[time-nuts] tube GPS receivers

[Brian Alsop]

On 6/24/2013 01:44, Jim Lux wrote:
>
> Lots of rotating drum memory and acoustic delay lines were used back then.


Interesting you should mention this.  One summer job had me working at a 
company that made acoustic delay line memories.  Interesting beasties. 
You stuck the data in at one end . The output was connected back to the 
input to recirculate the data. One wound the magnetic wire in a flat 
rectangular box.   A torsional mode was used rather than push/pull.  A 
maximum of about 50 milliseconds of memory was possible.  A special near 
zero temperature coefficient wire was used as the medium.  One used 
either return to zero or non-return to zero data formats. NRZ logic 
doubled the memory.  Part of the job involved laying out PCB's by hand 
for the electronics.  IC's were just coming on the scene.  RTL logic was 
the only thing available.  For military applications "flat packs" were 
used.  Through hole IC's were used for everybody else. Interesting that 
flat packs disappeared for about 20 years until SMT became the rage.

The company eventually died due to lack of suitable wire and other 
memory advances.

Brian


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