Antenna gain question
 

Jim Kelley wrote:
Such a claim might be remotely plausible were it not for the fact that
rotating a directional antenna does not "coherently sum all the rays".

Seems to me, a receiving Yagi causes constructive interference
in the forward direction and destructive interference in the
rearward direction.
--
73, Cecil http://www.qsl.net/w5dxp

Antenna gain question
 

Cecil Moore wrote:

Jim Kelley wrote:

Such a claim might be remotely plausible were it not for the fact that
rotating a directional antenna does not "coherently sum all the rays".


Seems to me, a receiving Yagi causes constructive interference
in the forward direction and destructive interference in the
rearward direction.

But does it seem the antenna causes destructive interference when the
forward direction of the radiation is toward the rearward direction of
the antenna, or does it seem like it causes constructive interference
when the forward direction of the radiation is away from the rearward
direction of the antenna....and if so, what does that have to do with
"coherently summing all the rays by rotating the antenna"? Just wondering.

ac6xg

Antenna gain question
 

Cecil Moore wrote:

Jim Kelley wrote:

... what does that have to do with "coherently summing all the rays by
rotating the antenna"? Just wondering.


"Coherently summing" certainly doesn't imply that interference
is only constructive. An antenna is "coherently summing" all
the rays it receives no matter what direction it is pointed.

And still, rotating the antenna has nothing to do with summing the
signals - coherently, or otherwise. Agreed?

ac6xg

Antenna gain question
 

Jim Kelley wrote:
... what does that have to do with
"coherently summing all the rays by rotating the antenna"? Just wondering.

"Coherently summing" certainly doesn't imply that interference
is only constructive. An antenna is "coherently summing" all
the rays it receives no matter what direction it is pointed.
--
73, Cecil http://www.qsl.net/w5dxp

Antenna gain question
 

Ron wrote:
. . .

An isotropic antenna placed at the focal point would collect all of
the rays whereas a directional antenna at would not.


Therefore, in this particular situation, the isotropic would have
higher gain and capture more power than any directional antenna.

Please correct me if I am wrong.


Not sure what you mean by "focal point", but the best any antenna can do
is to intercept half the energy in some equivalent cross-sectional area
of an impinging field. It does this when connected to a matched load.

When an antenna intercepts one watt from a field having a power density
of one watt per square meter, it's said to have an "effective aperture"
or "capture area" of one square meter. The higher the gain of an antenna
in some particular direction, the larger its effective aperture in that
direction. Consequently, a high gain antenna would "capture" more power
from a wave arriving in its favored direction than an isotropic antenna
would. It would, of course, capture less from other directions, but
assuming equal efficiency, both antennas would capture equal amounts
overall.

The "capture area" isn't some physical region with boundaries -- it's
simply a way of expressing how much power is extracted from a field
having a given power density. In other words, it's just another way of
expressing antenna gain.

Roy Lewallen, W7EL

Antenna gain question
 

On Wed, 02 Nov 2005 00:26:06 GMT, Cecil Moore wrote:

Jim Kelley wrote:
... what does that have to do with
"coherently summing all the rays by rotating the antenna"? Just wondering.

"Coherently summing" certainly doesn't imply that interference
is only constructive. An antenna is "coherently summing" all
the rays it receives no matter what direction it is pointed.

Has someone got a good definition of coherent.

I thought that it implied "same phase", as in a coherent source is one
where all rays, photons, whatever are in phase. An antenna may well
receive rays from a single source that are not in phase.

If that is the case, what is "coherent summing". Is it trying to refer
to a function that adds components algebraically, ie having regard for
the magnitude and phase?

Why is light a better vehicle for explanation of an antenna that radio
waves?

Owen
--

Antenna gain question
 

Owen Duffy wrote:

Has someone got a good definition of coherent.

I thought that it implied "same phase", as in a coherent source is one
where all rays, photons, whatever are in phase. An antenna may well
receive rays from a single source that are not in phase.
. . .

The way I've always seen it used in this context is meaning "exactly the
same frequency". They don't have to be in phase, but the same-frequency
requirement implies that the phase relationship wouldn't change with time.

This is consistent with the definition from _Merriam Webster's
Collegiate Dictionary_: "relating to or composed of waves having a
constant difference in phase ~light".

Roy Lewallen, W7EL

Antenna gain question
 

Roy Lewallen wrote:
Ron wrote:

. . .


An isotropic antenna placed at the focal point would collect all of
the rays whereas a directional antenna at would not.



Therefore, in this particular situation, the isotropic would have
higher gain and capture more power than any directional antenna.

Please correct me if I am wrong.


Not sure what you mean by "focal point", but the best any antenna can do
is to intercept half the energy in some equivalent cross-sectional area
of an impinging field. It does this when connected to a matched load.

I agree.

By "focal point" I meant the center of the sphere where the rays
converge and where the antenna would be located.

When an antenna intercepts one watt from a field having a power density
of one watt per square meter, it's said to have an "effective aperture"
or "capture area" of one square meter. The higher the gain of an antenna
in some particular direction, the larger its effective aperture in that
direction. Consequently, a high gain antenna would "capture" more power
from a wave arriving in its favored direction than an isotropic antenna
would. It would, of course, capture less from other directions, but
assuming equal efficiency, both antennas would capture equal amounts
overall.

In the unusual field defined in my example, the algebraic sum of all
the rays collected by the antenna would be higher in the isotropic
antenna than a high gain antenna. Think of the front to back ratio of
the high gain antenna which would result in very little output from
the rays behind and on the sides of the antenna. Therefore, the
isotropic would have a higher output which is indicative of higher gain.

I do not understand what you mean by "capture equal amounts overall".
Energy which may strike the antenna but does not result in any output
power isn't "captured".

The "capture area" isn't some physical region with boundaries -- it's
simply a way of expressing how much power is extracted from a field
having a given power density. In other words, it's just another way of
expressing antenna gain.

How about a dish antenna? Isn't the capture area proportional to the
physical area of the dish?

Ron, W4TQT

Antenna gain question
 

Jim Kelley wrote:
And still, rotating the antenna has nothing to do with summing the
signals - coherently, or otherwise. Agreed?

Are we talking normal operation or receiving big
bang background radiation?
--
73, Cecil http://www.qsl.net/w5dxp

Antenna gain question
 

Owen Duffy wrote:
Has someone got a good definition of coherent.

From the IEEE Dictionary: "coherent (1)(fiber optics) Characterized by
a fixed phase relationship between points on an electromagnetic wave ...
(2)(laser maser) A light beam is said to be coherent when the electric
vector at any point in it is related to that at any other point by a
definite, continuous sinusoidal function."

An antenna may well
receive rays from a single source that are not in phase.

I receive rays from WTAW that are sometimes in phase and sometimes not
over a period of mere seconds. Earth's atmosphere seems to be a
coherence killer.
--
73, Cecil http://www.qsl.net/w5dxp

Antenna gain question
 

On Wed, 02 Nov 2005 04:30:16 GMT, Cecil Moore wrote:

Owen Duffy wrote:
Has someone got a good definition of coherent.

From the IEEE Dictionary: "coherent (1)(fiber optics) Characterized by
a fixed phase relationship between points on an electromagnetic wave ...
(2)(laser maser) A light beam is said to be coherent when the electric
vector at any point in it is related to that at any other point by a
definite, continuous sinusoidal function."


Thanks Cecil and Roy... obviously my understanding (in-phase) was just
too narrow. I did find Roy's text more coherent!

Interesting to Google for the use of the term, and it appears to be
very loosely used... I guess to some extent because of its roots in
common language and the ordinary meaning of the word.

Owen
--

Antenna gain question
 

On Wed, 02 Nov 2005 03:58:56 GMT, Ron wrote:



In the unusual field defined in my example, the algebraic sum of all
the rays collected by the antenna would be higher in the isotropic
antenna than a high gain antenna. Think of the front to back ratio of
the high gain antenna which would result in very little output from
the rays behind and on the sides of the antenna. Therefore, the
isotropic would have a higher output which is indicative of higher gain.


Is this to rewrite the principle of reciprocity?

Owen
--

Antenna gain question
 

Ron wrote:
In the unusual field defined in my example, the algebraic sum of all the
rays collected by the antenna would be higher in the isotropic antenna
than a high gain antenna.

The same amount of energy is incident upon both antennas at
the center of the sphere. Maybe the high-gain antenna re-
radiates more energy than the isotropic?
--
73, Cecil http://www.qsl.net/w5dxp

Antenna gain question
 

Roy, W7EL wrote:
"They don`t have to be in phase, but the same frequency requirement
implies that the phase relationship wouldn`t change with time."

Definitions of terms like "coherent" change with time.

Slectromagnetic waves are described as "plane-polarized waves" because
variations in their electric and magnetic fields can be represented by
vectors that lie in a plane. It is proven that light waves and radio
waves are of the same sort but differ in frequency.

The first reference I ever saw of a coherent wave was a description of
light from a laser. It meant the waves started and stopped together
passing through zero at the same time.

Light waves are emitted by molecules or atoms that are excited by
thermal or electrical means. These molecules or atoms are randomly
positioned and so are the waves generated by the energy level changes
within them. Phase and polarization are thus random in light produced by
ordinary light sources. Light is coherent from a laser.

A photon can interact with an atom in a laser if its energy exactly
matches the energy difference (delta E) between two allowed (by Bohr)
energy states for the atom, it can cause a transition. This is called a
stimulated transition.

Best regards, Richard Harrison, KB5WZI

Antenna gain question
 

Ron wrote:
. . .
By "focal point" I meant the center of the sphere where the rays
converge and where the antenna would be located.

I have to admit, I was looking at this a more of a problem of equal
signals arriving from all directions, rather than at the middle of some
sort of convergence. Of course, any rays reaching the center would
continue on through, Cecil's unique theories notwithstanding. I don't
have the spare time to contemplate what the end field distribution would
be like at the center of the antenna or its periphery.

When an antenna intercepts one watt from a field having a power density
of one watt per square meter, it's said to have an "effective aperture"
or "capture area" of one square meter. The higher the gain of an antenna
in some particular direction, the larger its effective aperture in that
direction. Consequently, a high gain antenna would "capture" more power
from a wave arriving in its favored direction than an isotropic antenna
would. It would, of course, capture less from other directions, but
assuming equal efficiency, both antennas would capture equal amounts
overall.


In the unusual field defined in my example, the algebraic sum of all the
rays collected by the antenna would be higher in the isotropic antenna
than a high gain antenna.

It's not obvious to me why that would be.

Think of the front to back ratio of the high
gain antenna which would result in very little output from the rays
behind and on the sides of the antenna.

That's true. But the output would be higher in reponse to the rays
arriving from the front. We call that "gain". Another way to express it
is that it intercepts a field from a larger area of the wave front.

Therefore, the isotropic would
have a higher output which is indicative of higher gain.

You're right that higher output means higher gain. I maintain that both
antennas have the same total gain, i.e., the same total interception of
power from all directions. This follows directly from the reciprocity
principle.

I do not understand what you mean by "capture equal amounts overall".
Energy which may strike the antenna but does not result in any output
power isn't "captured".

The field you're creating comes from something and goes somewhere. If
you subtract the total amount going from the total amount generated,
you'll get the amount dissipated in the load connected to the antenna.
That is the amount of energy "captured" or "intercepted" by the antenna.
And that's what I thought you were talking about all along.

The "capture area" isn't some physical region with boundaries -- it's
simply a way of expressing how much power is extracted from a field
having a given power density. In other words, it's just another way of
expressing antenna gain.


How about a dish antenna? Isn't the capture area proportional to the
physical area of the dish?

Indeed it is, in the front direction. But how about a dipole? The
capture area (or gain) broadside to an infinitesimal dipole is just
slightly less than that of a half wavelength dipole. And wire diameter
makes almost no difference.

Sorry, the theoretical construct is just a little too much like
Calvinball to hold my interest. I'll bow out now. Best luck in sorting
it out.

Roy Lewallen, W7EL

Antenna gain question
 

Thanks, Roy for your and everyone's participation. I think I will
bow out here also. Hope all this hasn't been a waste of space.
"Thinking" usually has some value.

Ron W4TQT

Roy Lewallen wrote:
Ron wrote:

. . .
By "focal point" I meant the center of the sphere where the rays
converge and where the antenna would be located.


I have to admit, I was looking at this a more of a problem of equal
signals arriving from all directions, rather than at the middle of some
sort of convergence. Of course, any rays reaching the center would
continue on through, Cecil's unique theories notwithstanding. I don't
have the spare time to contemplate what the end field distribution would
be like at the center of the antenna or its periphery.

When an antenna intercepts one watt from a field having a power density
of one watt per square meter, it's said to have an "effective aperture"
or "capture area" of one square meter. The higher the gain of an antenna
in some particular direction, the larger its effective aperture in that
direction. Consequently, a high gain antenna would "capture" more power
from a wave arriving in its favored direction than an isotropic antenna
would. It would, of course, capture less from other directions, but
assuming equal efficiency, both antennas would capture equal amounts
overall.



In the unusual field defined in my example, the algebraic sum of all
the rays collected by the antenna would be higher in the isotropic
antenna than a high gain antenna.


It's not obvious to me why that would be.

Think of the front to back ratio of the high gain antenna which would
result in very little output from the rays behind and on the sides of
the antenna.


That's true. But the output would be higher in reponse to the rays
arriving from the front. We call that "gain". Another way to express it
is that it intercepts a field from a larger area of the wave front.

Therefore, the isotropic would have a higher output which is
indicative of higher gain.


You're right that higher output means higher gain. I maintain that both
antennas have the same total gain, i.e., the same total interception of
power from all directions. This follows directly from the reciprocity
principle.

I do not understand what you mean by "capture equal amounts overall".
Energy which may strike the antenna but does not result in any output
power isn't "captured".


The field you're creating comes from something and goes somewhere. If
you subtract the total amount going from the total amount generated,
you'll get the amount dissipated in the load connected to the antenna.
That is the amount of energy "captured" or "intercepted" by the antenna.
And that's what I thought you were talking about all along.

The "capture area" isn't some physical region with boundaries -- it's
simply a way of expressing how much power is extracted from a field
having a given power density. In other words, it's just another way
of expressing antenna gain.



How about a dish antenna? Isn't the capture area proportional to the
physical area of the dish?


Indeed it is, in the front direction. But how about a dipole? The
capture area (or gain) broadside to an infinitesimal dipole is just
slightly less than that of a half wavelength dipole. And wire diameter
makes almost no difference.

Sorry, the theoretical construct is just a little too much like
Calvinball to hold my interest. I'll bow out now. Best luck in sorting
it out.

Roy Lewallen, W7EL

Antenna gain question
 

Roy Lewallen wrote:
Of course, any rays reaching the center would
continue on through, Cecil's unique theories notwithstanding.

The way the incoming fields were defined, they all converge
at a point in the center of the sphere. Presumably, that's
where the isotropic antenna is located. Replacing the isotropic
with a Yagi whose feedpoint is logically located at the point
of convergence means that any part of the field that doesn't
encounter parts of the Yagi before the point of convergence will
converge at the feedpoint on the driven element of the Yagi in
a defaulting isotropic manner. Given the definition of the
spherical fields, there is no part of the fields that will not
encounter the Yagi.

Therefore, the isotropic and the Yagi receive the same amount of
energy, i.e. all that exists in the spherical fields. Any energy
not received by the Yagi beam elements is received in a default-
isotropic mode at the Yagi feedpoint.
--
73, Cecil http://www.qsl.net/w5dxp

Antenna gain question
 

Cecil Moore wrote:

Jim Kelley wrote:

And still, rotating the antenna has nothing to do with summing the
signals - coherently, or otherwise. Agreed?


Are we talking normal operation or receiving big
bang background radiation?

The source of radiation was not described; only its distribution. It
was like being surrounded isotropically by radio sources - not unlike
the 3 K background. But there are other sources which pretty well
surround us as well.

ac6xg

Antenna gain question
 

But what if it was rented from Avis?

"Richard Clark" wrote in message specific, then yes
the car will radiate by the same principle at
5 zetta-yottaHertz

73's
Richard Clark, KB7QHC

Antenna gain question
 

For your conceptual purposes, your question would be similar to this?:

In a deep focal point of parabolic dish two antenns are mounted...

Which of them it does pick up more energy?

An antenna with 180 degree beamwidht or an highly directional antenna
with 0,1 degree beamwidth (both pointed to dish, of course)?

(In focal point of dish there are convergent frontwaves also). (We
could think in a sperical dish, also).

73's

Miguel Ghezzi (LU 6ETJ)

Antenna gain question
 

Jim Kelley wrote:

Cecil Moore wrote:
Are we talking normal operation or receiving big
bang background radiation?

The source of radiation was not described; only its distribution. It
was like being surrounded isotropically by radio sources - not unlike
the 3 K background. But there are other sources which pretty well
surround us as well.

OK, sometimes I lose the context. If the radiation is arriving
isotopically, it doesn't matter which direction the Yagi is
pointed (as I inferred from what you said).

But arriving isotropic radiation would all converge at a point.
If a plumber's delight Yagi driven element is centered on that
point, it would receive all the radiation in a default-isotropic
mode.
--
73, Cecil http://www.qsl.net/w5dxp

Antenna gain question
 

Ron, W4TQT wrote:
"How about a dish antenna?"

The parabolic reflector converts the spherical waves of its radiator at
the focus of the parabola into a plane wave of uniform phase across the
mouth or aperture of the parabola. Mouth ans aperture are syninymous
when applied to parabolic, lens, and horn antennas. Rays enter and exit
parallel but reflect through the focal point. Reciprocity rules and the
path through the antenna is the same, coming or going. The parabolic
reflector antenna sends and receives to and from a familiar spot on its
axis and at a distance. It is inoperative outside the spot and its path
of travel. The larger the parabola, the smaller the diameter of the
spot, and the higher the power gain.

The beamwidth of a large circular aperture such as a parabolic antenna
is inversely proportional to its diameter in wavelengths. The total
field radiated by a arabola is the vector sum of the fields generated by
the elementary areas making up the aperture or mouth of the parabola.
The directive gain of a parabola antenna is directly proportional to the
area of its mouth and inversely proportional to the wavelength squared.
See 1955 Terman page 899, equation (23-28) as pointed out at the bottom
of page 911.

Best regards, Richard Harrison, KB5WZI

Antenna gain question
 

Cecil Moore wrote:

Jim Kelley wrote:


Cecil Moore wrote:

Are we talking normal operation or receiving big
bang background radiation?


The source of radiation was not described; only its distribution. It
was like being surrounded isotropically by radio sources - not unlike
the 3 K background. But there are other sources which pretty well
surround us as well.


OK, sometimes I lose the context. If the radiation is arriving
isotopically, it doesn't matter which direction the Yagi is
pointed (as I inferred from what you said).

But arriving isotropic radiation would all converge at a point.
If a plumber's delight Yagi driven element is centered on that
point, it would receive all the radiation in a default-isotropic
mode.

I think Roy pretty well nailed the answer. An interesting result - both
antennas producing equal signals. I'd like to check that by comparing a
dipole to an isotropic in such a field. I assume the results would be
the same. Again, an interesting result. But you both bring some
interesting points.

ac6xg

Antenna gain question
 

Miguel Chezzi, LU6ETJ wrote:
"In a deep focal point of parabolic dish two antennas are mounted...

Which of them does pick up more energy?
An antenna with 180 degree beamwidth or a highly directional sntenna
with 0.1 degree beamwidth (both pointed to dish, of course)?"

I`ll risk being the fool. We sometimes test for illumination of a
reflector. We would not be concerned were it not advantageous to do so.

With 180-degree radiation, we fill the dish, using all its surface.
With 0.1-degree illumination, we might as well remove all but the
illuminated area. It would save dead load and wind loading.

My answer: The 180-degree radiation angle will receive a larger area of
the plane-wavefront and extract more watts from the wave with a given
number of watts per square area.

Best regards, Richard Harrison, KB5WZI

Antenna gain question
 

Richard Harrison wrote:

Miguel Chezzi, LU6ETJ wrote:
"In a deep focal point of parabolic dish two antennas are mounted...

Which of them does pick up more energy?
An antenna with 180 degree beamwidth or a highly directional sntenna
with 0.1 degree beamwidth (both pointed to dish, of course)?"

I`ll risk being the fool. We sometimes test for illumination of a
reflector. We would not be concerned were it not advantageous to do so.

With 180-degree radiation, we fill the dish, using all its surface.
With 0.1-degree illumination, we might as well remove all but the
illuminated area. It would save dead load and wind loading.

My answer: The 180-degree radiation angle will receive a larger area of
the plane-wavefront and extract more watts from the wave with a given
number of watts per square area.

Best regards, Richard Harrison, KB5WZI

The question you have to ask yourself is, does it intercept all of the
energy reflected toward it, or only some fraction of it.

We should always be cognizant of the limits imposed by the absence of a
free lunch.

ac6xg

Antenna gain question
 

Jim Kelley, AC6XG wrote:
"The question you have to ask yourself is, does it intercept all of the
energy reflected toward it, or only some fraction of it."

Nothing is perfect as Jim observes. "Imperfections" are sometimes
exploited to improve an antenna pattern. To a first approximation
though, we assume that all the parallel rays intercepted by a dish are
focused on the radiator and aid, adding in-phase. Received carrier power
excites the antenna and this causes a minimum of 50% of this power to be
re-radiated if the antenna is perfectly matched to to the receiver load.
The antenna`s radiation resistance in this case becomes the Thevenin`s
source resistance for the receiver load on the antenna. This requires a
conjugate match between the antenna and receiver input impedances.

50% of the received power to the receiver is the best that can be done
under optimum conditions, that is , with a perfect match. With a 100%
mismatch, a short-circuit, 100% of the intercepted power is re-radiated
by the antenna. If the antenna is open-circuited, it accepts none of the
power focused upon it.

Best regards, Richard Harrison, KB5WZI

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

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

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

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

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

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

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

Antenna gain question
 

Richard Clark wrote:

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

An antenna one, rather than an antenna +/- source one. Yes.

73, ac6xg

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

Antenna gain question
 

Very nice work. Dissapointingly ambiguous results.

Thank you.

ac6xg

Richard Clark wrote:

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

Antenna gain question
 

Richard,

It's not clear what aspect of your sources is "Rnd", but the fact that
they are monochromatic is still problematic.

73, ac6xg

Jim Kelley wrote:
Very nice work. Dissapointingly ambiguous results.

Thank you.

ac6xg

Richard Clark wrote:

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

Antenna gain question
 

On Fri, 04 Nov 2005 10:32:07 -0800, Jim Kelley
wrote:

It's not clear what aspect of your sources is "Rnd", but the fact that
they are monochromatic is still problematic.

Hi Jim,

You lost me on that curve. Monochromatic. The sources exhibit an
even distribution of varying phase in a random order. That was
tedious to accomplish, but achievable - in a group of 360 possible
degrees of phase, you eventually cover the field. On the other hand,
if you are suggesting that there needs to be an equally random
distribution of frequencies then that has its obvious issues of
practicability. What is the lowest frequency and what is the highest
frequency? That question has all the hallmarks of which infinity is
the biggest?

Anyway, I would surmise that if I could achieve both random phase and
frequency distribution, then the difference between a simple dipole's
response and that of a yagi antenna would be trivial. This would be a
given seeing that the parasitic elements would be virtually invisible,
rendering the "driven" element un-differentiable from the simple
dipole.

73's
Richard Clark, KB7QHC

Antenna gain question
 

Richard Clark wrote:


Anyway, I would surmise that if I could achieve both random phase and
frequency distribution, then the difference between a simple dipole's
response and that of a yagi antenna would be trivial.

Trivial would be a nice change.

This would be a
given seeing that the parasitic elements would be virtually invisible,
rendering the "driven" element un-differentiable from the simple
dipole.

i.e. what Roy said. But I think there's still more to it. I tried to
give the other Richard a hint about it but it didn't resonate.

73, ac6xg

Antenna gain question
 

Jim Kelley wrote:
i.e. what Roy said. But I think there's still more to it. I tried to
give the other Richard a hint about it but it didn't resonate.

Then obviously your XC didn't equal your XL.
--
73, Cecil http://www.qsl.net/w5dxp