"Dave Platt" wrote in message
...
In article tJLne.13595$Vm4.9195@trnddc01,
Dale Parfitt wrote:

How can a T match have show a bias- it is balanced. Virtually all the
serious EME arrays use this matching technique and show the major lobe
dead
off the front.

Are they feeding directly off of the coax, or do they use a halfwave
(or other) balun between the coax and the T?

Seems to me that a T directly from coax could show some amount of
imbalance. The center-conductor current would have only one pathway
to feed (the T), while the shield current would have two (the other
side of the T, and back down the feedline). If the outside of the
feedline was an integral number of halfwaves down to the point at
which it's grounded, there might be enough current flow on the outside
of the feedline to disturb the balance and change the pattern somewhat.

Sticking a half-wave coax balun at the input of the T ought to resolve
this pretty well, no?

yes, that is how most of them i have seen work. a 1/2 wave phasing line is
used to feed the 'opposite' side of the T making it properly balanced.

Dave:

I had mentioned 1/2 wave monopole above--right now I am in the "1/2 wave
vertical monopole period of life"... grin... freq 10 meter on up...

Warmest regards,
John
"Dave" wrote in message
...
but a vertical monopole about 1/4 wave long doesn't even need a
matching
system in most cases... unless you are a real perfectionist. just
what are
you trying to build here anyway?

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

Sorry, didn't mean that sort "balance"--as in a balanced antenna...
you
are right to make me be more specific...

...rather, I mean in the radiated rf field pattern of the antenna
itself--because the T-Match is only on one side of the driven
element--the radiation will not be completely circular (as in a
vertical)--and will begin formation of a stronger pattern in one
direction over all other directions on a compass, this is in
reference
to a vertical monopole, but still would be in effect in a horizontal
version, in affecting a stronger pattern in one direction.... (and
of
course, there is no such thing as a "perfect" pattern, just degrees
of
more or less.)

Warmest regards,
John

"Cecil Moore" wrote in message
...
John Smith wrote:
The T-Match will still show a favor in signal launch because of
the
imbalance of the gamma rods on one side, ...

A T-match is balanced because it is right+left gamma
matches, i.e. gamma rods on both sides with two equal
series caps (or tube caps).
--
73, Cecil, http://www.qsl.net/w5dxp

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"Dave Platt" wrote in message
...
In article tJLne.13595$Vm4.9195@trnddc01,
Dale Parfitt wrote:

How can a T match have show a bias- it is balanced. Virtually all the
serious EME arrays use this matching technique and show the major lobe
dead
off the front.

Are they feeding directly off of the coax, or do they use a halfwave
(or other) balun between the coax and the T?

Check out any of the antenna handbooks for a Tee match. The driven element
is insulated from the boom and split in the middle. Each side of the Tee
taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A 4:1
coaxial balun is used to transform the 200 Ohms balanced down to 50 Ohms
unbalanced.

Dale W4OP

Dale:

Yes, someone injected a T-Match in here, but no real interest in a
T-Match...

Warmest regards,
John

"Dale Parfitt" wrote in message
news:ODOne.7695$vK5.2782@trnddc03...

"Dave Platt" wrote in message
...
In article tJLne.13595$Vm4.9195@trnddc01,
Dale Parfitt wrote:

How can a T match have show a bias- it is balanced. Virtually all
the
serious EME arrays use this matching technique and show the major
lobe
dead
off the front.

Are they feeding directly off of the coax, or do they use a halfwave
(or other) balun between the coax and the T?

Check out any of the antenna handbooks for a Tee match. The driven
element
is insulated from the boom and split in the middle. Each side of the
Tee
taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A
4:1
coaxial balun is used to transform the 200 Ohms balanced down to 50
Ohms
unbalanced.

Dale W4OP

I should have pointed out, a T-Match requires a dipole, a few seem to
miss I had previously noted this is a monopole in question... a T-Match
would unbalance the RF RADIATION PATTERN of a dipole in the same way a
gamma does a monopole, there would be no gain from using a T-Match in
place of a gamma, EVEN if it could be done here...
I suppose you might be able to mount the bottom of T-Match on the mast
holding the monopole--but then, that is another experiment for another
day...

Warmest regards,
John
"John Smith" wrote in message
...
Dale:

Yes, someone injected a T-Match in here, but no real interest in a
T-Match...

Warmest regards,
John

"Dale Parfitt" wrote in message
news:ODOne.7695$vK5.2782@trnddc03...

"Dave Platt" wrote in message
...
In article tJLne.13595$Vm4.9195@trnddc01,
Dale Parfitt wrote:

How can a T match have show a bias- it is balanced. Virtually all
the
serious EME arrays use this matching technique and show the major
lobe
dead
off the front.

Are they feeding directly off of the coax, or do they use a halfwave
(or other) balun between the coax and the T?

Check out any of the antenna handbooks for a Tee match. The driven
element
is insulated from the boom and split in the middle. Each side of the
Tee
taps out on the D.E. at a point yielding a 200 Ohm balanced feed. A
4:1
coaxial balun is used to transform the 200 Ohms balanced down to 50
Ohms
unbalanced.

Dale W4OP

John Smith wrote:
I should have pointed out, a T-Match requires a dipole, a few seem to
miss I had previously noted this is a monopole in question...

Is there any difference in a 1/2WL monopole element and a
1/2WL dipole element sans the T-Match? I can't think of any.
--
73, Cecil http://www.qsl.net/w5dxp

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Not that I am aware of, only thing is there is no where to "hang" that
T-Match--well, the mast I mentioned... and the fact the monopole is
absent the bottom half of a dipole element... this is especially
notable if the bottom end of the monopole is sitting on the ground...
that tends to remove all confusion... grin

Warmest regards,
John
"Cecil Moore" wrote in message
...
John Smith wrote:
I should have pointed out, a T-Match requires a dipole, a few seem to
miss I had previously noted this is a monopole in question...

Is there any difference in a 1/2WL monopole element and a
1/2WL dipole element sans the T-Match? I can't think of any.
--
73, Cecil http://www.qsl.net/w5dxp

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.... err, not to be confused with a "dipole beam", which is better
referred to as a "two element beam" to remove all confusion... grin

Warmest regards,
John

"John Smith" wrote in message
...
Not that I am aware of, only thing is there is no where to "hang" that
T-Match--well, the mast I mentioned... and the fact the monopole is
absent the bottom half of a dipole element... this is especially
notable if the bottom end of the monopole is sitting on the ground...
that tends to remove all confusion... grin

Warmest regards,
John
"Cecil Moore" wrote in message
...
John Smith wrote:
I should have pointed out, a T-Match requires a dipole, a few seem
to miss I had previously noted this is a monopole in question...

Is there any difference in a 1/2WL monopole element and a
1/2WL dipole element sans the T-Match? I can't think of any.
--
73, Cecil http://www.qsl.net/w5dxp

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Dale Parfitt wrote:

"John Smith" wrote in message
...

Dave:

The T-Match will still show a favor in signal launch because of the
imbalance of the gamma rods on one side, on a beam this could even be
manipulated to ones favor--not as likely on a monopole... just looking
for a way to completely balance the field pattern...
I just thought someone had most likely done something like this
before... if I don't hear of anyone, will shove some various sized
drain, stove pipe, soldered cans, etc. over a 1/2 monopole in place of
the gamma rod and check it out this weekend...

Warmest regards,
John
How can a T match have show a bias- it is balanced. Virtually all the

serious EME arrays use this matching technique and show the major lobe dead
off the front.

Dale W4OP



Dale

Was that you I worked while mobile on 6 yesterday or the day before?
Sounds like the call I remember.

tom
K0TAR

in other words i think he is trying to make a J pole into a coaxial
arrangement where the short part of the J wraps all the way around the pole.
personally it sounds like a lot of work to get rid of some small assymetry
caused by the gamma rod. the easier solution is a plain vertical with a
tuner to make the transmitter happy.

"John Smith" wrote in message
...
... err, not to be confused with a "dipole beam", which is better
referred to as a "two element beam" to remove all confusion... grin

Warmest regards,
John

"John Smith" wrote in message
...
Not that I am aware of, only thing is there is no where to "hang" that
T-Match--well, the mast I mentioned... and the fact the monopole is
absent the bottom half of a dipole element... this is especially
notable if the bottom end of the monopole is sitting on the ground...
that tends to remove all confusion... grin

Warmest regards,
John
"Cecil Moore" wrote in message
...
John Smith wrote:
I should have pointed out, a T-Match requires a dipole, a few seem
to miss I had previously noted this is a monopole in question...

Is there any difference in a 1/2WL monopole element and a
1/2WL dipole element sans the T-Match? I can't think of any.
--
73, Cecil http://www.qsl.net/w5dxp

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