Roy Lewallen wrote in news:1323ikbgpa8cfb6
@corp.supernews.com:

K7ITM wrote:

I want to bring up another reason to be very careful to even call them
"virtual shorts." They are virtual shorts only at certain
frequencies. To me, that is a very important distinction. Keeping
that frequency dependence in mind helps me be ever aware that they are
not anything like a real short.

And only in steady state. And only in one direction. Yes, care in
needed.

It is simple inadequate models that lead to the thinking:

In the presence of mismatch, there is a reflected wave.

The anode glows red under mismatch, it obviously is caused by the power
reflected from the antenna mismatch. (The observation is only made when
the anode is red, so since the anode being red is always associated with
a mismatch, then it is believed that mismatch always causes the anode to
glow red, even though that is not a logical conclusion. The element of
danger to equipment reinforces this, and elevates it to the status of a
law.)

One solution is to insert an ATU near the transmitter, it works by re-
reflecting the power in the reflected wave so it is all goes to antenna
and totally radiated, thats what it is all about, getting all the
transmitter power up the stick, how else could it work, the reflected
power doesn't reach the transmitter any more. The anodes run cooler,
clear proof that the explanation is sound.

ATU is really a misnomer, it doesn't tune the antenna at all (we all knew
that), it is really a total-re-reflector when you have the true insight.

We have to remember that in the absence of good models of transmission
line behaviour (eg quantitative models), people will try to fit models
that they can understand, good or bad. If the path from mismatch to red
anodes is too complicated, simplify it, leave all the intermediate
explanation and conditions out, cut to the chase, what is the outcome,
make it a rule.

I agree with you Roy. I think that inventing explanations that are based
on things that aren't or don't happen is satisfying the learner's quest
for knowledge with potentially false information that must be unlearned
to move forward. Worse is that these kearners seize upon these inadequate
models and propagate them, the new experts of ham radio.

One of the risks to ham radio of the new six-hour hams is our feeding
them with inappropriate and inadeqate dumbed down models. I suppose it is
not new, this is probably the root of most of the myths of ham radio (eg
resonant antennas always work markedly better... make it resonant and it
will improve out of sight).

Owen