On 9/6/2010 5:06 PM, Frank wrote:

On 7 MHz a dipole constructed of salt water: Er = 81,
conductivity 5 S/m, and 0.5" diameter has a free
space efficiency of 0.08%. i.e. with 100 W input
the total radiated power = 80 mW.

Frank
(VE6CB)

That looked so bad I had to run an analysis to see for myself. Sure
enough, it's that bad. And even with a 0.25 inch diameter column at 146
MHz, the efficiency is only on the order of 1%. A foot and a half of
wire vs. a pump, power source, and ferrite transformer? No contest.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...
On 9/6/2010 5:06 PM, Frank wrote:

On 7 MHz a dipole constructed of salt water: Er = 81,
conductivity 5 S/m, and 0.5" diameter has a free
space efficiency of 0.08%. i.e. with 100 W input
the total radiated power = 80 mW.

Frank
(VE6CB)

That looked so bad I had to run an analysis to see for myself. Sure
enough, it's that bad. And even with a 0.25 inch diameter column at 146
MHz, the efficiency is only on the order of 1%. A foot and a half of wire
vs. a pump, power source, and ferrite transformer? No contest.

Roy Lewallen, W7EL
-
Finally, something to make a T2FD look good
Wayne W5GIE

On Sep 6, 11:41*pm, Art Unwin wrote:
On Sep 6, 2:00*pm, Roy Lewallen wrote:

On 9/6/2010 8:59 AM, K1TTT wrote:

magnetic coupling to the stream seems kind of odd, but it appears to
work for him. *i wonder what happens if you go qro? *i would expect
some heating of the water and maybe even some ionization or corona
that might cause instability in the stream. *i would also guess the
tuning would be difficult in high winds.

Wind would seem to be a weak point. The top of the conductive stream
would dissipate at different heights depending on the wind velocity, so
a gusty wind would be constantly altering the effective antenna length.

Roy Lewallen, W7EL

Part of the speal given talked about the scarecity of real estate for
the many antennas on ships! Why don't they use non frequency dependent
antennas so antennas can be shared, especially when in combat? And
what do submarines use for antennas
when in the stealth mode?

i would tell you, but then i would have to kill you!

K1TTT wrote:
On Sep 6, 11:41 pm, Art Unwin wrote:
On Sep 6, 2:00 pm, Roy Lewallen wrote:

On 9/6/2010 8:59 AM, K1TTT wrote:
magnetic coupling to the stream seems kind of odd, but it appears to
work for him. i wonder what happens if you go qro? i would expect
some heating of the water and maybe even some ionization or corona
that might cause instability in the stream. i would also guess the
tuning would be difficult in high winds.
Wind would seem to be a weak point. The top of the conductive stream
would dissipate at different heights depending on the wind velocity, so
a gusty wind would be constantly altering the effective antenna length.
Roy Lewallen, W7EL
Part of the speal given talked about the scarecity of real estate for
the many antennas on ships! Why don't they use non frequency dependent
antennas so antennas can be shared, especially when in combat? And
what do submarines use for antennas
when in the stealth mode?

i would tell you, but then i would have to kill you!

Naahhh.. everyone knows they drag an insulated wire, which is why NEC
was updated some years ago to handle insulated wires in a conductive medium.

Now.. when their periscope is up, indeed, there's a lot of special stuff
that goes into shared apertures. Look to the work of Jaumann in WWII..

And with sharing apertures.. it's not so much non-frequency dependent
radiators that is the problem, it's isolation between the Tx and Rx.
Multimegawatt pulses from your radar tend to raise cain with your
sensitive receiver, even if your diplexer does have 100dB isolation.

Finally, it is challenging to make something that can efficiently
radiate at a frequency while not reflecting that same frequency (i.e.
re-radiating). Brings a whole new meaning to "match at the feedpoint"
when your RCS has to be a tiny, tiny fraction of the physical size.
(for reference, the RCS of a resonant dipole with shorted feed is about
0.2 lambda^2)

On Sep 7, 7:03*pm, Jim Lux wrote:
K1TTT wrote:
On Sep 6, 11:41 pm, Art Unwin wrote:
On Sep 6, 2:00 pm, Roy Lewallen wrote:

On 9/6/2010 8:59 AM, K1TTT wrote:
magnetic coupling to the stream seems kind of odd, but it appears to
work for him. *i wonder what happens if you go qro? *i would expect
some heating of the water and maybe even some ionization or corona
that might cause instability in the stream. *i would also guess the
tuning would be difficult in high winds.
Wind would seem to be a weak point. The top of the conductive stream
would dissipate at different heights depending on the wind velocity, so
a gusty wind would be constantly altering the effective antenna length.
Roy Lewallen, W7EL
Part of the speal given talked about the scarecity of real estate for
the many antennas on ships! Why don't they use non frequency dependent
antennas so antennas can be shared, especially when in combat? And
what do submarines use for antennas
when in the stealth mode?

i would tell you, but then i would have to kill you!

Naahhh.. everyone knows they drag an insulated wire, which is why NEC
was updated some years ago to handle insulated wires in a conductive medium.

Now.. when their periscope is up, indeed, there's a lot of special stuff
that goes into shared apertures. *Look to the work of Jaumann in WWII..

And with sharing apertures.. it's not so much non-frequency dependent
radiators that is the problem, it's isolation between the Tx and Rx.
Multimegawatt pulses from your radar tend to raise cain with your
sensitive receiver, even if your diplexer does have 100dB isolation.

Finally, it is challenging to make something that can efficiently
radiate at a frequency while not reflecting that same frequency (i.e.
re-radiating). *Brings a whole new meaning to "match at the feedpoint"
when your RCS has to be a tiny, tiny fraction of the physical size.
(for reference, the RCS of a resonant dipole with shorted feed is about
0.2 lambda^2)

As it happens I bought a nuclear submarine radio transmitter with only
a few hours on it. It is a tube version so I assume the reason that it
saw so little service was when they determined solid state was not an
issue. Just for kicks today I put together 3 rolls of 50 conductor
tape in series without unrolling them so the assembly was about 12
inches tall and 8 inches dia where as the antenna on the tower is
about the size of a bow and arrow target and good for all bands
without being frequency sensitive. Now the quick and dirty one was
really 50 wires in parallel placed in series with end fed on two
outside wires. Now it was only good down to and including 20 metres
while sitting on the table next to the radio in a very cluttered shack
with lots of equipment and on top of that it had no shield so you
can't hang your hat on those results because of proximetry effect and
other short cuts taken and yet the non frequency side of it is fully
evident. So for a submarine or a ship in combat the long wire would
leave an observable trace even when below the surface as the long wire
will rise.
Same goes for ships that have radiators in the double or triple
figures where when damaged control can be transfered to other non
frequency sensitive antennas. I served in the Army so I have little
knoweledge as to what goes on in the Navy and thus the question posed.
Certainly such a antenna would be a lot more stealth like than the
water jet stream proposed on U tube or even a long wire leaving a
trail on the surface for aircraft to zero upon.
Regards
Art

On 9/7/2010 7:04 PM, Art Unwin wrote:
... Just for kicks today I put together 3 rolls of 50 conductor
tape in series without unrolling them so the assembly was about 12
inches tall and 8 inches dia where as the antenna on the tower is
about the size of a bow and arrow target and good for all bands
without being frequency sensitive. ...

Regards
Art

Yeah, but can you shower with it? See, the other antenna doubles as a
shower, just BYOS (Bring Your Own Soap.)

Regards,
JS

On Sep 7, 11:01*pm, John Smith wrote:
On 9/7/2010 7:04 PM, Art Unwin wrote:

... Just for kicks today I put together 3 rolls of 50 conductor
tape in series without unrolling them so the assembly was about 12
inches tall and 8 inches dia where as the antenna on the tower is
about the size of a bow and arrow target and good for all bands
without being frequency sensitive. ...
Regards
Art

Yeah, but can you shower with it? *See, the other antenna doubles as a
shower, just BYOS (Bring Your Own Soap.)

Regards,
JS

John, all non frequency dependent radiators have to be shielded as it
plays havoc with the cancellation of reactance. But even with the
quick lash up I made where I broke all the rules and even changed to
"stacked pancakes" instead of coils inside coils it still would be ok
for directional use in a loft for some of the bands. Either way the
lash up did not totally destroy its attributes. I suppose it would be
more impressive if I shielded it plus a reflector and put it on the
tower but that was not the point I was trying to make which is the
persistance in keeping non frequency dependentcy
while maintaining a small volume. I modeled a ten turn coil inside
another ten turn coil where both were joined together as a closed
circuit and a overall diameter of 8 to 9 inches sitting on a perfect
ground ala reflector When an antenna is not frequency dependent there
is no skin depth resistance because of the Meissner effect so more
current is applied to generating radiation. This conforming to
Maxwell's law by not indulging in generating magnetic fields. Note
Maxwell never added units of Tesla in his equation so why should you?
By the way that model showed gain inbetween 20 and 30 db because of
current bypassing the innards of the radiator and traveling on the
surface.
So the old timers were correct in saying more wire is better....as
long as you decrease the resistance
created by adding wire!!!!!! That way you have
I sq R instead of I sq R + r which is efficiency in radiation to the
maximum.by removing unnecessary losses. Simple concept eh?
Regards
Art

"Roy Lewallen" wrote in message
...
On 9/6/2010 8:59 AM, K1TTT wrote:
magnetic coupling to the stream seems kind of odd, but it appears to
work for him. i wonder what happens if you go qro? i would expect
some heating of the water and maybe even some ionization or corona
that might cause instability in the stream. i would also guess the
tuning would be difficult in high winds.

Wind would seem to be a weak point. The top of the conductive stream would
dissipate at different heights depending on the wind velocity, so a gusty
wind would be constantly altering the effective antenna length.

Roy Lewallen, W7EL

Let's fix the wind problem and shorten the antenna!
Have the water spray up into a receiving vessel the distributes the water
into
5 or 6 radial tubes that make up a capacitive hat. :-)

While we're at it, let's spray out some radials for a counterpoise!

Hey, if we can catch all the water and recirculate it, then we can
add material to increase the conductivity of the water.
ok,ok I'll stop.
MikeK

On 9/8/2010 9:27 AM, amdx wrote:


Let's fix the wind problem and shorten the antenna!
Have the water spray up into a receiving vessel the distributes the water
into
5 or 6 radial tubes that make up a capacitive hat. :-)

While we're at it, let's spray out some radials for a counterpoise!

Hey, if we can catch all the water and recirculate it, then we can
add material to increase the conductivity of the water.
ok,ok I'll stop.
MikeK



Let's just fill a tube with water and provide sufficient heat-sinking to
keep the water at an acceptable temperature. Obviously, the idiot with
the sump pump and walkie-talkie realized the power of the publics'
fondness for toys ...

Regards,
JS

On Sep 7, 2:22*pm, Roy Lewallen wrote:
Sure enough, it's that bad.

How many free electrons exist in ionized water?
--
73, Cecil, w5dxp.com