This is another example of the problems that can result from
misunderstanding the term "mismatch loss". People have been talking
about its reciprocal (or negative, in dB) here, and calling it
"reflection gain", a term I hadn't heard before but I don't doubt the
term is legitimate.

I've posted fairly extensively about "mismatch loss" on this newsgroup.
You should be able to find the postings easily with a Google search. The
main point is that "mismatch loss" (and its reciprocal "reflection
gain") don't really represent loss in the dissipative sense, but rather
"power that coulda been but ain't". It's a useful concept, but one just
asking for misinterpretation and misuse by people who don't really
understand what's happening. Hopefully a look at my previous postings
will clarify the matter for you. Once you understand what "mismatch
loss" really is, the concept of "mismatch gain", or "reflection gain" as
it's being called, should be easy to comprehend.

Roy Lewallen, W7EL

Yuri Blanarovich wrote:
In itself, it the tuner has I^2R losses to be sure, but if the antenna
radiates 100 watts with the lossy tuner in place and only 20 watts without
it, how wrong it is to claim an insertion gain of 80 watts for the tuner?


Very wrong!
Tuner is not attributing gain to nothing. It has losses due to losses in its
components, doesn't matter how you slice it.
When you match antenna to transmitter output (especially solid state 50 ohm
type) and make transmitter happy to produce full 100W output, you are not
adding "gain" from/by the tuner.
That transmitter when looking to mismatched load cuts power back to 20W, when
you insert tuner, you are not making up 80W in the tuner (gain?) but making
transmitter produce full output. You are now putting 100W in and getting some
90W out, 10W lost in the tuner, but antenna is getting 90W from the combo.
Where is the gain in the tuner?
Looks like things are getting ridiculous here. No tuner (passive) has a gain,
it has always loss.

Yuri