Ahhh! Finally some meat... SORRY,... LONG POST WITH MUCH techincal MEAT IN
IT...


"Richard Clark" wrote in message
...
On Tue, 25 May 2004 02:59:52 GMT, "Henry Kolesnik"
wrote:

Richard
...(what is) the "mechanism" in
the transmitter (such that) it can't
dissipate a reflection because there's some kind of one way
....checkvalve...reflects.
tnx

Hi Hank,
...
It can also reflect (some or all of) what it does not absorb, ...
is determined by the ratio of its Z to the line/load
at the antenna terminal. (Of the transmitter, I believe you mean)

Fine point: I think it must reflect ALL it does not absorb.
Important point: However, I believe the case is that it absorbs little
of this energy.

In this case (bear with me), the source Z is
NOW found at the load's mismatch, transformed through the line. This
means matching works both ways (often the singlemost ignored aspect of
obvious reciprocity in any of these arguments). Such circuit analysis
is called superposition.

Yes, no argument. Matching does, er um, CAN work both ways on the line,
is true. And the TX is, indeed, a "load" for the reflected energy (or wave
if you prefer).
I say CAN because the match does work both ways, but that is not to
imply that the impedances which exist on the line are matched - nor that one
way IS matched while the other is NOT. If there is a mis-match in one
direction, there will be another mismatch going the other way. This may be a
difficult to understand considering the "this situation must be matched"
mind-set we are in at this point, but I do not believe it is pixie dust,
however choose to skip it for now. See my conclusion at the end....
I think "superposition" is ther wrong term for this. If I could spell
reciprocity, I'd say that it is a better word.
Digression, though minor: Superposition refers typically, to the
application of two signals to a circuit and the resulting response being the
sum of the individual responses. no?


Now some meat I'd like to pursue...

...a 500 Ohm Source...you will never launch much power into a 50 Ohm
system because it would immediately hit a reflective interface at the
antenna connector.

There's a question I see here as to wheather the power was "launched" in
the first place and this may be part of the assumption (or set thereof)
which (my gut feel says) leads the logic astray.


This means that a 500 Ohm source, when confronted
by power going towards it from a 50 Ohm system will reflect most of
that power (but how did we get this power into the system in the first
place - Karma?) This, by design, will never happen in any transistor
ham rig built in the last quarter century.

I think this is true...BUT let's ask this same question of a 5.0 ohm
source?? How would you carry this through Richard C? I submit that THIS
source CAN launch significant power down the line.



...snip non technical stuff

The answer is the transmitter source Z is 50 Ohms at rated power.

OK, so now I see you are of the "Zs=50 ohms" camp.

If
a watt of power is chooglin' down the line toward it, that 50 Ohms is
going to dissipate into a watt worth of calories. This can be argued
with wave mechanics, or lumped circuit equivalents - doesn't matter
because it's all the same calories.

All ok with me _IF_ Zs=50. I'm not convinced however. I have to think
more about the modern broad-band transistor PA to have an strongly arguable
opinion on this concept.


Modern rigs can tolerate this...snip...

=== WARNING to the logic impaired, the following is a supposition ===

Now, lets simply accept those answers that require the magic pixie
dust

Uncalled for... I can make it work (so far though I am open) with the
electrical/electronic principles I think are true and work everywhere else.

of total reflection from the transmitter. Fine, the mismatched
antenna reflects some power, this power returns to the transmitter,
the transmitter simple routes it ALL back to the antenna,
round-and-round until the antenna finally radiates it. If this were
true, what do we need tuners for?

I think the answer here is that if the transmitter can take the strange
impedance it sees, then it isn't needed. Like Hanks 30L1 that, however,
couldn't take it very well.
Furthermore, there is an implicit assumption here in your reasoning
which I believe is key and leading to some error. There is an unspoken
assumption that the power which makes it to the antenna after all the "
round-and-round until the antenna finally radiates it" is the FULL output
and I believe it AIN'T. It is that little dribble that made it into the
line in the first place. a.k.a. the Tx is not generating the full output.
I think this assumption is causing much trouble.

Unless, of course, I have been smoking the wrong brand.

Comments R.C. ?

Steve