On Wed, 28 Feb 2007 07:15:38 -0800, Jim Kelley
wrote:

Not that I dispute anything here necessarily, but I would like to know
how you went about measuring the reflected power dissipated within a
source. Also, how the power being dissipated?

Hi Jim,

Dissipation is caloric, however it can arrive catastrophically by one
of two mechanisms; and they reflect, no pun here, the two types of
phase sense offered by the random opportunity (being phase adding or
subtracting for current or voltage as the occasion demands).

One caloric method is simple in measuring the heat load expressed by
airflow temperature measurements in a confined volume. When I
designed the Flight Recorder, the FAA mandated a heat budget for its
acceptance. This is certainly far afield from the immediate topic,
but it responds to the attention offered in design to this issue. The
point of this sidebar is that efficiency translated immediately into
temperature and this was rigorously anticipated and tested. The same
design philosophy is mandated in RF final design and considerable
attention has been devoted to it in the trade papers.

Returning to our concerns, for certain phase combinations that caloric
solution can arrive suddenly in the form of an arc. Most operators
will immediately act to correct that situation and the heat build up
may not be great, but the damage may still be irreversible. This
harkens back to my discussion of a kitchen table laser cracking a
window pane. Average power may be unspectacular, but instantaneous
power, localized, can be very dramatic and destructive beyond
expectation (it certainly surprised my friend).

For other phase combinations that caloric solution can arrive
gradually (heat soaking); and catastrophe arrives through thermal
runaway. Operators rarely observe this until it is too late.

I hope that the readers can differentiate between these two, and how
certain designs (eg. solid state, and tube design) respond in these
cases and correlate to experience each to their own characteristic
failure mechanism.

73's
Richard Clark, KB7QHC