[NLRS] Fwd: Re: [scarc] "I shall return ..."

[Dr. Gerald N. Johnson]

-------- Original Message --------
Subject: Re: [scarc] "I shall return ..."
Date: Fri, 25 May 2012 16:58:20 -0500
From: Dr. Gerald N. Johnson <geraldj at weather.net>
Reply-To: geraldj at weather.net
To: scarc at iastate.edu

Tubes have not left very high power transmitters yet.

As for receiving and computing, there is more computer power today in a
volume the size of a 6SN7GT than there was in a bushel sized computer a
decade ago, and more computer power in the volume of that tube than all
the world's computers two decades ago all together. Today the package is 
increasingly important to make the hardware big enough for human fingers 
to handle while the contents gets to have a 2 GHz CPU with 100 GB of 
memory in two chip scale packages maybe as big as 1/2" square by 1/16th 
inch thick but probably smaller this week.

Part of the problems with EMP and cosmic particles in solid state is
that the geometry of the parts is the size of those atomic particles
(with new semiconductor using 12 micron geometry next year) so that the
passage of that atomic particle changes stored energy (as most memory is 
based on stored charges) with very low voltage supplies like 1.2 volts 
to keep power consumption down because the capacitive gates take more 
drive power with larger voltage swings to charge in a few picoseconds.

The only way tubes could be competitive would be if the tube geometry
was as small working at similar low voltages, and then it would be as
susceptible to EMP and cosmic particles as semiconductors.

As for electron mobility, there are commercial MMICs made for the 1/2 to 
1 TeraHz region and there never have been tubes made for that frequency 
range. Gallium Arsenide has pretty good electron mobility and when the 
active device is only 20 microns across, it doesn't take long for that 
electron to make the passage.

73, Jerry, K0CQ

On 5/25/2012 1:55 PM, W0WOI at aol.com wrote:
> *Return of the Vacuum Tube *
>
> Vacuum tubes suffered a slow death during the 1950s and '60s thanks to
> the invention of the transistor.specifically, the ability to
> mass-produce transistors by chemically engraving, or etching, pieces of
> silicon. Transistors were smaller, cheaper, and longer lasting. They
> could also be packed into microchips to switch on and off according to
> different, complex inputs, paving the way for smaller, more powerful
> computers.
> But transistors weren't better in all respects. Electrons move more
> slowly in a solid than in a vacuum, which means transistors are
> generally slower than vacuum tubes; as a result, computing isn't as
> quick as it could be. What's more, semiconductors are susceptible to
> strong radiation, which can disrupt the atomic structure of the silicon
> such that the charges no longer move properly. That's a big problem for
> the military and NASA, which need their technology to work in
> radiation-harsh environments such as outer space.
> http://news.sciencemag.org/sciencenow/2012/05/return-of-the-vacuum-tube.html
>
>
>
>
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