[time-nuts] tube GPS receivers
alsopb at nc.rr.com
Mon Jun 24 06:58:16 EDT 2013
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
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