John, do not allow yourself be led astray by the waffle on this
newsgroup of the importance of supposed antenna gains and the
differences between one exaggerated radiation pattern and another.

Real professsional radio engineers (who are extremely few and far
between) who, to make an honest living, are obliged to work in the
real world, and are accustomed to dealing with radio-path propagation
uncertaintainties of plus or minus 10, 15 or even 20 dB.

But perhaps you already find enough amusement with such silly
back-to-front ratios as 50 dB and this little warning is unnecessary.
I'm sure it is.
----
Reg.

After so many waffling contributions to the newsgroup from you
'experts' - where is the Gamma-match design formula? There are only
2 or 3 dimensions involved. It should be simple and straightforward
enough!

Or is this newsgroup just a farce?
----
Reg.

On Mon, 4 Apr 2005 15:56:39 +0000 (UTC), "Reg Edwards"
wrote:
Or is this newsgroup just a farce?

Hi Reggie,

Surely at your age, and experience writing here, you MUST know the
answer to that by now.

73's
Richard Clark, KB7QHC

Reg:



Your point is well taken here. I was wondering if it was just me and, I
ended up throwing away valuable posts because I was unable to recognize
pertinent posts; some posts do leave me asking a question, "Why would some
authors even post replies which contain no useable facts, data, and
comments--what is their intent?"



In the end, I chalked it up to, perhaps, younger people entering the arena
of discussion in "the real world" and, perhaps it would take them a bit of
time to experience what works and what does not.



Whatever this phenomenon is, your comments have been reassuring to my not
being alone in observing this behavior, THANKS!



Warmest regards,

John


--
Hay, if'n ya'll cun't konstructivly partecipete in this har disscusion, haw
aboot speel-checkin it fer me?


"Reg Edwards" wrote in message
...
After so many waffling contributions to the newsgroup from you
'experts' - where is the Gamma-match design formula? There are only
2 or 3 dimensions involved. It should be simple and straightforward
enough!

Or is this newsgroup just a farce?
----
Reg.

On Sun, 3 Apr 2005 13:24:27 -0700, "John Smith"
wrote:

[snip]

The "Monopole" I had pictured in my mind was a 1/2 wave end-fed, but, I was
not sure if the gamma would even be suitable for this use--and I attempted
to leave my original question open-ended to catch this, if that was the
case.

I am glad you pointed out the center of a driven element, such as in a yagi,
is "dead" and can be attached directly to ground. If a 1/2 end-fed monopole
can be matched with gamma--would that still be the same case, only here the
"end" could be attached to a grounded mast?

The gamma is normally used to feed the center of the driven element of
a Yagi where the feedpoint impedance is lower than that of the
transmission line and it is desired to have an unbroken element.

Another application is to shunt feed a grounded monopole, such as when
a grounded tower is used as a radiator. In this case too, the base
impedance is lower than the transmission line Z.

Both cases use the gamma as an impedance "step-up" transformer.

Because you suggest an end-fed half-wave, where the impedance is much
greater than 50-70 Ohm, I see no compelling reason to opt for a gamma
feed, other than the case when you want to ground the end of the
radiator (which may be what you have in mind).

While it is convenient to think of the gamma as a system where a "50
Ohm point" is located on the radiator and a tap made to it, the
reality is that the system is *much* more complicated and involves
mutual coupling, transmission line effects, etc, between the gamma rod
and the radiator. A moments reflection (no pun intended) will make
this obvious. If a "50 Ohm point" is the only goal then the gamma rod
diameter and spacing would not be factors.

Additionally, there is a multiplicity of combinations that will
present a match, at one frequency. Each will have a different
effective bandwidth, however.

Suggested reading:

"A New Look at the Gamma Match", QEX, May/June 1999, pp 23-31

On Mon, 04 Apr 2005 10:10:44 -0700, Wes Stewart
wrote:

[snip]

Another application is to shunt feed a grounded monopole, such as when
a grounded tower is used as a radiator. In this case too, the base
impedance is lower than the transmission line Z.

Before I'm taken to task, let me add, "is usually lower" than the
transmission line Z.\

Shunt feeding can be/is done on towers longer than 1/4 wavelength
where the Z at the bottom of the tower is higher than Zo.

J:

College was and is a great institution.
However, the most valuable professors/instructors I ever had the pleasure to
study under seemed to share one common element--they had all first worked in
private enterprise before entering the academic professions (scouting rounds
a guy out!)
My first degree was in electronic engineering. When the focus of this
seemed to move off shore and other employment opportunities became available
(and the Apple, then the IBM PC, came to be), I returned to college and
focused my attention in the field of computer science.
Being an older student at that time and possessing a bit of "street-smarts",
I was able to side step issues which I had found NOT be in "vogue" of my
instructors beliefs.
Although these institutions are a great forum for debate and argument--I was
able to see little value in endangering my grades with such which would be
contrary to my instructors favorite pet ideas (indeed, while in their
classrooms, they all thought--I thought, they were the most handsome (or
beautiful--if female) and gifted instructor(s) I ever had the pleasure to
study under grin.)
Some instructors are quick to point out, "There are NO dumb questions, just
dumb people who don't ask questions."
However, although they may state the above--following their own advice
seemed to be a bit more of a challenge to many of them and, some were better
in the implementation of that ideal than others; somehow, it left me with
the opinion that a more accurate translation to this advice would have been,
"If you don't agree with me and the course material I have chosen for this
course--YOU WILL PAY!"
But, I make no mistake--I am humbly indebted to ALL instructors for their
time and efforts--I value all who lives I touched in those hallowed halls.
To this day, I do work with encryption/decryption methods and protocols.
Frequently I employ another questionable practice--security through
obscurity; this fills my dreams with seemingly psychic visions of past
instructors cringing in dark corners in loathing contempt and fear of such
arcane and cheap methods...

Rather frequently I utter (under my breath), "Whatever works!" guilty
smile

Warmest regards,
John

--
Hay, if'n ya'll cun't konstructivly partecipete in this har disscusion, haw
aboot speel-checkin it fer me?


"J. Mc Laughlin" wrote in message
...
Well "John Smith," wherever and whoever you are, you are receiving
valuable
advice from several quarters.
Our students are required to use top-down programming in computer
engineering and in computer science classes. If your professors did not
convince you of its importance, far be it for me to try.

Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:

Cecil:
I stand corrected...

Warm regards,
John

--
Hay, if'n ya'll cun't konstructivly partecipete in this har disscusion, haw
aboot speel-checkin it fer me?


"Cecil Moore" wrote in message
...
John Smith wrote:
Just for my curriosity, I will do a full-wave with a T-Match ...
(seems a 1 wave vertical is best suited for high angle radiation
pattern.)

An *end-fed* one wavelength vertical fed against ground has
a high angle radiation pattern, e.g. 36 deg TOA. A one wavelength
vertical with a T-Match is a center-fed antenna. Such an antenna
has a *low angle* radiation pattern, e.g. 11 deg TOA.
--
73, Cecil http://www.qsl.net/w5dxp

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----= East and West-Coast Server Farms - Total Privacy via Encryption
=----

Wes:
I believe you are correct--my use of the gamma is rather unconventional here
(how would one describe this antenna, "A J-Pole without 1/4 wave matching
section?", having been replaced with the gamma.)
However, my first impressions from my limitied observations is that there IS
an increase in received signal strength from the most distant stations, and
appearing as 1-2 S-units with the use of a gamma match (ok, maybe something
else is responsible--but I can't see it.)
The gamma I am using is constructed of all copper (3/8 tubing at the moment)
with soldered connections, other than the sliding clamp attaching it to the
end fed monopole (copper clamp to the copper element of the monopole)--it
replaces an L-Network of #8 copper wire using a capacitor of copper plates
and telflon dielectric material.
Unless there is another varible at work--the gamma side of the monopole
seems to have a bit more of the patterns favor--but barely noticeable
(spacing of the gamma rod from monopole is ~4 inches.)

Regards,
John
--
Hay, if'n ya'll cun't konstructivly partecipete in this har disscusion, haw
aboot speel-checkin it fer me?


"Wes Stewart" wrote in message
...
On Sun, 3 Apr 2005 13:24:27 -0700, "John Smith"
wrote:

[snip]

The "Monopole" I had pictured in my mind was a 1/2 wave end-fed, but, I
was
not sure if the gamma would even be suitable for this use--and I attempted
to leave my original question open-ended to catch this, if that was the
case.

I am glad you pointed out the center of a driven element, such as in a
yagi,
is "dead" and can be attached directly to ground. If a 1/2 end-fed
monopole
can be matched with gamma--would that still be the same case, only here
the
"end" could be attached to a grounded mast?

The gamma is normally used to feed the center of the driven element of
a Yagi where the feedpoint impedance is lower than that of the
transmission line and it is desired to have an unbroken element.

Another application is to shunt feed a grounded monopole, such as when
a grounded tower is used as a radiator. In this case too, the base
impedance is lower than the transmission line Z.

Both cases use the gamma as an impedance "step-up" transformer.

Because you suggest an end-fed half-wave, where the impedance is much
greater than 50-70 Ohm, I see no compelling reason to opt for a gamma
feed, other than the case when you want to ground the end of the
radiator (which may be what you have in mind).

While it is convenient to think of the gamma as a system where a "50
Ohm point" is located on the radiator and a tap made to it, the
reality is that the system is *much* more complicated and involves
mutual coupling, transmission line effects, etc, between the gamma rod
and the radiator. A moments reflection (no pun intended) will make
this obvious. If a "50 Ohm point" is the only goal then the gamma rod
diameter and spacing would not be factors.

Additionally, there is a multiplicity of combinations that will
present a match, at one frequency. Each will have a different
effective bandwidth, however.

Suggested reading:

"A New Look at the Gamma Match", QEX, May/June 1999, pp 23-31

John Smith wrote:
Reg:



Your point is well taken here. I was wondering if it was just me and, I
ended up throwing away valuable posts because I was unable to recognize
pertinent posts; some posts do leave me asking a question, "Why would some
authors even post replies which contain no useable facts, data, and
comments--what is their intent?"



In the end, I chalked it up to, perhaps, younger people entering the arena
of discussion in "the real world" and, perhaps it would take them a bit of
time to experience what works and what does not.



Whatever this phenomenon is, your comments have been reassuring to my not
being alone in observing this behavior, THANKS!



Warmest regards,

John


(Sigh!)

I put all the gamma match info I have on a.b.s.e (I think; it hasn't
appeared there yet)under subject "Gamma match article and executable." One
is an article in PDF format and the other is a DOS executable for designing.
Use whichever one floats your boat.

John - KD5YI