"Mike Andrews" ) writes:
Chuck Harris wrote:

Today it is trivial to make a simple switching power supply that can provide
a couple of hundred volts at 98% efficiency, why not make one of them, and
use some real tubes?

The problem I've encountered with switching supplies is that they're so
blasted noisy because of the fast risetimes in the high-current parts
of the supplies and because they're usually not very well shielded and/
or decoupled.

But given the topic, I'm always surprised that people don't treat switching
supplies like those cars of old. Look in the old ARRL mobile manual (and
a later edition just might have a receiver using those 12v tubes), and
there was always material about filtering the alternator noise.

Make it go through feedthrough capacitors, put in tuned circuits in
series with the 12V (to null out the whine), and good shielding. These
are the things that apply to switching supplies, though too often they
are so treated as black boxes that nobody considers such things.

As for 12v tubes, you most certainly saw converter using them. SOmeone
was asking about 12v Nuvistors a while back, and the next to last edition
of the ARRL VHF Manual, late sixties or so, has a converter using one.


Michael