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

From: John Lawson <jpl15_at_panix.com>
Date: Mon Jun 21 17:46:12 2004

On Mon, 21 Jun 2004, Kevin Handy wrote:

> Geoffrey Thomas wrote:
>
> >>This is more of what I'm getting at. Does it matter that some knowledge
> >>is lost as generations go on? Are we ever going to need to go back to
> >>tubes to design electronic circuits?


> >
> 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.
>
> The glass does more than just hold the vacuum, it is also an
> insulator. ^^^^^^^^^^^^^
> ^^^^^^^^^^
>
  sigh.... I ain't gonna get into a rant about modern electronics /
science "education" nowadays... but could perhaps I offer a small
logical trail, in response to the above assertion?

  If your tubes, envelopless, are already in an ambient vacuum -
interplanetary space, the surface of the moon, etc - pray tell me what
there is to 'insulate' against?

  What precisely, would be the mechanism of the 'cross-talk'?

  Now, granted, any electromagnetic, or even mechanical, disturbances
could still be propagated between these envelopless tubes, but this holds
true whether or not the glass is there.

  To pick nits, there would be added element structure suppport issues, as
many tubes use the inside of the envelope to support the micas, or other
parts, but that is a mechanical design problem, and does not bear on the
actual operational characteristics of the said envelopeless,
designed-to-operate-in-an-ambient-vacuum thermionic emission active
device.

  I have participated in the design of more than one 'tube', which we
built on the base of a bell-jar, then pumped down to check the operation,
then re-admitted atmosphere to make adjustments - as in fact most tube
design work is done (at the physical prototype level). Nothing changes
electronically, physically there are plate heat radiation differences,
some exposed element effects... but I can tell you that a quad of 6L6GCs,
having had their glass envelopes carefully removed, operate as per spec
when relocated to a bell jar (and thus in a vacuum of calibratable
'hardness' , hint hint hint...)

  Okay, my contribution to off-topicness is done now.


  Cheers

John
Received on Mon Jun 21 2004 - 17:46:12 BST