Richard Clark wrote:
"The presumption (forced or otherwise) is that the output is sinusoidal.
In fact, the cathode current of the amplifier proves quite positively
that only a pulse in, 180 degrees of sinewave, or even less, is
sufficient to generate a remarkably clean sinewave at the final`s
output."

That is a remarkably clear statement of the behavior of a Class C
amplifier. The amplifier acts as a generator of a sinewave which is
synchronized by its input signal instead of being an accurate reproducer
of the waveform at its input.

The less than half wave of current flow of the Class C amplifier allows
an efficiency exceeding 50%. Walt Maxwell`s tests show that the Class C
amplifier sticks to the parameters of a Thevenin source.

The question of "what is the source impedance" presented to a load by
the amplifier? is answered, not by magic, but by the maximum power
transfer theorem. The amplifier must be adjusted to deliver all its
available power. Then, the output impedance of the amplifier is simply
the conjugate of the load impedance which is easily measured.

Best regards, Richard Harrison, KB5WZI

On Wed, 18 Jun 2008 03:39:54 -0500, (Richard
Harrison) wrote:

The question of "what is the source impedance" presented to a load by
the amplifier? is answered, not by magic, but by the maximum power
transfer theorem. The amplifier must be adjusted to deliver all its
available power. Then, the output impedance of the amplifier is simply
the conjugate of the load impedance which is easily measured.

Hi Richard,

MPT Conjugate Match Z Match

You can NOT achieve the COMBINATION of any two, much less all three
with a Class C amplifier. This is like checking all three possible
answers on a multiple choice exam. It follows that source impedance
has not been answered here as a qualifiable (which is certainly not
what I was looking for).

I will take it that you don't know what the source impedance is as a
quantifiable either. That is, unless you unwind all the confounding
statements and remove those in error. There cannot be three,
simultaneous quantifiables of differing values.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
news
On Wed, 18 Jun 2008 03:39:54 -0500, (Richard
Harrison) wrote:

The question of "what is the source impedance" presented to a load by
the amplifier? is answered, not by magic, but by the maximum power
transfer theorem. The amplifier must be adjusted to deliver all its
available power. Then, the output impedance of the amplifier is simply
the conjugate of the load impedance which is easily measured.

Hi Richard,

MPT Conjugate Match Z Match

You can NOT achieve the COMBINATION of any two, much less all three
with a Class C amplifier. This is like checking all three possible
answers on a multiple choice exam. It follows that source impedance
has not been answered here as a qualifiable (which is certainly not
what I was looking for).

I will take it that you don't know what the source impedance is as a
quantifiable either. That is, unless you unwind all the confounding
statements and remove those in error. There cannot be three,
simultaneous quantifiables of differing values.

73's
Richard Clark, KB7QHC

Hi Richard C,

Am I hearing you correctly? Are you disagreeing with Richard H? Are you saying
that maximum power transfer, conjugate match at the output, and Z match cannot
occur simultaneously? Are you serious? As I understand Everitt's statement of
the maximum-power-transfer theorem, when the maximum available power is being
transferred to the load there is a conjugate match. Does this not also mean
there is a 'Z' match? Can't 'Z' be assumed to be the impedance of the source as
well as the load?

Walt, W2DU

On Wed, 18 Jun 2008 11:59:40 -0400, "Walter Maxwell"
wrote:

Hi Richard C,

Am I hearing you correctly? Are you disagreeing with Richard H? Are you saying
that maximum power transfer, conjugate match at the output, and Z match cannot
occur simultaneously?

Hi Walt,

For a Class C tube amplifier.

All descriptions of tune-up for a Class C tube amplifier describe a
qualitative MPT as this classic method offers absolutely no
information about the quantitative degree of initial mismatch, nor
subsequent proximate match. In other words, there are no quantitative
values of load impedance revealed by this method. It may even be said
that the classic tune-up only describes "an attempt" at MPT; as it
may, in fact, not even achieve anything more than Mediocre Power
Transfer. After peaking the grid and dipping the plate, I have
observed many different peaks and dips for many various loads to know
that not all loads obtained all available power.

The classic description of a tune-up is based on qualitative
assumptions and the amplifier is brought into its best attempt, which
is not demonstrably efficient, nor even proven to be "matched"
conjugately or by impedance. This takes more information (so far
unrevealed) obtained by current into the known load (unrevealed), and
power into the source (unrevealed). No one other than myself has
expressed the loss of the source because no one else has ever
enumerated its resistance (a topic commonly hedged and avoided) Hence
discussion of efficiency is lost in the woods and correlation to
MPT/Z/Conjugation is equally doomed to ambiguity.

Are you serious? As I understand Everitt's statement of

Everitt notwithstanding, Lord Kelvin trumps him with
"when you cannot express it in numbers, your knowledge is of a
meagre and unsatisfactory kind"
This thread has suffered from a lack of measurables that are not that
difficult to obtain.

So, to return to my very specific question:
What is the source resistance of any power amplifier?
I will further loosen constraints (if that isn't loose enough)
For any match?

One complex number is sufficient, and certainly that value will
resolve all imponderabilities is what I am asking for.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 18 Jun 2008 11:59:40 -0400, "Walter Maxwell"
wrote:

Hi Richard C,

Am I hearing you correctly? Are you disagreeing with Richard H? Are you
saying
that maximum power transfer, conjugate match at the output, and Z match
cannot
occur simultaneously?

Hi Walt,

For a Class C tube amplifier.

All descriptions of tune-up for a Class C tube amplifier describe a
qualitative MPT as this classic method offers absolutely no
information about the quantitative degree of initial mismatch, nor
subsequent proximate match. In other words, there are no quantitative
values of load impedance revealed by this method. It may even be said
that the classic tune-up only describes "an attempt" at MPT; as it
may, in fact, not even achieve anything more than Mediocre Power
Transfer. After peaking the grid and dipping the plate, I have
observed many different peaks and dips for many various loads to know
that not all loads obtained all available power.

The classic description of a tune-up is based on qualitative
assumptions and the amplifier is brought into its best attempt, which
is not demonstrably efficient, nor even proven to be "matched"
conjugately or by impedance. This takes more information (so far
unrevealed) obtained by current into the known load (unrevealed), and
power into the source (unrevealed). No one other than myself has
expressed the loss of the source because no one else has ever
enumerated its resistance (a topic commonly hedged and avoided) Hence
discussion of efficiency is lost in the woods and correlation to
MPT/Z/Conjugation is equally doomed to ambiguity.

Are you serious? As I understand Everitt's statement of

Everitt notwithstanding, Lord Kelvin trumps him with
"when you cannot express it in numbers, your knowledge is of a
meagre and unsatisfactory kind"
This thread has suffered from a lack of measurables that are not that
difficult to obtain.

Richard, are you inferring that I have not submitted the measurables required to
determine the source impedances of the xmtrs I measured? What additional
measureables that I haven't already submitted are you asking for to prove the
source impedances that I've already submitted are valid?

So, to return to my very specific question:
What is the source resistance of any power amplifier?

Richard, the source impedance of one of the xmtrs I measured with load impedance
of 17.98 + j8.77 ohms measured 18 - j8 ohms. Considering measurement error,
wouldn't you agree that these two impedances qualify for a conjugate match, and
that this value of source impedance is valid at least within the realm of
possibility?

For any match?

One complex number is sufficient, and certainly that value will
resolve all imponderabilities is what I am asking for.

OK, Richard, is impedance 18 - j8 ohms sufficient?

Richard Clark, KB7QHC

Walt,W2DU

On Wed, 18 Jun 2008 17:16:59 -0400, "Walter Maxwell"
wrote:

OK, Richard, is impedance 18 - j8 ohms sufficient?

Hi Walt,

It is more direct and responsive to every request I've made for
anything from anyone else so far. However, I presume it is the value
at the antenna connections of the amplifier that transforms through
the plate tuning toward the plate itself to render something more like
Rp (several KOhms?). Is it from a direct measurement, or by inference
to the load and tuning adjustments?

73's
Richard Clark, KB7QHC

Richard Clark wrote:
"I presume it is the value at the antenna connections of the amplifier
that transforms through the plate tuning toward the plate itself to
render something more like Rp (several KOhms?"

Rp has nothing to do with a Class C amplifier which acts like a switch
presenting an impedance to average current flow by being open-circuit
most of the time.

Best regards, Richard Harrison, KB5WZI

Richard Clark wrote:
"What is the source resistance of any power amplifier?"

Most power amplifiers are designed for a specified load but include
controls to adjust their outputs, both resistance and reactance, so that
a load which deviates can be made to match the 50-ohm or 600-ohm load
specified for the transmitter.

Am broadcast stations in the USA have a point at the transmitter output
just before power branches out to antenna system elements called the
"common point". Impedance here has been adjusted to a specified
resistance and a thermocouple ammeter is routinely installed which is
used to determine that the specified power output is being delivered by
the station by I squared R according to the FCC allocation. There is a
multiplier specified of 0.92 for stations of 5 KW or less. For stations
more powerful than 5 KW the multiplier is 0.947. This multiplier allows
for a slight increase in power to offset misc. errors and losses.

John E. Cunningham writes in "The Complete Broadcast Antenna Book" on
page 51:
"Suppose for example, we have a transmitter that is designed to work
into a 50-ohm load at an efficiency of 70% (Fig. 1-26). The efficiency
of this circuit expressed as a decimal, is given by

eff = RL / RS + RL

Rearranging

RS = RL [1/eff - 1]

Substituting the numbers inti this, we get

RS = 50 [1/0.7 - 1] = 50(1/0,7 - 1) = 50(0.43) = 21.4 ohms

You have an example in numbers. Hope you are happy.

Best regards, Richard Harrison, KB5WZI

On Wed, 18 Jun 2008 16:53:43 -0500, (Richard
Harrison) wrote:

RS = 50 [1/0.7 - 1] = 50(1/0,7 - 1) = 50(0.43) = 21.4 ohms

You have an example in numbers. Hope you are happy.

Hi Richard,

As I mentioned to Walt in similar response to my oft-asked question:
direct and to the point. I see no others yet.

I know this wasn't arrived at by direct measurement and only by
inference. As I remarked to Walt (but in the inverse), I presume
this value is that transformed through the plate tuning from the
plate's Rp? Can you provide some work-up (presumably several KOhms)
from your citation for that?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 18 Jun 2008 16:53:43 -0500, (Richard
Harrison) wrote:

RS = 50 [1/0.7 - 1] = 50(1/0,7 - 1) = 50(0.43) = 21.4 ohms

You have an example in numbers. Hope you are happy.

Hi Richard,

As I mentioned to Walt in similar response to my oft-asked question:
direct and to the point. I see no others yet.

I know this wasn't arrived at by direct measurement and only by
inference. As I remarked to Walt (but in the inverse), I presume
this value is that transformed through the plate tuning from the
plate's Rp? Can you provide some work-up (presumably several KOhms)
from your citation for that?

73's
Richard Clark, KB7QHC

Richard, am I now to understand that you haven't reviewed my Chapter 19A, which
details the entire procedure I used for the measurements that include the
resistance RL = 1400 ohms at the input of the pi-network? If you haven't I can
understand the reasons for your questions. I urge you to read 'Section 19.14
Additional Experimental Data', the last portion of the Chapter which describes
in detail the procedure is used in the measurements made on a Kenwood TS-830S.
I'm sure you'll find the answers you're looking for there.

You can find 19A by using this url from Cecil,
http://www.w5dxp.com/Chapt19a.doc. It derives from the thread directly above
'Unwin Antennas'.

Walt, W2DU