Regarding the SWR "meter" on the front panel of your transceiver -

Where is the transmission line on which the "measured" SWR is supposed to
lie.

Transmission line is not required in order for RF power to be reflected. If
nothing is connected to the transmitter output connector, then all the power
the tx is trying to produce will be reflected at that point. Return loss
will be zero, and the reflection coefficient will be 100% with respect to
that interface. The equivalent of those parameters in terms of SWR is
"infinite." Barring RF power foldback coming into operation, whatever
circuits that ARE part of that scenario will see additional, and possibly
damaging energy levels.

What do you do with the SWR when you think you know its value? What
further
calculations can it participate in? What else does it tell you which you
don't already know?

Circuit parameters more easily can be adjusted to reduce losses and improve
the safety margins for the RF components in the output system.

I respectfully suggest the whole thing exists only in your imagination and
what you are *really* interested in is whether or not the transmitter is
loaded with its designed-for resistive load, usually but not always 50
ohms.

The mystery can be solved, confusion cleared, instead of lies newcomers
and
learners can be taught the simple facts of life just by changing the name
of
the useful little instrument to TLI in the handbooks.

Regarding prevention of meltdowns - good transmitter designers remember
to
incorporate a fast-acting fuse in HT supply.

If reflected power truly was imaginary, HT supplies wouldn't, as you
suggest, even _need_ a fast-acting fuse to (attempt to) protect them from
meltdown by RF load mismatches.

In any case, a good transmitter designer wouldn't rely on a fuse to protect
the tx from RF load problems. Fuses are OK, and commonly used for AC/DC
fault protection, but are not fast enough to minimize the damage to RF
output networks from high, short risetime mismatches such as arcing, etc.

RF

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