On Thu, 03 Nov 2005 13:44:47 -0800, Jim Kelley
wrote:

If you wouldn't mind, try moving your Yagi a half wave forward or reverse.

Moving back one half wave:

EZNEC+ ver. 4.0

Vert Yagi in Ring of Sources 11/3/2005 2:37:02 PM

--------------- LOAD DATA ---------------

Frequency = 70 MHz

Load 1 Voltage = 1.655 V. at -135.94 deg.
Current = 0.1379 A. at -135.94 deg.
Impedance = 12 + J 0 ohms
Power = 0.2283 watts

Total applied power = 2000 watts

Total load power = 0.2283 watts
Total load loss = 0.0 dB


moving it such that its "driven" element is dead center to all
radiators (original configuration had the reflector in dead center):

EZNEC+ ver. 4.0

Vert Yagi in Ring of Sources 11/3/2005 2:40:58 PM

--------------- LOAD DATA ---------------

Frequency = 70 MHz

Load 1 Voltage = 1.584 V. at -22.13 deg.
Current = 0.132 A. at -22.13 deg.
Impedance = 12 + J 0 ohms
Power = 0.2091 watts

Total applied power = 2000 watts

Total load power = 0.2091 watts
Total load loss = 0.0 dB

73's
Richard Clark, KB7QHC

On Wed, 02 Nov 2005 22:27:45 -0800, Richard Clark
wrote:

On Fri, 28 Oct 2005 20:37:07 GMT, Ron wrote:

Assume an incoming rf signal has exactly the same strength in all 3
dimensions i.e., completely omnidirectional. Question: would an
antenna having gain capture any more signal power than a completely
omnidirectional antenna with no gain?

Hi All,

Well, it is time to discard the speculation and let modeling approach
this for an answer that at least offers more than swag.

First we strip away the sphere and solve this in two dimensions. To
do that we simply construct a ring of sources surrounding the
prospective antennas and let the winning design emerge.

EZNEC+ ver. 4.0

Dipole in Ring of Sources 11/2/2005 10:00:48 PM

--------------- LOAD DATA ---------------

Frequency = 70 MHz

Load 1 Voltage = 4.783 V. at 23.52 deg.
Current = 0.06643 A. at 23.52 deg.
Impedance = 72 + J 0 ohms
Power = 0.3177 watts

Total applied power = 2000 watts

Total load power = 0.3177 watts

Taking the determination above as the "standard" I then have
progressed to place an NBS yagi in three space about the center to
obtain its best result.

All such expressions (x,y,z) of the placement of the NBS yagi are with
respect to its "driven" element.

0,0,0 Power = 0.2091 watts
..5,0,0 Power = 0.2198 watts
1,0,0 Power = 0.1429 watts
1.5,0,0 Power = 0.1026 watts
2,0,0 Power = 0.1601 watts
2.5,0,0 Power = 0.2113 watts
3,0,0 Power = 0.1571 watts
3.5,0,0 Power = 0.06028 watts
4,0,0 Power = 0.04128 watts

So, within one quadrant, and over the space of roughly a wavelength,
and at intervals of roughly one eighth wavelength, nothing emerges as
being equal to the "standard" above. Except perhaps a hidden peak
between 0,0,0 and .5,0,0. To investigate this:
..25,0,0 Power = 0.2286 watts
examining further:
..125,0,0 Power = 0.2219 watts
nope, examining further:
..375,0,0 Power = 0.2278 watts
nope, examining further:
..30,0,0 Power = 0.2291 watts
nope, examining further:
..35,0,0 Power = 0.2285 watts
nope, looks like the one before at .30,0,0 is the new sweet spot.

Now, to proceed to investigate the other quadrants to see if there is
symmetry:
-3.5,0,0 Power = 0.03997 watts
0,3.5,0 Power = 0.005925 watts
0,-3.5,0 Power = 0.005859 watts

This last offers that on the Y axis there is a strong symmetry, and
along the X axis there is a moderate symmetry. Now, in regard to both
the X and the Y axis, there is a moderate symmetry. If we were to
look at the fine data attempting to find the peak, we should notice
that the "center" of the antenna lies between the "driven" element and
its reflector. My having chosen the "driven" element as the nominal
center was in error and my guess is that if I re-visited the same
quadrant test above, with that new center at the sweet spot, then we
would find very strong symmetry in all four quadrants. I will add
that the Y axis data supports this due to its strong symmetry that is
relatively immune from the choice of antenna center - at least at this
scale.

Putting that aside, it is enough to suggest that barring an
exquisitely positioned peak of rather a sharp rise, then the yagi
exhibits a poorer response compared to a dipole of approx. 1.4dB.

Others are encouraged to investigate further to reclaim that missing
dB or to put the horns to my error.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
Others are encouraged to investigate further to reclaim that missing
dB or to put the horns to my error.

Of course, you have deviated considerably from the original
infinite number of coherent sources.
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote
Of course, you have deviated considerably from the original
infinite number of coherent sources.

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

You guys sure know how to enjoy yourselves trying to analyse
hypothetical situations.

Without any loss in precision, just imagine an isotropic receiver
surrounded by 6 equal intensity beams focussed upon it. Forget all
about an infinite number of radiators.

Or, better still, forget all about the original exceedingly
ill-defined question by a leg-puller. You have been trolled. You
should be ashamed of yourselves for being taken in by such a question.

By the way, the subject of "antenna gains" is amongst the most
confusing of all old-wives' tales. It's worse than so-called VSWR
measurements on non-existent transmission lines. Or from which ends,
or the middle bit, of a dipole does the radiation occur.
----
Reg.

On Sat, 5 Nov 2005 18:15:30 +0000 (UTC), "Reg Edwards"
wrote:
"Cecil Moore" wrote
Of course, you have deviated considerably from the original
infinite number of coherent sources.
You guys sure know how to enjoy yourselves trying to analyse
hypothetical situations.

So now there are at least two of you who can't find the "missing"
power. Kelvinator is winding up a pitch to bounce another piece of
chalk off your noggin, Reg. Fumbling what-ifs and nary a number from
anyone.
"WORK?!?" [with apologies to Maynard G. (for Walter) Krebs, rip].

Or, better still, forget all about the original exceedingly
ill-defined question by a leg-puller. You have been trolled. You
should be ashamed of yourselves for being taken in by such a question.

Hello Reg,

I wrote the original question. It may be dumb but it was not
facetious. I am not a troll.

Happy birthday,

Ron, W4TQT

Richard Clark wrote:

EZNEC+ ver. 4.0

Dipole in Ring of Sources 11/2/2005 10:00:48 PM

--------------- LOAD DATA ---------------

Frequency = 70 MHz

Load 1 Voltage = 4.783 V. at 23.52 deg.
Current = 0.06643 A. at 23.52 deg.
Impedance = 72 + J 0 ohms
Power = 0.3177 watts

Total applied power = 2000 watts

Total load power = 0.3177 watts


Taking the determination above as the "standard" I then have
progressed to place an NBS yagi in three space about the center to
obtain its best result.

All such expressions (x,y,z) of the placement of the NBS yagi are with
respect to its "driven" element.

0,0,0 Power = 0.2091 watts
.5,0,0 Power = 0.2198 watts
1,0,0 Power = 0.1429 watts
1.5,0,0 Power = 0.1026 watts
2,0,0 Power = 0.1601 watts
2.5,0,0 Power = 0.2113 watts
3,0,0 Power = 0.1571 watts
3.5,0,0 Power = 0.06028 watts
4,0,0 Power = 0.04128 watts

So, within one quadrant, and over the space of roughly a wavelength,
and at intervals of roughly one eighth wavelength, nothing emerges as
being equal to the "standard" above. Except perhaps a hidden peak
between 0,0,0 and .5,0,0. To investigate this:
.25,0,0 Power = 0.2286 watts
examining further:
.125,0,0 Power = 0.2219 watts
nope, examining further:
.375,0,0 Power = 0.2278 watts
nope, examining further:
.30,0,0 Power = 0.2291 watts
nope, examining further:
.35,0,0 Power = 0.2285 watts
nope, looks like the one before at .30,0,0 is the new sweet spot.

Now, to proceed to investigate the other quadrants to see if there is
symmetry:
-3.5,0,0 Power = 0.03997 watts
0,3.5,0 Power = 0.005925 watts
0,-3.5,0 Power = 0.005859 watts

This last offers that on the Y axis there is a strong symmetry, and
along the X axis there is a moderate symmetry. Now, in regard to both
the X and the Y axis, there is a moderate symmetry. If we were to
look at the fine data attempting to find the peak, we should notice
that the "center" of the antenna lies between the "driven" element and
its reflector. My having chosen the "driven" element as the nominal
center was in error and my guess is that if I re-visited the same
quadrant test above, with that new center at the sweet spot, then we
would find very strong symmetry in all four quadrants. I will add
that the Y axis data supports this due to its strong symmetry that is
relatively immune from the choice of antenna center - at least at this
scale.

Putting that aside, it is enough to suggest that barring an
exquisitely positioned peak of rather a sharp rise, then the yagi
exhibits a poorer response compared to a dipole of approx. 1.4dB.

Others are encouraged to investigate further to reclaim that missing
dB or to put the horns to my error.

73's
Richard Clark, KB7QHC

Hi Richard,

I think what you're seeing is the 3-D interference pattern generated by
your sources. I'm not sure that really tells us very much about the
antennas themselves. You'd need to surround each of the antennas with a
uniform field in order to compare them. By uniform, I mean the field
intensity toward the antenna is the same in any direction.

Thanks, AC6XG

Jim Kelley wrote:
I think what you're seeing is the 3-D interference pattern generated by
your sources.

Richard is not trying to superpose powers again, is he? :-)
--
73, Cecil http://www.qsl.net/w5dxp

Jim Kelley wrote:

Hi Richard,

I think what you're seeing is the 3-D interference pattern generated by
your sources. I'm not sure that really tells us very much about the
antennas themselves. You'd need to surround each of the antennas with a
uniform field in order to compare them. By uniform, I mean the field
intensity toward the antenna is the same in any direction.

How about polarization?

Roy Lewallen, W7EL

Roy Lewallen wrote:

Jim Kelley wrote:


Hi Richard,

I think what you're seeing is the 3-D interference pattern generated
by your sources. I'm not sure that really tells us very much about
the antennas themselves. You'd need to surround each of the antennas
with a uniform field in order to compare them. By uniform, I mean the
field intensity toward the antenna is the same in any direction.


How about polarization?

Roy Lewallen, W7EL

Hi Roy,

Your guess is better than mine. I think in order not to bias the
results, the solution would have to be that each source is randomly
polarized, i.e. the Sun redshifted down into the radio spectrum - coming
from every direction. The ring of point sources is an interesting
approach. One could use rings at some number of elevation angles, both
above and below the plane of the antennas. The greater the elevation
angle, the smaller the diameter of the ring such that the radial
distance to the antenna is kept constant. But I imgaine you have ideas
of your own in this regard.

73, ac6xg