John Smith wrote:
Your work with EZNEC is greatly appreciated here.
Your configuration is for a horz ant and I am working with a
vertical--conversion is trivial.
"A picture is worth a thousand words..." has real significance here.
I am sure an analysis of your file will provide me with insight into the
workings of EZNEC and accelerate my learning curve!

I knew I was confused about what you were trying to do.
If you just tilt the horizontal dipole to a vertical
position, it will still be center-fed. Are you trying
to gamma-match a 1/2WL vertical base-fed against a
radial system? If so, try this EZNEC file:
--
73, Cecil http://www.qsl.net/w5dxp/GAM20VHW.EZ

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Cecil Moore wrote:
I knew I was confused about what you were trying to do.

John, I just realized what is wrong with gamma feeding a
1/2WL vertical at the base. The currents in each side of
the gamma feed section are pretty much out-of-phase so
they don't radiate (much). Conclusion: Gamma feeding a
1/2WL antenna at the base results in a field strength
comparable to a 1/4WL vertical and the minuscule amount
of gain is not worth the effort. Antenna gurus probably
already knew that but it just dawned on my concrete brain.

In much the same way a Zepp or a J-Pole is not a 3/4WL
radiator even though they are 3/4WL long, a gamma match
on a base-fed 1/2WL vertical doesn't yield a 1/2WL
electrical radiator. For this reason, the length of a
gamma match should be considerably less than a wavelength.
A good rule of thumb is probably in the ballpark of less
than ~6% of a wavelength. Your idea seems to require about
16% of a wavelength.

Moral: Physical length and RF electrical length are not
always the same.

What you are trying to do apparently requires a J-Pole
or Zepp approach, i.e. a physical 3/4WL antenna.
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Cecil:
Yes Cecil, there is wisdom in your words...
However, as I pointed out, I am now focusing on "received signal", its'
quality and strength.
After having given it some thought, that is what is most important. In an
grave emergency I have the ability to bring multiple kilowatts on line (yes,
I have the generator to support it.) What I can't do is guarantee that for
the fellow at the other end of the contact. So, I am focusing my attention
towards his/her benefit--in the refinement of my ability to pull
sub-nano-watts from the ether...
EZNEC and all other calculations are great, I appreciate what can get me to
ballpark figures with matching, lengths, spacings, predictions, etc.
But, in the end, the humble s-meter on a known transceiver, compared against
know signals and similar conditions will be my final guide and the
determining factor.
To all which point out I "may only be"/am duplicating past work, while
making futile attempts, or expelling great amounts of energy in this
pursuit, I say: "It keeps me out of the bars and away from the wild women!"
(saves on my Jim Beam/Viagra bill too!)

Warmest 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!!!
"Cecil Moore" wrote in message
...
Cecil Moore wrote:
I knew I was confused about what you were trying to do.

John, I just realized what is wrong with gamma feeding a
1/2WL vertical at the base. The currents in each side of
the gamma feed section are pretty much out-of-phase so
they don't radiate (much). Conclusion: Gamma feeding a
1/2WL antenna at the base results in a field strength
comparable to a 1/4WL vertical and the minuscule amount
of gain is not worth the effort. Antenna gurus probably
already knew that but it just dawned on my concrete brain.

In much the same way a Zepp or a J-Pole is not a 3/4WL
radiator even though they are 3/4WL long, a gamma match
on a base-fed 1/2WL vertical doesn't yield a 1/2WL
electrical radiator. For this reason, the length of a
gamma match should be considerably less than a wavelength.
A good rule of thumb is probably in the ballpark of less
than ~6% of a wavelength. Your idea seems to require about
16% of a wavelength.

Moral: Physical length and RF electrical length are not
always the same.

What you are trying to do apparently requires a J-Pole
or Zepp approach, i.e. a physical 3/4WL antenna.
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
=----

John Smith wrote:

Cecil:
Yes Cecil, there is wisdom in your words...
However, as I pointed out, I am now focusing on "received signal", its'
quality and strength.
After having given it some thought, that is what is most important. In an
grave emergency I have the ability to bring multiple kilowatts on line (yes,
I have the generator to support it.) What I can't do is guarantee that for
the fellow at the other end of the contact. So, I am focusing my attention
towards his/her benefit--in the refinement of my ability to pull
sub-nano-watts from the ether...
EZNEC and all other calculations are great, I appreciate what can get me to
ballpark figures with matching, lengths, spacings, predictions, etc.
But, in the end, the humble s-meter on a known transceiver, compared against
know signals and similar conditions will be my final guide and the
determining factor.

I think you'll eventually end up finding out you just need a big tower
and a big beam.

ac6xg

have you tried this???
http://www.google.com/search?hl=en&q...ch+yagi+design
lots of sources for design info, some software, plenty of pointers.
basically once you have a yagi and decide to feed it with a gamma match you
have the following variables you can work with (assuming you aren't going
to change the diameter of the driven element)...
1. rod diameter
2. rod to driven element spacing
3. location of shorting strap
4. value of capacitance
5. length of driven element(don't forget this, it is very important part of
adjustment!)

now basically you pick a rod diameter, usually 1/3 to 1/2 the diameter of
the driven element, but basically whatever you happen to have handy that is
a reasonable length. then make a few brackets to space it a couple inches
from the driven element, from about 1" on 2m to maybe 4-5" on 20m. so that
fixes 1 and 2.. then you have 3 other variables you can adjust to get the
match you want. if you can't find a good match after systematically running
through the other 3 then try changing the spacing a bit and start again...
but i've always been able to get a decent match by just picking what was
handy for tubing and spacers.

and don't overlook a T match. if you use a 1/2 wave phasing line and the
right diameters and spacing you can get away without a capacitor. this
makes for a fully dc grounded plumbers delight construction that is very
rugged and simple to adjust. this was how all the old telrex monobanders
were fed.



"Jim Kelley" wrote in message
...


John Smith wrote:

Cecil:
Yes Cecil, there is wisdom in your words...
However, as I pointed out, I am now focusing on "received signal", its'
quality and strength.
After having given it some thought, that is what is most important. In
an
grave emergency I have the ability to bring multiple kilowatts on line
(yes,
I have the generator to support it.) What I can't do is guarantee that
for
the fellow at the other end of the contact. So, I am focusing my
attention
towards his/her benefit--in the refinement of my ability to pull
sub-nano-watts from the ether...
EZNEC and all other calculations are great, I appreciate what can get me
to
ballpark figures with matching, lengths, spacings, predictions, etc.
But, in the end, the humble s-meter on a known transceiver, compared
against
know signals and similar conditions will be my final guide and the
determining factor.

I think you'll eventually end up finding out you just need a big tower
and a big beam.

ac6xg

Hmmmm, your analysis is interesting. The gamma looks very much like an
"auto-transformer" to me--the gama-rod like a variable primary, the
secondary being the complete driven element.
I suspected the action would be identical to the auto-transformer--where ALL
the turns in the secondary deliver power to the load....

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!!!
"Cecil Moore" wrote in message
...
Cecil Moore wrote:
I knew I was confused about what you were trying to do.

John, I just realized what is wrong with gamma feeding a
1/2WL vertical at the base. The currents in each side of
the gamma feed section are pretty much out-of-phase so
they don't radiate (much). Conclusion: Gamma feeding a
1/2WL antenna at the base results in a field strength
comparable to a 1/4WL vertical and the minuscule amount
of gain is not worth the effort. Antenna gurus probably
already knew that but it just dawned on my concrete brain.

In much the same way a Zepp or a J-Pole is not a 3/4WL
radiator even though they are 3/4WL long, a gamma match
on a base-fed 1/2WL vertical doesn't yield a 1/2WL
electrical radiator. For this reason, the length of a
gamma match should be considerably less than a wavelength.
A good rule of thumb is probably in the ballpark of less
than ~6% of a wavelength. Your idea seems to require about
16% of a wavelength.

Moral: Physical length and RF electrical length are not
always the same.

What you are trying to do apparently requires a J-Pole
or Zepp approach, i.e. a physical 3/4WL antenna.
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
=----