GC-1000 Most Accurate Clock Questions

[Don Peterson]

Hi Tim

Actually it's the 3.6MHz output that makes the GC-1000 so desirable.  You can
currently buy any one of a hundred "Atomic Clock's" for around $20.00 - $50.00.
 These clocks all have a local oscillator that just runs freely.  The clock
updates itself regularly so the displayed time is accurate.

He Heathkit GC-1000, however, has a self-correcting local osciallator.  Heathkit
claims that the local oscilllator will have a better than 1 ppm accuracy if
left on over an (undefined) period of time, so that the local oscillator can
be updated multiple times.  This makes a nice frequency standard for many other
possibilities.

When Heathkit originally designed this clock, WWV had not included the date
format function into the WWV signal.  So the date needs to be manually accounted
for with dip switches.  1998 happens to be the largest year that the clock can
display.

Taking all of that into account with the fact that the MK-3870 is no longer
available, we have been considering re-designing another CMOS "single-chipper"
to replace the MK-3870 in the GC-1000.  We have successfully done this in the
Heathkit ID-4001 weather station and despite the fact that the code was stuck
in "beta" for longer than we anticipated, we have done well in sales.

Among the additions planned for the new chip, is the addition of decoding for
the date as well as the time.  Other anticipated features would be storing the
oscillator "trim" value in EEPROM, so the correct value can be arrived at much
faster when power is lost.  Also CMOS operation of the CPU will reduce the over
all power consumption of the clock possibly allowing true battery back-up operation
with the displays blanked.  This however may require some hardware mod's, so
we're not sure yet.

If you'd like to see what's been done on the ID-4001, take a look at:

http://www.d8apro.com/ID-4001.htm

Thanks
Don

>Hi all,
>Been playing with my clock for a few days now after I finally uncovered it

>from a stack of moving boxes.
>I have been running it for the better of 15 years from 12V DC which keeps it

>cool I am sure if kept it on AC it would have slowly cooked to death from a

>bad power supply design.  Always accurate and now the LED's are getting
>retro. I figure in a few years it might even look good enough for the rest

>of the house.
>It has some very quirky features however with the serial port such as the
>clock year does not go past 1998 and time is off by one sec.
>
>See for yourself! telnet to 65.96.182.71 port 2080
>
>So the question is has anyone made any progress on upgrading the RS-232C
>microprocessor U401 heath part 444-200 to go past 1998? A PIC might do it
>but I do not have the expertise
>
>Also can anyone determine the accuracy of the 3.6Mhz standard? I see 0's on

>my counter but some of you I am sure have better counters
>
>Have fun I am happy to be able to "share" my clock finally with others.
>
>Regards
>Tim C
>W1TCC
>Boston MA
>
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