On Tue, 19 Jun 2007 16:45:15 -0400, Chuck
wrote:

Hello Richard,

The complaints made here are far from sparse.

I've seen no complaints here at all
about matching difficulties. Even
posters who had used the antenna omitted
matching difficulties from their
reported experiences.

As I said, those that don't notice, don't complain. This is the human
condition. If they didn't notice, it must have matched (or they
didn't measure it, which is the same thing as not noticing).

We've seen plenty of complaints. Certainly they didn't lead with
their chin, the symptoms bore out the problem and they were
complaining of something they thought was remote from tuning; but not
far remote - meaning they "thought" it was tuned, but their rig was
going whacko.

On the other hand,
those who don't notice, don't complain. I will bet you have one
outlet in your home with inverted neutral/hot and a floating ground.
Does it bother how your lamp works?

I understand. But I really hoped to talk
about matching difficulties and find
myself awash in discussions of potential
common mode currents, about which I have
no truck. ;-)

You simply have to recognized the symptoms. If there are no symptoms,
there are no complaints. However, that doesn't mean their systems are
free of common modalities. It simply means the currents/voltages are
below the threshhold of notice.

Common Mode currents/voltages exist in EVERY system. It is merely the
degree and tolerance that become the issue.

Some folks have common mode complaints, others don't.

Sure. And I'd extend that to real,
center-fed dipoles with less than
perfect transmission line/antenna
symmetry. All a matter of degree?

Yup, as I anticipated in my earlier comment.

In that
vein, you stand to come out ahead if you seriously examine your
shack's quality of ground for all applications.

I'd do it immediately if it would help
explain the alleged matching
difficulties. ;-)

One solution for common mode problems is a ground tuner. This is also
called a virtual ground if the wire terminates in an open instead of
going to ground. What this does is references your rig/bench/room to
RF neutral. In that condition you don't notice that slight tingle
from the chassis as you brush the back of your fingers over it; or the
sizzle from the mike when your lips touch it. If your shack is
relatively close to the service ground, and the wire from your
rig/bench/ground runs only several feet; then everything should be
hunky dory. That is: up to a point where that length becomes a
significant fraction of the wavelength with a sizeable energy content.

At that point, you want to reduce the reactance of that wire by making
it one big Honker! Or, for a bench, you use a conductive sheet and
tack your equipment to the sheet. Usually a star (branching) system
of grounds is the best, but our equipment rarely exists in isolation
and there are cross connects. This can lead to ground loops (common
mode really rears its ugly head in this circumstance). So in that
instance, you cross connect like mad (and hence build your own mesh of
that sheet you should have laid down in the first place).

Most folks we hear from who don't complain about tuning (it loaded
fine, works fine, and lasts a long time) wail a tale of grief about RF
getting into their speaker, bathroom fault isolation, hall dimmer, VCR
- you name it, but it isn't called a tuning problem fer sure.

We ask them to jumper in an extra few feet of transmission line and
check their SWR. They usually are astonished that their antenna needs
tuning again. This is a slam dunk indication of common mode problems.

Like I said, these complaints are not uncommon. On the flip side,
some folks think more tingle on the lips is simply their excitment of
working DX (whose going to complain about that?).

73's
Richard Clark, KB7QHC