On 9/7/2010 11:52 PM, Art Unwin wrote:

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

Boy, he's getting there fast. I bet he's around for less than 3 weeks
this time.

Any takers?

tom
K0TAR

On Sep 7, 12:22*pm, Roy Lewallen wrote:
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

I know Dan Tam, the SPAWAR engineer in the video. He's a pretty sharp
guy. I hesitate to throw him into the Lions' Den but I will if you
let me watch. :-)

"Sal"

On 9/8/2010 1:03 PM, Cecil Moore wrote:


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

I had a dream last night, billions of angels dancing on the head of a
pin ... it was quite unsettling!

Regards,
JS

On 9/8/2010 8:06 PM, Sal M. Onella wrote:
On Sep 7, 12:22 pm, Roy wrote:

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

I know Dan Tam, the SPAWAR engineer in the video. He's a pretty sharp
guy. I hesitate to throw him into the Lions' Den but I will if you
let me watch. :-)

"Sal"

It's a sad comment on the state of this newsgroup that an objective
statement of what are believed to be facts is taken as "throwing [the
engineer] into the lions' den". It's not my intent at all to impugn the
engineer. Surely he's aware of the efficiency of the "antennas" he's
creating, so either my (and Frank's) calculations are grossly incorrect
or SPAWAR thinks there's a market for such inefficient antennas. It
would be educational to know which of these is the case. It was
interesting that there was no mention in the video of very low
efficiency, but I guess that's to be expected for a promotional piece
produced by a marketing department looking for investors.

Roy Lewallen, W7EL

On 9/8/2010 9:35 PM, Roy Lewallen wrote:

...
It's a sad comment on the state of this newsgroup that an objective
statement of what are believed to be facts is taken as "throwing [the
engineer] into the lions' den". It's not my intent at all to impugn the
engineer. Surely he's aware of the efficiency of the "antennas" he's
creating, so either my (and Frank's) calculations are grossly incorrect
or SPAWAR thinks there's a market for such inefficient antennas. It
would be educational to know which of these is the case. It was
interesting that there was no mention in the video of very low
efficiency, but I guess that's to be expected for a promotional piece
produced by a marketing department looking for investors.

Roy Lewallen, W7EL


Gesus! If it walks like a duck, quacks like a duck, swims like a duck,
smells like a duck, sounds like a duck ... well, you know that one.

Never thought I would hear you say that ... ya' never had a hard time
calling a duck a duck before.

Regards,
JS

On Wed, 08 Sep 2010 21:35:19 -0700, Roy Lewallen
wrote:

so either my (and Frank's) calculations are grossly incorrect
or SPAWAR thinks there's a market for such inefficient antennas.

The point I caught, and apparently was not modeled, was the discussion
of antenna height for any particular band. Albeit, such mention was
fleeting, but it sounded suspiciously like half wave, not quarter wave
dimensions.

Aside from that speculation, power specs for military usage are
appropriate for theater operations, not global communications. When I
taught UHF/VHF in the Navy, 10% efficiency was considered perfectly
acceptable as point-to-point communications was the only expectation
and that was rarely as much as 20 miles at best. Experience teaches
that even that only takes 100s of milliwatts.

73's
Richard Clark, KB7QHC

On 9/8/2010 10:50 PM, Richard Clark wrote:
On Wed, 08 Sep 2010 21:35:19 -0700, Roy
wrote:

so either my (and Frank's) calculations are grossly incorrect
or SPAWAR thinks there's a market for such inefficient antennas.

The point I caught, and apparently was not modeled, was the discussion
of antenna height for any particular band. Albeit, such mention was
fleeting, but it sounded suspiciously like half wave, not quarter wave
dimensions.

Aside from that speculation, power specs for military usage are
appropriate for theater operations, not global communications. When I
taught UHF/VHF in the Navy, 10% efficiency was considered perfectly
acceptable as point-to-point communications was the only expectation
and that was rarely as much as 20 miles at best. Experience teaches
that even that only takes 100s of milliwatts.

73's
Richard Clark, KB7QHC

That's still an order of magnitude better than what this antenna seems
able to do at VHF, although the demonstration clearly showed it to be
adequate for working a local repeater with an HT.

But what about HF, which the video clearly mentions? Is a fraction of a
percent efficiency adequate for typical communication needs? I know that
some military HF use is NVIS, for which a vertical antenna is poorly
suited to begin with, so that probably wouldn't be an application. Are
milliwatts of radiated HF used and useful for theater communications?

Roy Lewallen, W7EL

On 9 sep, 03:21, Roy Lewallen wrote:
On 9/8/2010 10:50 PM, Richard Clark wrote:





On Wed, 08 Sep 2010 21:35:19 -0700, Roy
wrote:

so either my (and Frank's) calculations are grossly incorrect
or SPAWAR thinks there's a market for such inefficient antennas.

The point I caught, and apparently was not modeled, was the discussion
of antenna height for any particular band. *Albeit, such mention was
fleeting, but it sounded suspiciously like half wave, not quarter wave
dimensions.

Aside from that speculation, power specs for military usage are
appropriate for theater operations, not global communications. *When I
taught UHF/VHF in the Navy, 10% efficiency was considered perfectly
acceptable as point-to-point communications was the only expectation
and that was rarely as much as 20 miles at best. *Experience teaches
that even that only takes 100s of milliwatts.

73's
Richard Clark, KB7QHC

That's still an order of magnitude better than what this antenna seems
able to do at VHF, although the demonstration clearly showed it to be
adequate for working a local repeater with an HT.

But what about HF, which the video clearly mentions? Is a fraction of a
percent efficiency adequate for typical communication needs? I know that
some military HF use is NVIS, for which a vertical antenna is poorly
suited to begin with, so that probably wouldn't be an application. Are
milliwatts of radiated HF used and useful for theater communications?

Roy Lewallen, W7EL- Ocultar texto de la cita -

- Mostrar texto de la cita -

What about if you are a whale?

What if you are a firefighter?, you can got a good 160 m portable
antenna in your fire engine! Do you remember the pretty nice
"Frequency" film with Dennis Quaid as W2QYV, an ideal antenna for
him :D

Greetings to all - Miguel Ghezzi - LU6ETJ

On 9/9/2010 7:03 AM, lu6etj wrote:

...
What about if you are a whale?

What if you are a firefighter?, you can got a good 160 m portable
antenna in your fire engine! Do you remember the pretty nice
"Frequency" film with Dennis Quaid as W2QYV, an ideal antenna for
him :D

Greetings to all - Miguel Ghezzi - LU6ETJ

ROFLOL! Good sense of humor man!

And, you are totally correct, firemen expending BIG tax dollars for a
dollar conversation is about right.

Regards,
JS

Having dealt with water streams for a while, I wonder how the stream
is measured, because all streams break up into droplets at some point
well before they appear to do so.
- 'Doc