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Old March 17th 04, 03:39 PM
Cecil Moore
 
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Jim Leder wrote:
Cecil, OK, it was a TIC, I know that, but how does it 'fool' EZNEC?


It violates the element spacing rules. Very close spacing is not allowed.
I forget the details and stumbled upon it by accident. But that antenna
is really, really a "gain" antenna, radiating a lot more than it's
feedpoint power. :-) I should have waited until April 1.
--
73, Cecil http://www.qsl.net/w5dxp



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Old March 17th 04, 05:52 PM
Jim Leder
 
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Yep, had me scratching my head! Great April fools joke! You should have
saved it.
I looked at your original on your web page and it would be interesting to
try on 30.

"Cecil Moore" wrote in message
...
Jim Leder wrote:
Cecil, OK, it was a TIC, I know that, but how does it 'fool' EZNEC?


It violates the element spacing rules. Very close spacing is not allowed.
I forget the details and stumbled upon it by accident. But that antenna
is really, really a "gain" antenna, radiating a lot more than it's
feedpoint power. :-) I should have waited until April 1.
--
73, Cecil http://www.qsl.net/w5dxp



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Old March 18th 04, 12:52 AM
Old Ed
 
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Hi Cecil, and thanks yet again! Comments below...

"Cecil Moore" wrote in message
...
Old Ed wrote:
1. At what elevation angle X does the monopole show the highest gain,
and what is that gain?


Already answered. If I remember right, it was 0 dBi at 26 degrees.


You quoted the 0 dBi at 26 degrees in an earlier post; but
you did not identify the 26 degrees as the highest-gain angle.


2. What is the "average" gain of the dipole, at elevation angle X,
taken over the full 360 degrees of azimuth, at one-degree
increments?


Please define "average" gain. The reason for using a higher gain antenna
is to increase the gain above an "average" monopole. How about if I just
post the radiation pattern on my web page?

I did provide my definition of average (azimuthal) gain with the question;
but you snipped it out. 8-( Not to worry, I can snip it right back in
again...

"2. What is the "average" gain of the dipole, at elevation angle X, taken
over the full 360 degrees of azimuth, at one-degree increments?
(Note: Gain data points expressed in dB should be converted to
linear powers, the linear powers averaged, and then the average
linear power converted back to dB, of course. To do otherwise
would improperly penalize a lobed pattern (the dipole) that might
have one or two minus infinity dB gain values.)"

I know where I want to QSO to so I turn my 130' dipole broadside to AZ.

3. If you're still on board with all this, it would also be interesting
to know what happens to the elevation angle and gain of the
monopole if the number of radials is kicked up to a large number,
like 64.


It no doubt, goes up. 8 is all I ever installed. Seems to me a waste of
effort to use 32 times the copper that it takes for a dipole and still
not have the gain of a dipole. Incidentally, my 20m-10m dipole is
rotatable.


Well, I wasn't suggesting that you put more real copper in the ground;
I was just hoping you might put some more virtual copper in the model,
to see what happens.

As to quantity of copper (real or virtual), some folks find that wire is
cheaper than tall support masts. Other folks, perhaps with tall trees,
would see different trade-offs.

It's good your 20m-10m dipole is rotatable. Mine isn't. 8-(
But we were discussing the 130 footer, used on 30m.
If you can rotate that one, I'm impressed.

73, Ed

--
73, Cecil http://www.qsl.net/w5dxp





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Old March 18th 04, 02:18 AM
Cecil Moore
 
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Old Ed wrote:
But we were discussing the 130 footer, used on 30m.
If you can rotate that one, I'm impressed.


Actually, I can rotate that 130 ft dipole. I live on a
triangular shaped lot so I can rotate it about 60 degrees
from either end. Presently, I have it oriented so the cloverleaf
lobes point toward the world's land masses on the higher bands.
--
73, Cecil http://www.qsl.net/w5dxp



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Old March 18th 04, 05:41 AM
Old Ed
 
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Ahhh, enigmatic as usual! ;-) But let me guess:

Do you have alternate attachment points for one or both end(s)
of the antenna, and transfer said end(s) manually from one
attachment to the other?

If so, I would probably call the process "limited re-orientation"
or some such, vs. "rotation." But it's your antenna, so you get to
call it whatever you'd like.

And I guess there's no joy on modelling the average gain of
said antenna over azimuth. Oh well, it was a nice thought. 8-(

Good DX es 73, Ed


"Cecil Moore" wrote in message
...
Old Ed wrote:
But we were discussing the 130 footer, used on 30m.
If you can rotate that one, I'm impressed.


Actually, I can rotate that 130 ft dipole. I live on a
triangular shaped lot so I can rotate it about 60 degrees
from either end. Presently, I have it oriented so the cloverleaf
lobes point toward the world's land masses on the higher bands.
--
73, Cecil http://www.qsl.net/w5dxp



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Old March 18th 04, 03:42 PM
Cecil Moore
 
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Old Ed wrote:
Do you have alternate attachment points for one or both end(s)
of the antenna, and transfer said end(s) manually from one
attachment to the other?


I have three poles arranged roughly in a triangle. My antenna has
quick disconnects on each end. It takes maybe three minutes to
rotate the antenna by 60 degrees.

And I guess there's no joy on modelling the average gain of
said antenna over azimuth. Oh well, it was a nice thought. 8-(


I offered to publish the azimuthal radiation pattern so you can
be the one to waste your time adding up 360 gains.
--
73, Cecil http://www.qsl.net/w5dxp



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Old March 18th 04, 06:00 PM
Richard Harrison
 
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Cecil, W5DXP wrote:
"Have you ever actually tried one of those? (20 dBI gain for 200 degrees
of the horizontal, a loop closely coupled for supergain)"

Excellent question.

J.D. Kraus is the leading exponent of the "supergain antenna"(W8JK)
which he warns has a price in low feedpoint impedance, low efficiency,
and reduced bandwidth (higher Q).

Felow author F.E. Terman reiterates Kraus` caveats.

Kraus says the W8JK has a gain of 5.8 dBi. That is pretty good for two
1/2-wave elements and compares with a 3-element Yagi. When you replace
the straifgt elements in a Yagi with loops to make a "quagi" you may
gain about 2 dB. Design it for maximum gain, and you may pick up about 2
more dB. So, with a "supergain quagi" why wouldn`t you expect gain to be
limited tio about 10 dB.

The W8JK pattern is a figure-8 almost like a dipole but it gets 5-6 dBi
gain from reorientation of energy and that is 3-4 dB better than a
dipole. An array of two close-spaced quads will probably be sharper yet.
The W8JK pattern is shown in Fig 71 on page 8-50 of the 19th edition of
the ARRL Antenna Book. It seems to have about 100-degrees of beamwidth
in forward and reverse directions, so that may qualify as 200-degrees.

Best regards, Richard Harrison, KB5WZI

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Old March 18th 04, 06:03 PM
Dan Richardson
 
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On Thu, 18 Mar 2004 08:42:03 -0600, Cecil Moore
wrote:

I offered to publish the azimuthal radiation pattern so you can
be the one to waste your time adding up 360 gains.


Cecil,

If you wish you can send me the *.ez file and I'll run it with
MultiNec using the EZNEC engine. As MultiNec is an Excel worksheet it
is very easy to set up an unused cell to give the average gain of a
polar plot.

Or if you wish you can do it youself. MultiNec can be downloaded at:
http://www.qsl.net/ac6la/

73
Danny, K6MHE


  #29   Report Post  
Old March 18th 04, 07:11 PM
Richard Harrison
 
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I attributed the question:
"Have you ever actually ttried one of those?" to Cecil Moore. Mark Keith
asked as a response to Cecil. Sorry for the mistake, but it is an
excellent question that belongs to Mark Keith.

Best regards, Richard Harrison, KB5WZI

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Old March 18th 04, 07:20 PM
Cecil Moore
 
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Richard Harrison wrote:

Cecil, W5DXP wrote:
"Have you ever actually tried one of those? (20 dBI gain for 200 degrees
of the horizontal, a loop closely coupled for supergain)"

Excellent question.


Richard, my posting was a tongue-in-cheek joke.
That antenna has an efficiency far in excess of 100%.
--
73, Cecil, W5DXP

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