT THEY ARE NOT IN PHASE.
There are extremely high currents in the system. The high current in
the coil is what causes I squared R loss (power lose).

In the information in my other post about short antennas, the coil has
a resistance of around 10 ohms and the radiation resistance of the
short antenna was only .3 ohms. So you can see that the coil will suck
up most of the power. That is why a short antenna is less efficient
than a longer one. Not because a short antenna radiates poorer than a
longer one.

An antenna will radiate just as well if it is resonant or not.
Provided you get the same amount of power to it.

The E field and H field of an antenna aren't necessarily the same.
They do balance themselves out as they propagate in free space. Has
nothing to do with how well it radiates.

Regards
Gary

On Sun, 25 Apr 2004 08:56:23 -0400, Wayne.B
wrote:

On Sat, 24 Apr 2004 21:45:17 GMT, Gary Schafer
wrote:
Your 2' piece of wire has a high capacitive REACTANCE. In order to get
power into it you need an equal inductive reactance (coil) to cancel
the capactive reactance to make it appear resistive.

=============================================

I follow what you are saying but isn't that also the definition of
resonance, i.e., the point where capacitive reactance cancels
inductive reactance?


When you cancel the capacitive reactance seen at the bottom of the
antenna with an equal amount of inductive reactance you see a pure
resistance at the other end of the coil (transmitter end). But that
does not change anything in the antenna itself.

The shorter an antenna is (from a quarter wave length) the lower it's
radiation resistance is. If you want to put the same amount of power
into it as you did when it was longer then you must put more current
into it. Just simple ohms law at this point. As long as you are
dealing with pure resistance, which you are when you cancel the
reactance.

However, you can not use simple ohms law when dealing with a
reactance, which is what Larry is trying to do. Yes there will be very
high voltages at the output of the antenna tuner with a short antenna
connected to it. But it is because of the reactance of the coil. That
voltage is not in phase with the current at that point.

Take the example that I posed to Larry about the capacitor and
inductor in series connected to an AC supply. There will be a specific
amount of current flowing in the circuit. You will measure a voltage
across the inductor. That voltage can be much higher than the voltage
from the AC supply. If you multiply that voltage by the circuit
current it will appear as though you have more power in the circuit
than what the AC supply is actually putting out! That looks like free
energy!

You have to take into account the phase shift (also called power
factor) that happens across the inductor.

The same thing happens with the antenna tuner situation.

You can not say "because the voltage is high the current must
therefore be low", like Larry wants to do.

The voltage is high and so is the current. BUT THEY ARE NOT IN PHASE.
There are extremely high currents in the system. The high current in
the coil is what causes I squared R loss (power lose).

In the information in my other post about short antennas, the coil has
a resistance of around 10 ohms and the radiation resistance of the
short antenna was only .3 ohms. So you can see that the coil will suck
up most of the power. That is why a short antenna is less efficient
than a longer one. Not because a short antenna radiates poorer than a
longer one.

An antenna will radiate just as well if it is resonant or not.
Provided you get the same amount of power to it.

The E field and H field of an antenna aren't necessarily the same.
They do balance themselves out as they propagate in free space. Has
nothing to do with how well it radiates.

Regards
Gary

On 24 Apr 2004 04:14:26 -0700, (Roger) wrote:

Larry

Thanks for the informative message. Your suggestion on feeding the
backstay from both chainplates is interesting. Unfortunately I have a
hydraulic backstay tensioner on one leg and a backstay radar mount on
the other. Sooo I guess my alternatives a

running the wire from the tuner along one leg of the split backstay
(with stand-offs) to an insulated backstay

going with a 23 ft whip

BTY - I have already used up one chance on the MMSI code. I registered
by VHF radio with Boat US prior to getting the SSB (thus now needing
an FCC license). The FCC requires an new MMSI code.


Larry W4CSC wrote in message ...

I once moved a radar to a mast mount becuase the newly installed ICOM
M-600 SSB would pick up RF that followed the radar cable back to the
nav station and lock up frequently.

73
Joe
SV Coquina
N3HGB

On 24 Apr 2004 04:14:26 -0700, (Roger) wrote:

Larry

Thanks for the informative message. Your suggestion on feeding the
backstay from both chainplates is interesting. Unfortunately I have a
hydraulic backstay tensioner on one leg and a backstay radar mount on
the other. Sooo I guess my alternatives a

running the wire from the tuner along one leg of the split backstay
(with stand-offs) to an insulated backstay

going with a 23 ft whip

BTY - I have already used up one chance on the MMSI code. I registered
by VHF radio with Boat US prior to getting the SSB (thus now needing
an FCC license). The FCC requires an new MMSI code.


Larry W4CSC wrote in message ...

I once moved a radar to a mast mount becuase the newly installed ICOM
M-600 SSB would pick up RF that followed the radar cable back to the
nav station and lock up frequently.

73
Joe
SV Coquina
N3HGB