[time-nuts] A milestone approaches

[Bill Hawkins]

Got this from a friend whose MN license plate is UNIX.

Begin copy of note

I'm curious if your friends on the time wizards mailing list have
noticed that an important moment in computer history approaches.

On Thursday night, 21:40 PM CST, it will be exactly 1.5 billion seconds
since Jan 1, 1970 UT, the Unix EPOCH.  At that instant, billions of
Linux and Unix computers and devices, everywhere on the planet, will all
return time() == 15.  It will not be until 2033 when that number
reaches 2 Billion.  The Thursday date is computed as follows:

% cat >epoch.c
#include 
#include 
#include 

int main(int argc, char **argv) {
const time_t gsec = 1.5e9;
struct tm thursday = *localtime();
char buf[100];

strftime(buf, sizeof(buf), "%m/%d/%y %H:%M:%S", );
printf("Epoch + 1.5B seconds = %s\n", buf);
return 0;
}
% gcc -Wall epoch.c
% ./a.out
Epoch + 1.5B seconds = 07/13/17 21:40:00
%

And if they haven't noticed, it might be a good time to point it out.

End copy of note

Some of us are impressed by long strings of zeros, so here I am,
pointing it out.

Bill Hawkins

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Re: [time-nuts] GPS Units in Z3801A

[Bob kb8tq]

Hi

I’ve swapped out the GPS on a couple of them. Not 100% sure what went wrong. 
Swapping out a cheap GPS was a pretty easy decision compared to trying to 
board level troubleshoot an undocumented GPS. When the swap out fixed the 
problem,
I moved on. 

Bob

> On Jul 11, 2017, at 6:27 PM, Hal Murray  wrote:
> 
> 
> I have a Z3801A that has lost contact with GPS.  The GPS module is working - 
> the list of not-tracking  satellites changes occasionally, but it never 
> tracks anything.  I've tried swapping antennas and such but that hasn't 
> helped.
> 
> How often does the front end of the GPS module die?
> 
> Will the newer 8 channel modules work in the Z3801A or do I need to locate an 
> old 6 channel version?
> 
> Is there a tells-all web page or message to this list about GPS modules for 
> the Z3801A?  I'd expect one, but I haven't found it.
> 
> 
> 
> I noticed that the UTC time from the status page is different from the T2 
> time.
> 
> T220170719039300141
> 
> The UTC clock seems to have gone crazy.  From the status page:
> Tracking: 0Not Tracking: 6UTC  06:28:15 [?] 01 Nov 
> 2018
> Tracking: 0Not Tracking: 6UTC  06:28:15 [?] 22 Aug 
> 2019
> Tracking: 0Not Tracking: 6UTC  06:28:15 [?] 19 Dec 
> 2019
> 
> The T2 time is a day old.  My guess is that it pulled the time it's using for 
> T2 from wherever it stores the log slots.
> 
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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[time-nuts] GPS Units in Z3801A

[Hal Murray]

I have a Z3801A that has lost contact with GPS.  The GPS module is working - 
the list of not-tracking  satellites changes occasionally, but it never 
tracks anything.  I've tried swapping antennas and such but that hasn't 
helped.

How often does the front end of the GPS module die?

Will the newer 8 channel modules work in the Z3801A or do I need to locate an 
old 6 channel version?

Is there a tells-all web page or message to this list about GPS modules for 
the Z3801A?  I'd expect one, but I haven't found it.



I noticed that the UTC time from the status page is different from the T2 
time.

T220170719039300141

The UTC clock seems to have gone crazy.  From the status page:
Tracking: 0Not Tracking: 6UTC  06:28:15 [?] 01 Nov 
2018
Tracking: 0Not Tracking: 6UTC  06:28:15 [?] 22 Aug 
2019
Tracking: 0Not Tracking: 6UTC  06:28:15 [?] 19 Dec 
2019

The T2 time is a day old.  My guess is that it pulled the time it's using for 
T2 from wherever it stores the log slots.




-- 
These are my opinions.  I hate spam.



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[time-nuts] J06 HP-59992A time interval calibrator for HP-531xx counters

[Mark Sims]

I did a (rather crude - breadboard) experiment of using an analog vs XOR freq 
doubler driving a flip flop.  I did not see much difference between the $0.10 
XOR doubler vs the $6 analog doubler.

Two $0.10 2P4T PCB mount slide switches would replace the relays.   The total 
parts cost for the device looks like less than $10 plus the PCB cost...  which 
for 50 pieces of a 3x3" four layer board would be around $3 each.
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Re: [time-nuts] J06 HP-59992A time interval calibrator for HP-531xx counters

[Orin Eman]

FWIW Re: the relays.  I worked through the Omron discontinuation notices
for the first relay (I figure the original was a G5Y series, not GSY as in
the manual) and it looks like the G6K series, easily available at Mouser
and about $4 each would work, though you'd have to use a DPDT.

The other two relays are cute little TO5 relays from Teledyne - 412 or 712
series, 12V coil.  The 712-12 will cost $35 at Mouser.  Ouch.

>From reading the paper and the Basic program, the _critical_ part of the
circuit is getting the delays with the outputs swapped exactly the same as
the delays with the outputs unswapped.  A non-trivial task since the traces
are all 50 ohm stripline.  (Or so the manual says - a picture of both sides
of the original PCB would help immensely in determining how critical the
layout is.)

(Phase differences due to the splitters are eliminated by taking a reading
with the outputs unswapped, then with the outputs swapped.  Taking half the
sum of these two readings eliminates the phase error due to the splitter.
At least that's what the Basic program does; the description in the paper
is slightly different, but the equation simplifies to the same thing.)
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