"Sal M. Onella" wrote in
:


"Cecil Moore" wrote in message
...
Sal M. Onella wrote:
I'm starting to think in terms of Smith charts, which I never
thought I would need or use. Surprise!

Carrying a Smith Chart around in your head is a
good way to conceptualize transmission line and
antenna configurations.
--
73, Cecil http://www.w5dxp.com

Yes. I have seen a lot of Smith charts for broadband Navy shipboard
antennas. The people who match them obviously have to do a chart for
the raw antenna in place on the ship, then design and adjust a
matching network, followed by a chart of the results, with every point
inside the 3:1 (or 4:1) circle. Their efforts are generally
documented in the ships' antenna files.

I agree about the Smith chart for conceptualizing but at this stage, I
am just a Smith baby.

Back on topic, I am using the sleeve in a conventional dipole
configuration until I can take the time to apply the ideas presented
in this NG. I noticed this afternoon that coiling four turns of
decoupling loop a few feet from the feed actually raised the VSWR,
which I didn't understand. Also, where the coax hangs down next to
the antenna makes a difference in the VSWR, so obviously the line is
not "flat" and is instead part of the antenna. (Do we still use the
term "flat" to describe a transmission line which is properly matched
to the load? I recall it from Navy training more than 40 years ago.)

Yes, I think that the meaning taken for a "flat line" is one with 1:1 or
close VSWR, flat to mean the magnitude of the voltage (or current) is
approximately constant all all positions on the line, and that describes
only what is happening on the inside of the line. That doesn't preclude
current flowing on the outside of the line which seems to be your issue.
I won't confuse you with examples of where the outside of the line is
intended to carry current and at the same time the VSWR is low, but it is
possible and sometimes desired.

I agree with you that if you change the feedline routing physically, and
you see a consequent change in VSWR, that suggests the outside of the
feedline carries current and is part of the radiating system, and I don't
think that is what you want.

My first HF antenna works, but it's clearly no marvel.

Look upon it as an opportunity for learning. After all, what would you do
if it just worked?

Owen