Okay that makes some sense. I will have to ponder over this and see how it
will help. But in any case (which I sort of expected) it's a time consuming
procedure, during which the counter isn't available for other use. And when I
go to bed I won't know the next day if I might have missed a count.
This business of precise time is amazingly interesting, especially since an
amateur like me can make some pretty impressive calibrations.
The OCXO in the 5328A runs 24/7 but I don't know if it drifts more when the
counter is on than it does with the counter off (due perhaps to internal
temperature changes). Of course, any drift while the counter is off is not
important.
Luckily I can often receive 25 MHz WWV so that is handy for calibration. I
also have an 8657B with its OCXO although that one isn't running with the unit
switched off. (The oven is holding temp 24/7).
All advice here eagerly sought and appreciated.
On a side note, when I measure the 8657B with the 5328A at 700 MHz it's off by
just a few Hz, and stabilizes after a half hour or so. It's the generator that
needs to stabilize, not the counter. I am still unsure which unit is closer to
being correct but I suspect the counter is closer.
Bob
On Wednesday, July 1, 2015 3:36 PM, Bob Albert <[email protected]> wrote:
So I can measure the time interval, which should be one second. If I measure
10 intervals, my resolution would be 1 part in 10 million. I think I can set
the master oscillator closer than that with beating against WWV. So maybe
buying a 1 pps source won't improve anything for me.
On Wednesday, July 1, 2015 2:39 PM, Hal Murray <[email protected]>
wrote:
[email protected] said:
> My linux boxes also did a double 59:
> Wed Jul 1 00:59:58 BST 2015
> Wed Jul 1 00:59:59 BST 2015
> Wed Jul 1 00:59:59 BST 2015
> Wed Jul 1 01:00:00 BST 2015
> Wed Jul 1 01:00:01 BST 2015
That's to be expected (unless you have fancy software).
Internally, Linux (and most other modern OSes) use UTC. The API doesn't
include the TAI offset. There is no way to talk about the extra second.
The same problem happens with the switch to summer time. You need the
time-zone to tell if the time within the magic extra hour is summer time or
winter time. Without the zone, you have to pick one and then there is no way
to talk about the other one.
To insert the extra second, Linux just sets the time back 1 second, the same
way you set your clocks and watches back in the fall.
--
These are my opinions. I hate spam.
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