"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 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 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

"Tom Ring" wrote in message
.. .
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

Hi Tom,
I knew the band was open because of 88-108 stations booming in, but my rotor
and remote antenna switch wires to the tower are temporarily disconnected
while we build a 180 ton rock wall behind the house. I'll be back on this
weekend.

Dale W4OP