On Thu, 28 Aug 2003 12:18:44 -0500, W5DXP
wrote:

Richard Clark wrote:
So, Cecil (George, Peter, et alii), do you have an answer?

Years ago, I had a discussion with Jeff, WA6AHL, here on this
newsgroup. I suggested that the impedance looking back into
the source might be Vsource/Isource, i.e. the transformed
dynamic load line. However, I have never taken a strong stand
on source impedance. If reflections are blocked from being
incident upon the source, as they are in most Z0-matched
systems, the source impedance doesn't matter since there
exists nothing to reflect from the source impedance.

My basic approach is to achieve a Z0-match and therefore
forget about source impedance.

Hi Cecil,

That's all fine and well. It exhibits a rather standard behavior and
confirms conventional expectations. I take by this response that you
have no interest in the confirmation of interference in both Optical
and RF metaphors being visited at the bench. That is fine too. It is
a rather tough example to replicate - except when stumbled upon, then
we hear cries for exorcism being needed (my cue).

My missives simply offer touchstones of clarity in contrast to the
murky sea of un-fettered statements. We are presented with fantastic
notions that the characteristic source Z of a transmitter is
unknowable, and this statement is usually closely allied to the notion
that this same "unknowable" Z is actually responsible for reflecting
all power arriving at the antenna terminal. Few of those who utter
these witless jokes have any response to the straight line "So what is
this Z that does all that reflecting?" In their chagrin, they fail
even to repeat "it is unknowable...." Absolutely none can venture a
guess that it is either: "much less than 50 Ohms," or it is "much more
than 50 Ohms." This would be two obvious rejoinders and yet neither
is uttered. Such is faith. The universal silence condemns their
specious claims absolutely.

These absurd notions deserve a hearty laugh, because it invalidates
the need for a tuner which is purposely inserted between the source
and load to serve that very purpose (and which you describe as your
typical habit which is a nearly universal application).

But, again, this discussion is generally reserved only for those
interested in accuracy. :-)

73's
Richard Clark, KB7QHC