Reg Edwards wrote:

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!

Reg, is this the question? Where is the ratio of the real
part of the net voltage to the real part of the net current
equal to 50 ohms? Or is it more complicated than that?
--
73, Cecil http://www.qsl.net/w5dxp


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John Smith wrote:
"Why would some authors even post replies which contain
no useable facts, data, and comments--what is their intent?"

My Mother had a take on such folk: They're just talking
to hear their heads rattle.
--
73, Cecil http://www.qsl.net/w5dxp


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John Smith wrote:
Cecil: I stand corrected...

John, more like "I stand expanded." I wasn't correcting you.
I was just expanding upon your statement. You were entirely
correct about a one wavelength vertical end-fed against ground.
--
73, Cecil http://www.qsl.net/w5dxp


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Just to take a side avenue to this all, I dropped down another 1/2 wave
element adjacent to 1/2 monopole under discussion, with a shorting strap the
top of the elements (converting the 1/2 monopole into an upside down
"U"--or, resembling a slim-jim with 1/4 wave match replaced by the gamma),
guess what? Yes, a noticible improvement....

Regards,
John

--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"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.

Glen:

THAT is a very interesting URL, thank you for the time in bringing it to my
attention; it is apparent that my internet searchs are missing important
documents!

Dr. Montoya is "my kinda guy."

Regards,
John

--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"Glen Overby" wrote in message
...
John Smith wrote:
Anyone work with the gamma-match to the point of becomming a guru?
I am looking for "Everything you wanted to know about a gamma-match--in a
nutshell."

Start with the ARRL Antenna Book. My 19th Edition, (C) 2000, discusses
gamma
matches in chapter 26: Coupling the Line to the Antenna.

In other words, what set of formulas would give you length, conductor
spacing, gamma capacitor value, ratio of gamma rod to driven element
diameter, and a starting measurement for the shorting bar between
conductors-- for a given frequency?

The best resource I've found for this is lecture notes by Dr. Thomas
Montoya
at:

http://montoya.sdsmt.edu/ee492/fall2...2_fall2004.htm

Glen, kc0iyt

John Smith wrote:
"In other words, what set of formulas would give you length, conductor
spacing, hgamma capacitor value---?"

Arnold W.P. King was author of the Antennas section of "Transmission
Lines, Antennas, and Wave Guides", McGraw-Hill, 1945. Wing wrote
"Transmission Lines". Mimno wrote "Wave Guides".

On page 158, King wrote:
"---it is possible to modify the antenna itself in such a way that the
input impedance at its terminals is equal to the characteristic
impedance of the line. The usual arrangement, Hig. 28.3, is to attach
conductors at points CD along the antenna (which are not sufficiently
close to the near zone) and join these to the input terminals at AB. The
accurate calculation of the input impedance at AB of the modified
antenna as a function of the resistance CD and the lengths AC and BD has
not been accomplished."

I wouldn`t hold my breath waiting for accurate formulas, but you are
free to try it yourself. The gamma match is similar to the delta match
and must cope with some of the same problems. This may be a case for
experimentation.

Best regards, Richard Harrison, KB5WZI

O.K. Reg
I'll take you up on the 50 db F/B.
There are old wives tales and then there are old wives
who just tell tales about other old wives.Which is it?
I have never read anything definitive about max F/B figures attainable.
I have heard unsubstantiated stories about narrow voids filling up between
lobes
but no data to back it up so I would call that an old wives tale.
There are computor programs that show large F/B figures, shall we throw
those away together with your programs as computor programs are all suspect?
Actually I have not seen any measured data regarding F/B radiation with
respect to
lobe angles possibly because of difficulties with respect to measuring And
also
what height the antenna must be before lobe shapes stablises.?
Now you have come forward and stated, presumably by experience,
mathematics or what ever, that 50 db F/B is silly. Why so?
What F/B figure is not silly and why, plus what are the parameters
involved that make this F/B not silly? Does this F/B relate to all antennas,
yagi's, dish forms, verticals, wire arrangements or what?
I am so pleased somebody has all this data so as to really substantiate,
without doubt, that it really IS an old wives tale ,or is it somebody just
exercising
their right to free speech regardless of content.
I await your reply with interest, and ofcourse, the scientific data that
substantiate
what IS an old wives tale and what IS not, and........ without "waffle"
Regards
Art Unwin...KB9MZ....XG



"Reg Edwards" wrote in message
...
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.

snip

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.

To all:

Well, conductor diameter is not very critical in this configuration (or, at
least that appears true to me--strange as that is to swallow.) However, the
gamma rod I now have is #8 copper wire. And, that works out well, although
it needs a couple of extra insulating spacers to stabilize it to the
monopole, it is easy to work with and one only needs to solder it to the
copper monopole, it can be bent and straightened at will to adjust
spacings-shortened and lengthened by soldering on a bit.
Richard reminding me of the necessity of ferrite beads has made the tuning
of gamma much smoother, and an swr of 1.4:1 is now had--coax length changes
are MUCH less noticeable--bordering on trivial.
As it stands now, it is 32 ft. to the bottom of the monopole. The very
bottom of the monopole is connected to the aluminum mast, the mast is well
grounded (static and lighting protection are a given.) The monopole is now
in the configuration of a 1 wave folded monopole (end fed through a gamma.)
Placing the gamma in the middle of the two vertical lengths of the monopole
(at the bottom end of the open "U") seems to give a complete 360 degree EVEN
pattern, no noticeable bumps (perhaps a very slight elongation of the lobes
in the same plane as the two ends of the folded monopole.)
From my simple observations, I put the most weight in s-unit readings of
known signals I RECEIVE with a known transceiver and coax (this I consider
to be the most "real world" test I can devise.)
This configuration is, by far, the best I have had sitting on that mast. It
blows away the 1/4 wave I constructed (I am too worn out to put back the 1/4
and note the exact differences, but a safe estimate is 4+ s-units on all
known received signals here on the valley floor. This has to be a low
pattern, but critique and comments are welcomed to contest this.)
It might be my imagination, but there seems a very "solid" sound and feel to
signals (this is impossible to measure and will make many--if not all--doubt
my sanity!)
As some have noted, the humble s-unit will vary widely on transceivers, and
is fallible...
However, now I have an antenna of a, somewhat, seemingly unique
configuration which will give me a good conversation piece to chew over with
friends....
I am pressing this antenna into everyday use while I throw another together
to toy with the gamma on.

One more thing. I have found a beacon on 27.125 (Chicken Band Channel 14.)
It is on the air 24/7. It is a 20 MW child's walkie-talkie with a 9 ft.
antenna. It repeats the letters (call) "AOH" repeatedly at 7 wpm. I have
had email correspondence with the operator ", the above
details gleaned through such.
He/she claims it has been heard throughout northern and central California,
and that it is located high atop Mt. Diablo here in California.
It has been an asset in testing the antenna(s) in receive conditions, under
varying conditions, in "the real world."

Summary and conclusions:
-The gamma can be used to match a 1/2 wave end fed monopole with acceptable
results.
-The gamma can be used to match a 1 wave end fed folded monopole with
acceptable results.
-The 1 wave folded monopole seems a superior element to use in this design.
-Although only suspicion at this point, I suspect the gamma to be of
slightly less "lossy" performance than the L-Match previously used and/or
provides a more favorable "launch" to the radiation pattern desired--more
attention needs to be given this in future experiments. The experiments
continue.

Thanks all for your past and continuing assistance and council...

Regards,
John
--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"John Smith" wrote in message
...
Just to take a side avenue to this all, I dropped down another 1/2 wave
element adjacent to 1/2 monopole under discussion, with a shorting strap
the
top of the elements (converting the 1/2 monopole into an upside down
"U"--or, resembling a slim-jim with 1/4 wave match replaced by the gamma),
guess what? Yes, a noticible improvement....

Regards,
John

--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"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.

Art, KB9MZ wrote:
"O.K. Reg, I`ll take you up on the 50 dB F/B."

It requires good balance for such cancellation.

Kraus gives the gain for a 100-meter dish near Bonn, Germany on page 676
of the 3rd edition of "Antennas". Gain is a function of frequency and
varies from about 48 dB at 300 MHz to about 98 dB at 150 GHz. I don`t
know if shielding has been added to make this a "high-performance" dish
but I would wager that this enormous radio ear and mouth has an
excellent front-to-back ratio. Probably exceeds forward gain at some
azimuths and elevation angles.

Arnold B. Bailey has a lot to say anout a "connected" (driven) element
and a parasitic reflector, starting about on 447 of "TV and Other
Receiving Antennas", Bailey says:
"The optimum spacing for highest gain of a parasitic reflector is S=0.15
wavelength plus or minus 0.025. Here the relleector is operated at Q=+1
(longer than resonant) and the gain in direction 1 is approximately 5.5
dB. Reasonable compromise for a less critical system is to use a spacing
of 0.2 wavelength and a parasitic element longer than resonant (at
Q=+1). This case gives a gain in direction 1 of 5 dB."

On page 440 Bailey says: The front-to-back ratio ---is 17.5 dB in this
case, and the Y/X ratio only about 9 dB, where +X represents the optimum
direction.---" A picture is worth 1000 words.

Best regards, Richard Harrison, KB5WZI