Sorry no idea.
It will however be offset from time if your source encodes rs232 and then
you decode it...
Easy way for everyone with a short wave receiver and scope would be to
measure the tick on 1 channel and if I recall the pulse out or you can also
look for the IRIGB leading data. As I recall its fixed and you can see it as
a pattern
But adding a server and etc I am sure its close to 1 second.
Just did not have a need to get that detailed.
I run gps connected to a pic that drives a home brew irigb gen and that
drives numbers of decoders.
The pic does several things. It extracts the time from gps and then
calculates the proper time to acount for the irigb encoder delay.
Essentially I output the next second ahead of 0 time.
Liked all of this pretty well and did essentially the same trick with a
smpte tc generator using jam sync. Works very well. I jam every 10 minutes
so that its always on time. If power fails I jam as soon as things are
stable within 10 seconds.

On Wed, Nov 25, 2009 at 3:03 PM, SAIDJACK@aol.com wrote:

SAIDJACK@aol.com said:

What sort of accuracy do you want?

You aren't going to get nanosecond accuracy out of a ntp server running over
an ethernet[1].  On the other hand, sub-ms isn't hard with a good OS and/or
good software.

It's fairly easy to get a reasonable sanity check on a (s)ntp server.  Just
setup a known good ntp system and have it monitor the DUT.  The reference
implementation for ntp (http://www.ntp.org/) has lots of support for
collecting data.

The key step in making a PC keep good time is tweaking the clock frequency.
This is the software equivalent of the EFC on an oscillator.  ntpd calls it
drift.  You can use it as a thermometer.

1. There is a group working on that level of accuracy.  It takes special
   hardware that can put a time-stamp on a packet as it leaves or arrives.
   http://en.wikipedia.org/wiki/Precision_Time_Protocol

--
These are my opinions, not necessarily my employer's.  I hate spam.

I don't think the oscillator quality in the typical PC is good enough to ever get nanoseconds, even with tons of tweaks and temperature compensation, etc.  The short term variability/phase noise is too high.

Microseconds, I think you could do.

More than just a casual group.  You can buy IEEE 1588 products from, among others, Symmetricom.

Hi

Doesn't everybody run OCXO's for the clock in their PC?

Bob

On Nov 25, 2009, at 4:41 PM, Lux, Jim (337C) wrote:

paul swed wrote:

Are the PIC and irigb encoder written up any place. I have a couple of
GPS receivers and
an irig display and I would like to connect them. Been meaning to build
an irig encoder myself.

Bill K7NOM

On Wed, 25 Nov 2009, Bob Camp wrote:

you should make one of those text displays on the bottom of your email
that reads:  my PC clock is controlled by an HP10811

That distinguishes Time-Nuts members from the general public.

Hi

Actually it's a double oven (of course that starts to bleed over to another thread). I also have a bunch of boards running with single ovens ...

I know I'm not the only one on the list doing this.

Bob

On Nov 25, 2009, at 8:35 PM, Jeffrey Pawlan wrote:

I thought that was the "Starfleet Academy" or "Vulcan Science Academy"
bumper stickers we have.  ;)

-Bob

On Wed, Nov 25, 2009 at 6:35 PM, Jeffrey Pawlan jpawlan@pawlan.com wrote: