[time-nuts] tube GPS receivers

[Chris Albertson]

Magnetic cores were not invented until the 1950's and realy cam into use as
tubes were beibg replaced by SS.  But there isnot reason yu can't build a
tube computer with core memory.   I have actually seen and used a computer
that had one megabyte of core memory.  The stuff was still in use in the
late 1970s   1MB was a lot of RAM in 1975.

You can have very good reliability with tube circuits.  It was just that
few people wanted to pay for it.  Down time was cheaper.  It is not hard to
add redundancy to a circuit but it does have a huge cost multiplier effect.
4x or 5x the price.   One simple way is to use 3 or 4 tubes with their
output tied to a resistive adder.  If one tube fails the result (because it
is binary) is still the same.   With computers no one would pay for fault
tolerant design until it was reasonably affordable.   Even today we mainly
just put up with failure except for airplane controllers, huge web sites
like Amazon and the like.


On Sun, Jun 23, 2013 at 9:53 AM, Brian Alsop <alsopb at nc.rr.com> wrote:

> On 6/23/2013 14:40, Bob Camp wrote:
>
>> Hi
>>
>> AC137 doesn't ring any bells. True tube core (no solid state at all)
>> isn't something that was dimensioned in K words. A couple hundred words was
>> pretty big stuff. "Quite a bit" of core done that way is a lot of tubes. As
>> the number of tubes goes up, the time to failure comes down….. hours …
>> minutes … who knows.
>>
>> Bob
>>
>>
> Yeah, it gets to be like the cross country aircraft races in the 20's. The
> mechanic had to fly with the pilot. (The MTBF of many of the engines used
> was measured in hours.) If necessary he had to climb out on the cowling
> while in flight to change plugs and fix whatever possible without landing.
>  What would OSHA say about that?
>
> Needless to say future generations will probably find lots of aircraft
> spark plug artifacts in their digs.
>
> Brian/K3KO
>
>
>
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-- 

Chris Albertson
Redondo Beach, California