Modern Electronics (was Re: List charter mods & headcount...

21 Jun 2004

...
    I think
you would have problems with cross-talk between the
 open tubes, unless you limited your design to a single tube,
 or had large spaces between the tubes. 
There are plenty of multi-section valves around, with several electrode 
systems in the same envelope. Double triodes are really common, so are 
multiple diodes + a triode (like the EABC80 or UABC80 triple diode + 
triode (used in AM/FM radio sets for the AM detector, FM discriminator 
and 1st audio amplifier). And triode pentodes (either signal pentodes or 
output pentodes). In general the only coupling between the secions is due 
to stray capacitance.

...

 The glass does more than just hold the vacuum, it is also an
 insulator. 
Actually, it's not uncommon for it to be coated with a conduction film 
for electrical screening purposes.

-tony

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Modern Electronics (was Re: List charter mods & headcount...