On 06/22/2013 11:10 PM, Hal Murray wrote:
[email protected] said:
On 06/22/2013 05:27 PM, Didier Juges wrote:
A real treat would be to do the GPS receiver with tubes ;)
The the correlation channel(s) would be possible to do in tubes. The rest of
the processing is "problematic".
The IBM 709 was tubes. (Well, mostly, they used transistors on the front end
of the memory.) Memory was 32K 36 bit words. Call it 128K bytes. That
might be enough.
It had a cycle time of 12 microseconds. 12 ns would be 1000x as fast.
That's 80 MHz, a reasonable speed for an ARM. So the CPU in today's GPS
systems is 300x to 1000x faster than the 709.
Anybody know what fraction of an ARM it takes to do the GPS calculations?
Do you have to keep up, or can you do the calculations for every N-th second?
I have articles desribing how they looked at the feasability of using
RCA 1802 and 6502 as processors. Some of the early 2-channels receivers
used a pair of similar 8-bitters if I recall correctly. You don't need
much, but it's still a fair bit more tubes than just the bandpass
processing would require which is mostly shift-registers, counters and
some integrators.
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
