Behold, Pete KE9OA signaled from keyed 4-1000A filament:

We were thinking of either LCD, or statically driven LEDs, with the
microprocessor going into sleep mode with no user activity. Oh, I do
like those knobs...........I wouldn't have it any other way. Anyway,
the problem with the flourescent displays is that they are pretty noise.
I plan on this receiver having an MDS of 40 to 50nV, so things have to
be pretty quiet. I think that I will also go with an outboard supply;
this avoids that UL qualification. Another advantage to this approach
is that my outboard power supply can be used with other people's
equipment. Take a look at the power supply on my website, and you will
see that it doesn't take much to design a quiet power supply. On my
general coverage receivers, even when operating off the AC line, when I
tune down to 9 or 10kHz, all I hear is atmospheric noise.

Gotcha on the noise factor. I don't multiplex, but use "static" driven
nixies, so I never thought of the noise.

I use outboard supplies on all my tube low-level audio designs like mic
preamps and mixers. Works awesome!

LCD's are cool. If you choose that route, may I suggest LED backlighting?
That would eliminate electroluminescent driver noise and last forever
compared to incandescent.

My #1 repair call that's not computer related lately is "my lights burned
out". I replace them all with superbright white LED's, or if the customer
wishes, a funky color of their choice :-)

--
Gregg
*Perhaps it's useful, even if it can't be SPICE'd*
Visit the GeeK Zone - http://geek.scorpiorising.ca