[Arny Krueger]

"robert casey" wrote in message

OTOH, its my recollection that their use of filament
power was about the same as regular tubes. I do remember
that they used DC on the filaments.

Oh sorry, I meant to talk about directly heated filament
tubes (where the filament is the cathode), not the tubes
with indirectly heated cathodes.

It appears that indirectly heated cathodes are pretty much a prerequisite
for maximum linearity. The tubed equipment I worked on was designed in what
many around here would think is an odd way - it was designed for maximum
possible accuracy. Something about wanting to hit the aircraft or missile
that was attacking before it hit you! ;-)