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Old November 3rd 05, 06:27 AM
Richard Clark
 
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Default Antenna gain question

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
Total load loss = 0.001 dB


EZNEC+ ver. 4.0

Vert Yagi in Ring of Sources 11/2/2005 10:21:32 PM

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

Frequency = 70 MHz

Load 1 Voltage = 1.418 V. at 25.9 deg.
Current = 0.1182 A. at 25.9 deg.
Impedance = 12 + J 0 ohms
Power = 0.1676 watts

Total applied power = 2000 watts

Total load power = 0.1676 watts
Total load loss = 0.0 dB


As the Bard would offer, there's many a slip between the cup and the
lip. For a first pass approximation, and for all the potential for
errors (which can now be routed out instead of gummed to death), it
appears that the low gain (directivity) dipole absorbs more power than
the high gain (directivity) yagi.

73's
Richard Clark, KB7QHC
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Old November 3rd 05, 07:47 PM
Jim Kelley
 
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Default Antenna gain question

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
Total load loss = 0.001 dB


EZNEC+ ver. 4.0

Vert Yagi in Ring of Sources 11/2/2005 10:21:32 PM

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

Frequency = 70 MHz

Load 1 Voltage = 1.418 V. at 25.9 deg.
Current = 0.1182 A. at 25.9 deg.
Impedance = 12 + J 0 ohms
Power = 0.1676 watts

Total applied power = 2000 watts

Total load power = 0.1676 watts
Total load loss = 0.0 dB


As the Bard would offer, there's many a slip between the cup and the
lip. For a first pass approximation, and for all the potential for
errors (which can now be routed out instead of gummed to death), it
appears that the low gain (directivity) dipole absorbs more power than
the high gain (directivity) yagi.

73's
Richard Clark, KB7QHC


Hi Richard,

What is the plane of polarization of the ring of sources, and what is
the orientation of the dipole?

73, ac6xg

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Old November 3rd 05, 08:20 PM
Richard Clark
 
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Default Antenna gain question

On Thu, 03 Nov 2005 11:47:21 -0800, Jim Kelley
wrote:

What is the plane of polarization of the ring of sources, and what is
the orientation of the dipole?


Hi Jim,

Vertical in free space (which, of course, has no direction, but we
know what Vertical implies). This also includes the yagi.

73's
Richard Clark, KB7QHC
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Old November 3rd 05, 09:44 PM
Jim Kelley
 
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Default Antenna gain question



Richard Clark wrote:

On Thu, 03 Nov 2005 11:47:21 -0800, Jim Kelley
wrote:


What is the plane of polarization of the ring of sources, and what is
the orientation of the dipole?



Hi Jim,

Vertical in free space (which, of course, has no direction, but we
know what Vertical implies). This also includes the yagi.


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

ac6xg


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Old November 3rd 05, 10:47 PM
Richard Clark
 
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Default Antenna gain question

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


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Old November 3rd 05, 11:13 PM
Jim Kelley
 
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Default Antenna gain question



Richard Clark wrote:

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


It looks like you'd have to use an array of non-coherent sources in
order to get rid of the phase cancellation effects (and really see
what's going on).

Thanks Richard.

ac6xg


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Old November 4th 05, 12:42 AM
Richard Clark
 
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Default Antenna gain question

On Thu, 03 Nov 2005 15:13:53 -0800, Jim Kelley
wrote:

It looks like you'd have to use an array of non-coherent sources in
order to get rid of the phase cancellation effects (and really see
what's going on).


Hi Jim,

Then it would be answering a different problem.

73's
Richard Clark, KB7QHC
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Old November 4th 05, 01:56 AM
Richard Clark
 
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Default Antenna gain question

On Thu, 03 Nov 2005 15:13:53 -0800, Jim Kelley
wrote:
use an array of non-coherent sources


EZNEC+ ver. 4.0

Dipole in Ring of Rnd Sources 11/3/2005 5:39:03 PM

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

Frequency = 70 MHz

Load 1 Voltage = 0.002611 V. at -33.23 deg.
Current = 3.627E-05 A. at -33.23 deg.
Impedance = 72 + J 0 ohms
Power = 9.47E-08 watts

Total applied power = 1364 watts

Total load power = 9.47E-08 watts
Total load loss = 0.0 dB

then moved quarterwave:

EZNEC+ ver. 4.0

Dipole in Ring of Rnd Sources 11/3/2005 5:41:17 PM

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

Frequency = 70 MHz

Load 1 Voltage = 0.00676 V. at -110.1 deg.
Current = 9.389E-05 A. at -110.1 deg.
Impedance = 72 + J 0 ohms
Power = 6.348E-07 watts

Total applied power = 1364 watts

Total load power = 6.348E-07 watts
Total load loss = 0.0 dB

then moved backwards a quarterwave

EZNEC+ ver. 4.0

Dipole in Ring of Rnd Sources 11/3/2005 5:44:52 PM

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

Frequency = 70 MHz

Load 1 Voltage = 0.004604 V. at 29.97 deg.
Current = 6.395E-05 A. at 29.97 deg.
Impedance = 72 + J 0 ohms
Power = 2.944E-07 watts

Total applied power = 1364 watts

Total load power = 2.944E-07 watts
Total load loss = 0.0 dB

EZNEC+ ver. 4.0

Yagi in Ring of Rnd Sources 11/3/2005 5:48:14 PM

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

Frequency = 70 MHz

Load 1 Voltage = 0.07004 V. at 66.62 deg.
Current = 0.005837 A. at 66.62 deg.
Impedance = 12 + J 0 ohms
Power = 0.0004088 watts

Total applied power = 1364 watts

Total load power = 0.0004088 watts
Total load loss = 0.0 dB

moved back halfwave:

EZNEC+ ver. 4.0

Yagi in Ring of Rnd Sources 11/3/2005 5:51:43 PM

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

Frequency = 70 MHz

Load 1 Voltage = 0.09133 V. at -53.63 deg.
Current = 0.007611 A. at -53.63 deg.
Impedance = 12 + J 0 ohms
Power = 0.0006952 watts

Total applied power = 1364 watts

Total load power = 0.0006952 watts
Total load loss = 0.0 dB

(and really see what's going on)


Hmmm, at least 1000 times more response... so what's going on? (aside
from a possibly poor implementation of random). Trying to refine the
sources table with tighter random assignments is positively brutal
under EZNEC's primitive (read no) handling of columnar data.

73's
Richard Clark, KB7QHC
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Old November 5th 05, 01:29 AM
Richard Clark
 
Posts: n/a
Default Antenna gain question

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
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Old November 5th 05, 01:38 PM
Cecil Moore
 
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Default Antenna gain question

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


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