John Higdon wrote:

You have to ask yourself if the unit, properly tuned, might be better in
terms of efficiency and component longevity in "normal" mode than in the
parameter-limiting "tune" mode. It's a distinct possibility.

That is, in fact, why I was posting. It looks like they are just changing
the screen grid bias, so I could imagine some situations where that could
be the case.

I am assuming that if I really wanted to reduce the power, the sane thing
to do would be to reduce the B+ voltage to the final?

Not only that, if I set the antenna coupling for reduced power, is that
going to extend the life of the finals?

It could, assuming you don't kill the efficiency of the output stage.
One of the arts tuning up any transmitting device is finding the sweet
spot in terms of plate current, grid drive, and stage coupling. The
Harris MW-5 transmitters were notorious for having a narrow range of
final plate current and drive. Operate outside that range, and your tube
life drops precipitously, even though from a raw tube-spec point of
view, everything was well within limits.

Yup. I was hoping to find someone old enough to remember setting these
things up for regular use. I dragged this one out and started cleaning it
up because the 160 MHz auxiliary channels are totally unused in our area,
and the 950 Mhz stuff is very crowded. And you know, this thing doesn't
sound bad. Down 3dB at 8 Khz which may be a transformer issue.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."