On Mon, 12 Mar 2007 11:00:04 GMT, Jan Panteltje
wrote:

Also normally, there is a pi type filter (to prevent harmonics), between
amplifier and antenna.
This filter _WILL_ match the antenna to the output impedance of the
transmitter, so _even_ if the transmitter output impedance is very
very low (low voltage high current output stage for example), the reflected
power will be nicely converted to match the transmitter, and heat up the
output amp, with its possible destruction as result.

Hi Jan,

Actually, there is a transformer there in the typical Ham transmitter
(and probably in every general purpose power source) that typically
transforms the native Z to the output Z. This is a step up for solid
state, and step down for tubes. In the solid state rigs, it is a
literal transformer feeding the 1-2 Ohms through a 5:1 winding ratio
to a switched bank of low pass filters. This stuff is mud ordinary.

As for the reflected energy, depending upon the phase it will either
combine destructively (heat) or constructively (cool) in the extremes.
There are, of course, 179 degrees of variation between these extremes
before they repeat themselves again. Cooling, of course, is something
of a misnomer as nothing useful is happening (poor power transfer) so
perhaps the terms should be destructive through uselessly benign.

73's
Richard Clark, KB7QHC