Owen Duffy wrote:
"Sal M. Onella" wrote in
:

as heat somewhere in the system. If too much is reflected back from
the antenna and dissipated within in your transmitter, the transmitter
overheats ($$$) or it reduces power to protect itself and nobody hears
you.

Here we go again!

If he said "sometimes overheats", he would be correct.
An SWR of 10:1 certainly *can* cause an over-current condition
in an unprotected transmitter assuming the reflected current
is in phase with the forward current at the transmitter.

However, just as likely is that the reflected voltage is in
phase with the forward voltage at the transmitter and an
over-voltage condition *can* result in punch-through of the
final transistor.

If over-current and over-voltage were not a problem caused
by reflected waves, protection of the finals would not be
necessary.

Note that the impedance seen by the transmitter above is a
*virtual* impedance, not an impedor. Virtual impedances are
only a *result* and not the cause of anything. Virtual impedances
are not the *cause* of over-current or over-voltage conditions.

Anyone who scoffs at virtual opens and virtual shorts being
the *cause* of the re-reflection of reflected energy cannot,
without contradicting himself, turn around and argue that
the virtual impedance seen by a transmitter is the *cause* of
the mismatch. One cannot have it both ways.
--
73, Cecil http://www.w5dxp.com