On Sat, 16 Aug 2003 09:38:18 GMT, Richard Clark
wrote:

On Sat, 16 Aug 2003 07:07:16 GMT, "George, W5YR"
wrote:

Richard,

It always astounds me how the technically challenged are wont to launch ad
hominem attacks instantly

Do you accept that yours similarly deflates your credentials? It
would at least place us on equal footing - in the gutter I suppose,
but I brought my snorkel. ;-)


73/72, George

Hi George,

If you suffer the heat of taking a stand, so much for a test of faith.
I have not seen you respond to the chain of evidence I have supplied
to these matters. I will offer that this body of work long preceded
my missive. You might or might not find that work
interesting/correct/or worthy of your attention, but that does not
erase if from the archive nor detract its intrinsic merit in desired
measure to bruised ego.

Pick any ONE of your cherished notions that I so soiled and put it up
for a clear and concise examination.

OR

Let me head that off with a very simple question that most dodge; and
in fact lies at the very heart of your subject line:
Given the premise that the amateur's rig output Z is NOT 50 Ohms, what
value does it have (cite any assembly of conditions)?

You will no doubt get many thumps on the back from well-wishers who
spit in my direction. How many will offer a numeric response to that
technical enquiry? I can forecast that will stand at the current
exchange rate of 0. I will also forecast there will be either total
silence, or scattered muttering about why they wouldn't engage such a
scurvy fellow as me. And yet the absence of that number from the
discussion under this subject line mocks the charter of this group
more than my humor did you.

Is it lower than 50? Higher than 50? How much? The stunned silence
in response to such simple, forced speculation is more a result of
intellectual catatonia than moral indignation.

Those who have offered numbers (I count among them), who have revealed
methods of their derivation (I count among them), who performed actual
bench work (I count among them), who offer rationale as to the
subject's correlation to other observables (I count among them) is
notable in contrast to those who have nothing to show but the shallow
rhetoric of impotent denial.

73's
Richard Clark, KB7QHC


Hi All,

I note by the absence of response that at least my mystical powers of
clairvoyance are unparalleled. No one dare step up to the bar to
answer the question:

"What is the Z of a transmitter, if it is not 50 Ohms?"

For those who would rather argue the mystic ability than answer the
question, I will allow that this same absence may be due in part to
the Blaster virus and the power black out. Now that I've braced up
your crutches, let's proceed with a telling example of both the
academic principle and the practical implication.

I will simply choose a value for you. In other words, we will venture
where these angels fear to tread. We will start with a deliberately
mismatch transmitter, and a deliberately mismatched load. We will
then throw in the practical necessity of line loss and ask the
question that is my acid test for the wide-eyed inventors:

"Does it make more than 1dB difference?"

The scenario begins:

"A 50-Ohm line is terminated with a load of 200+j0 ohms.
The normal attenuation of the line is 2.00 decibels.
What is the loss of the line?"

Having stated no more, the implication is that the source is matched
to the line (source Z = 50+j0 Ohms). This is a half step towards the
full blown implementation such that those who are comfortable to this
point (and is in fact common experience) will observe their answer and
this answer a

"A = 1.27 + 2.00 = 3.27dB"

"This is the dissipation or heat loss...."

we then proceed:

"...the generator impedance is 100+0j ohms, and the line is 5.35
wavelengths long."

"A = 1.27 + 2.00 + 1.62 = 4.9 decibels"

Thus the answer to my question is:

Yes. 1.62dB is greater than 1dB.

Now, as to the application of this knowledge to the typical user. It
becomes: "does my standard of 1dB meet the thresh hold of your
caring?" Perhaps not and even 3 dB may be of no concern. For such
folk I offer my best wishes and we each proceed happily on in life.
[This, of course, presumes they do not in fact have a rig that
exhibits a 600 Ohm output Z and hence the danger of nay saying the
obvious without expressing a value to replace it.]

Now, as to the application of this knowledge to the critical user. By
this I mean those here who want to have a complete answer, and being
thus informed can make their own choices. Is there anyone
corresponding here that want to dispute that this is the charter of
this group?

I have then twice shown how a transmission line being bound by two
reflecting planes introduces a Mismatch Uncertainty. This example has
enlarged on that slightly through my advice that this uncertainty can
be reduced to zero through the description of all paths. As I have
also pointed out in the past, this is a simple truism of wave
interference math - very simple.

The fact of the matter is that nearly every correspondent to this
forum employs a transmitter designed to and exhibiting 50 Ohms source
Z. The simple fact of the matter is that none of those same
correspondents will typically encounter that additional 1.67dB because
of this. Those who choose to operate their transmitter outside of
this specification may; but those same operators rarely, if ever,
examine the evidence of Mismatch Uncertainty because they never move
their load nor their SWR meter (the path never changes). They instead
will observe a reading in their complacency and accept the error
without being aware (unless they have read this, that is).

I will add that even when operating outside of the characteristic
source Z, that is not significantly off enough to match the issue
portrayed above unless you cut power dramatically - and even then the
issue is moot even though the loss is not.

So, part and parcel to the subject header above and having shown how
ignorance and rejection of the obvious has a concomitant loss; the
question, as always, remains:

Given the premise that the amateur's rig output Z is NOT 50 Ohms, what
value does it have (cite any assembly of conditions)?

What constitutes the silence from this point on? My proven
clairvoyant skill being elevated by the day, the Blaster virus, the
power outage, or that same intellectual catatonia?

73's
Richard Clark, KB7QHC