Back when we used tubes I remember that the plates would glow red
then white hot depending on a few factors one of which was how the
output pi filter was tuned, For them that don't remember the output pi
filter tuned the output of the plate circuits (usually about 50k) to
the 50 ohms that the coax liked, hopefully the antenna was 50 ohms
also. So the finals were affected a lot by the swr they saw and we
could see it also just by the color of the glow, white meant better
shutdown and retune or just retune without shutting done.






How do you know that you have a better signal when you tune your
antenna for lowest SWR?

An SWR meter is good for telling you when your transmitter is seeing a
flat 50 ohm load. It is useful as a tuning device. Not much more.

Solid state finals don't like complex impedance's. It causes them to
draw excessive currents. High SWR goes along with reflected complex
impedance's. Also the output circuit is usually fixed at 50 ohms. If
you don't match that you will not get maximum power transfer from the
transmitter.

Your solid state transmitter usually has a power reduction circuit
that reduces power out when it sees a high SWR. So having the proper
match at the transmitter will ensure full power out.

On tube transmitters you will usually not find any high SWR protection
circuits. Tubes are very tolerant on complex impedance loads.

As explained in the ARRL HANDBOOK, reflected power does not reach the
finals in your transmitter. See below again.

Regards
Gary