When modelling close spaced element antenma
assemblies it is possible that some elements are
physically longer than the "driven" element.
Is the length of a element sufficient enough to
declare that element a " reflector" or are there
other caveates involved.( i.e. phase)
As background to this question I would point
out that that it is possible to have two closed
spaced (positioned) elements one of which is
shorter and one of which is longer than
the "driven " element, this combination being
placed either forward or to the rear of the
"driven " element.
Regards
Art

the length itself relative to the driven element length is not sufficient to
apply any particular label to an element of a parasitic antenna. it should
be noted that the terms 'director' and 'reflector' are not necessarily
scientific terms, they are more of a vague word description of how an
element apparently works based on the observation of the antenna pattern.
the real effect of each element of an antenna must be described by
describing the current magnitudes and phases and the physical location of
each element. a good example of this is a 2 element parasitic array, at one
frequency the parasitic element may be a 'director' and at another
frequency it could be described as a 'reflector'... without changing the
length of either the driven or parasitic element.

" wrote in message
news:u85ge.72716$c24.9252@attbi_s72...
When modelling close spaced element antenma
assemblies it is possible that some elements are
physically longer than the "driven" element.
Is the length of a element sufficient enough to
declare that element a " reflector" or are there
other caveates involved.( i.e. phase)
As background to this question I would point
out that that it is possible to have two closed
spaced (positioned) elements one of which is
shorter and one of which is longer than
the "driven " element, this combination being
placed either forward or to the rear of the
"driven " element.
Regards
Art

Dave
I was hoping that the IEEE would have a definition upon
which I could hang my hat on. Hate to see another quabble
like we had with TOA!
In my particular case I have two elements coupled in such
a way that even tho only one is driven the other is also of
the same phase ie. additive, all other elements are longer
than the driven element which suggests multiple reflectors,
absent an accepted definition.
Regards
Art

" wrote in message
news:u85ge.72716$c24.9252@attbi_s72...
When modelling close spaced element antenma
assemblies it is possible that some elements are
physically longer than the "driven" element.
Is the length of a element sufficient enough to
declare that element a " reflector" or are there
other caveates involved.( i.e. phase)
As background to this question I would point
out that that it is possible to have two closed
spaced (positioned) elements one of which is
shorter and one of which is longer than
the "driven " element, this combination being
placed either forward or to the rear of the
"driven " element.
Regards
Art

Art Unwin wrote:
"When modeling close spaced element antenna assemblies it is possible
that some elements are physically longer than the "driven" element. Is
the length of an element sufficient to declare a "reflector" or are
there other caveats involved (i.e. phase)?"

Art answered his own question. The element doesn`t care how it gets a
leading (capacitive) current, or a lagging (inductive) current.

In our broadcast curtain antenna arrays, we used an RCA WM-30A phase
monitor for the current angle in the ibnductive parasitic reflectors.
Phase was adjusted to spec with a short-circuit stub connected to where
the feedpoint would be if it were a driven element.

Kraus is unequivocal on page 245 of edition no. 3 of "Antennas":
"When the halfwave parasitic element is inductive (longer than its
resonant length) it acts as a reflector. When it is capacitive (shorter
than its resonant length) it acts as a director."

Best regards, Richard Harrison, KB5WZI

Interesting.
One respondent says position is a factor and the
other says it is not according to Kraus ,who may
well have been directing his comments at a Yagi
model So I changed the feed point on my model,
which is not a Yagi, to other elements to see if
they lagging or leading.
Surprise !
Some of the other elements were resonant also
thus they could be fed in one or more places
at the same time
Since with the initial design they are not all
directly fed these apparently do not fall into any
catagory.
I suppose literature in general can only apply
definitions to that which is known by the author
at the particular time
Regards
Art


"Richard Harrison" wrote in message
...
Art Unwin wrote:
"When modeling close spaced element antenna assemblies it is possible
that some elements are physically longer than the "driven" element. Is
the length of an element sufficient to declare a "reflector" or are
there other caveats involved (i.e. phase)?"

Art answered his own question. The element doesn`t care how it gets a
leading (capacitive) current, or a lagging (inductive) current.

In our broadcast curtain antenna arrays, we used an RCA WM-30A phase
monitor for the current angle in the ibnductive parasitic reflectors.
Phase was adjusted to spec with a short-circuit stub connected to where
the feedpoint would be if it were a driven element.

Kraus is unequivocal on page 245 of edition no. 3 of "Antennas":
"When the halfwave parasitic element is inductive (longer than its
resonant length) it acts as a reflector. When it is capacitive (shorter
than its resonant length) it acts as a director."

Best regards, Richard Harrison, KB5WZI

Well, everything stated may be true... but I have never seen a beam where
you would confuse the reflectors from the directors by physical size... if
in doubt and you wish to confirm this--just look up!

Warmest regards,
John
--
Sit down the six-pack!!! STEP AWAY!!! ...and go do something...
" wrote in message
news:u85ge.72716$c24.9252@attbi_s72...
| When modelling close spaced element antenma
| assemblies it is possible that some elements are
| physically longer than the "driven" element.
| Is the length of a element sufficient enough to
| declare that element a " reflector" or are there
| other caveates involved.( i.e. phase)
| As background to this question I would point
| out that that it is possible to have two closed
| spaced (positioned) elements one of which is
| shorter and one of which is longer than
| the "driven " element, this combination being
| placed either forward or to the rear of the
| "driven " element.
| Regards
| Art
|
|

John Smith wrote:

Well, everything stated may be true... but I have never seen a beam where
you would confuse the reflectors from the directors by physical size... if
in doubt and you wish to confirm this--just look up! Warmest regards, John

Given a beam with two identical driven elements, which is the
reflector and which is the director? :-)
--
73, Cecil http://www.qsl.net/w5dxp

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Well Cecil:

You know me and my fondness for "tweaking" electrical lengths grin... I
suspect it is more than possible to have 'em the same length, and indeed,
you seen the folded 1 wave monopole I played with, it did exhibit side
"nulls."

Now, as to if the gain of the beam you point out is exactly equal or better,
I doubt--as opposed to one being longer/shorter director/reflector
(remember, I still ponder the ethers part in all of this--and NONE of our
formulas take it into account)... but besides all of this...

I JUST HAVEN'T SEEN ONE!!!!

And, you know I am a hopeless "Assumer"--I dare to assume if it were such a
great idea, I'd see a bunch---but then, I am open to a discovery here!!!

Come on Cecil, with so many after my scalp--I can't afford losing any hair
to you!!! grin

I gotta get some work done here--I am turning off message notification... I
will read/respond to your come-back later... grin

Warmest regards,
John
--
Sit down the six-pack!!! STEP AWAY!!! ...and go do something...

"Cecil Moore" wrote in message
...
| John Smith wrote:
|
| Well, everything stated may be true... but I have never seen a beam
where
| you would confuse the reflectors from the directors by physical size...
if
| in doubt and you wish to confirm this--just look up! Warmest regards,
John
|
| Given a beam with two identical driven elements, which is the
| reflector and which is the director? :-)
| --
| 73, Cecil http://www.qsl.net/w5dxp
|
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Seems to me Cecil that the terms "Reflector" and
"Director" are very poor words to describe antenna
elements for an HF array .
I have oft times changed a single element into two
closely coupled elements and where one is short
and one is long relative to a driven element
I wonder who was the first to assign these terms
Or was it a poor translation from Japanese ( Uda and Yagi) ?
Regards
Art


Cecil Moore" wrote in message
...
John Smith wrote:

Well, everything stated may be true... but I have never seen a beam where
you would confuse the reflectors from the directors by physical size...
if in doubt and you wish to confirm this--just look up! Warmest regards,
John

Given a beam with two identical driven elements, which is the
reflector and which is the director? :-)
--
73, Cecil http://www.qsl.net/w5dxp

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News==----
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Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
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"John Smith" bravely wrote to "All" (11 May 05 09:21:00)
--- on the heady topic of " Reflector Vs Director"


It's all about the frequency, physical length, and spacing...


JS Reply-To: "John Smith"
JS Xref: aeinews rec.radio.amateur.antenna:30111

JS Well, everything stated may be true... but I have never seen a beam
JS where you would confuse the reflectors from the directors by physical
JS size... if in doubt and you wish to confirm this--just look up!

JS Warmest regards,
JS John
JS --
JS Sit down the six-pack!!! STEP AWAY!!! ...and go do something...
JS " wrote in
JS message news:u85ge.72716$c24.9252@attbi_s72...
JS | When modelling close spaced element antenma
JS | assemblies it is possible that some elements are
JS | physically longer than the "driven" element.
JS | Is the length of a element sufficient enough to
JS | declare that element a " reflector" or are there
JS | other caveates involved.( i.e. phase)
JS | As background to this question I would point
JS | out that that it is possible to have two closed
JS | spaced (positioned) elements one of which is
JS | shorter and one of which is longer than
JS | the "driven " element, this combination being
JS | placed either forward or to the rear of the
JS | "driven " element.
JS | Regards
JS | Art

.... There's always free cheese in a mousetrap.