On Wed, 28 Feb 2007 13:55:47 -0800, Jim Kelley
wrote:

What I meant was, in what way were you able to attribute and apportion
this heat to its various sources? What evidence were you able to
obtain to show reflected energy re-entering the source output? What
component in the system in fact dissipated the reflected energy? How
were you able to determine the exact source and amount of energy at
any given location within the source? Or did you just presume that
you understood the underlying mechanisms?

Hi Jim,

This knowledge arrived by many avenues.

For one, in a heavily heatsinked design, mapping of temperatures
generally reveal a very diffuse origin. That, of course, is the
purpose of the heatsink. So, in that regard the assignment of where
dissipation occurs is done by induction. You can eliminate a lot
circuitry as being incapable of supporting this dissipation, as it is
both remote from the signal path, and remote physically. The
literature of design reveals much of what is discovered in the field.

That literature reveals the dissipation occurs in the
emitter/collector junction of the finals' transistors. Failures have
been confirmed through post-mortem examination by microscope (no, I
have not done this).

Experience with new designs and frequency of failure (those activities
that I have participated in) lead to the same conclusion. In one
particular case it was a manufacturing/assembly problem of mounting
the transistor to the heatsink. A bur was found in many such mounts
that interfered with a complete mating of surfaces. This raised the
thermal resistance in the path from that same junction to the mating
surface, to the heatsink, to the environment. Knowing each thermal
resistance in that path makes it rather simple to forecast the
junction temperature at the time of failure (or rather, to say failure
which occurred was guaranteed a fatal temperature) when you know the
power consumed by the component. All such "resistance" conform to the
simple math of Ohm's law (once you substitute the necessary units for
heat).

When we return to the design guidelines and this junction, almost
every manufacturer of power transistors specifies a junction
resistance value at rated power. Casting this value through the chain
of transformations and to the antenna connector reveals a value very
nearly 50 Ohms. There are newer power amplification designs today,
and yet the market for Ham gear is dominated by the Class AB design
which is exhibits this property nicely.

Inductive logic leads us to this junction as the principle target of
reflected power (the signal path is symmetric, after all). Experience
has supported this logic. Failures are attributable to design flaw
(or assembly flaw), or poor application (driving a mismatch), or both.

As for tubes, I've already testified to the obvious location for
dissipation. It is far easier to see.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On Wed, 28 Feb 2007 13:55:47 -0800, Jim Kelley
wrote:


What I meant was, in what way were you able to attribute and apportion
this heat to its various sources? What evidence were you able to
obtain to show reflected energy re-entering the source output? What
component in the system in fact dissipated the reflected energy? How
were you able to determine the exact source and amount of energy at
any given location within the source? Or did you just presume that
you understood the underlying mechanisms?


Hi Jim,

This knowledge arrived by many avenues.

But primarily, it seems, by speculation. I know how to measure heat,
Richard. What I am asking, and what you have thus far been unable to
answer (which is as I suspected), is how is it that you were able to
ascertain that this heat energy was caused by energy that was
reflected from the load rather than having come directly from the
power supply within the source? How is it that this electromagnetic
energy is so easily reflected from a load, but is utterly immune to
reflection when it encounters the output of a source? I think it's
been fairly well established that the output impedance of these things
is far from 50 ohms. Why should reflected energy not be, at least in
some part, re-reflected back toward the load?

Someone who alleges to be so familiar with load lines should be able
to contend with an increase in dissipation against a mismatched load
without having to explain it as 're-absorbed' reflected energy.

Inductive logic leads us to this junction as the principle target of
reflected power (the signal path is symmetric, after all).

Speculation could also lead to that juction.

Experience
has supported this logic.

It could be experience coupled with misattributed fact. Possible?

73, Jim AC6XG

On Thu, 01 Mar 2007 09:58:02 -0800, Jim Kelley
wrote:

, is how is it that you were able to
ascertain that this heat energy was caused by energy that was
reflected from the load rather than having come directly from the
power supply within the source?

In the theological sense, this predicates that power never becomes
dissociated from "the source." That is ambiguous, isn't it?

Is that to include the batteries behind the collector supply? The
power supply charging the batteries? The power grid feeding the power
supply? The generator driving the grid? The Coal firing the steam
spinning the generator? The sun through photosynthesis growing plants
to provide the coal? The previous supernova that seeded the cosmos by
which coalescence formed the sun? ...and into an infinite regression
to that previous supernova?

The energy dissipated is computed from the Galactic Load Line.

I think it's
been fairly well established that the output impedance of these things
is far from 50 ohms.

Can you offer what that complex number is? :-0

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On Thu, 01 Mar 2007 09:58:02 -0800, Jim Kelley
wrote:


, is how is it that you were able to
ascertain that this heat energy was caused by energy that was
reflected from the load rather than having come directly from the
power supply within the source?


In the theological sense, this predicates that power never becomes
dissociated from "the source." That is ambiguous, isn't it?

Is that to include the batteries behind the collector supply? The
power supply charging the batteries? The power grid feeding the power
supply? The generator driving the grid? The Coal firing the steam
spinning the generator? The sun through photosynthesis growing plants
to provide the coal? The previous supernova that seeded the cosmos by
which coalescence formed the sun? ...and into an infinite regression
to that previous supernova?

The energy dissipated is computed from the Galactic Load Line.

Sarcasm clearly noted, and surprisingly uncalled for. I'll try asking
one more time. It is a simple metrology question: How were you able
to directly ascertain that the heat being dissipated in the source was
produced by energy being reflected from the load?

Thanks,

Jim, AC6XG

On Thu, 01 Mar 2007 11:27:36 -0800, Jim Kelley
wrote:

Sarcasm clearly noted, and surprisingly uncalled for.

Hi Jim,

I responded in kind is all, you revealed a trap and I jumped into it
with both feet. If that broke it, return it to the vendor for a
refund.

Is power/energy separable from its source? If this question is
obnoxious, why did you raise the prospect?

When it is generally accepted that our sources do not exhibit 50 Ohms
source resistance/impedance, what resistance/impedance do they
exhibit? If you don't have an answer, what was the purpose of this
uninforming assertion?

If these two questions have the trappings of sacrasm, I did not
originate their discussion. And putting your mock-shock aside, they
are part of the chain of denial you are adding links to, aren't they?

73's
Richard Clark, KB7QHC

Richard Clark wrote:

Is power/energy separable from its source?

What other point is there to attaching an antenna to a transmitter?

73, Jim AC6XG

On Thu, 01 Mar 2007 14:28:58 -0800, Jim Kelley
wrote:

Richard Clark wrote:

Is power/energy separable from its source?

What other point is there to attaching an antenna to a transmitter?

Hi Jim,

I will take that as an affirmative.

When it is generally accepted that our sources do not exhibit 50 Ohms
source resistance/impedance, what resistance/impedance do they
exhibit?

73's
Richard Clark, KB7QHC