[time-nuts] HP Z3801A, GPS vs UTC?, NTP

Ron Hahn (EI2JP) ei2jp at dhco.org
Sat Jun 11 14:12:02 UTC 2011

On 6/11/2011 2:47 PM, Magnus Danielson wrote:
> On 06/11/2011 02:11 PM, Ron Hahn (EI2JP) wrote:
>> On 6/7/2011 10:40 PM, cook michael wrote:
>>> Le 07/06/2011 21:15, rtm at lcs.mit.edu a écrit :
>>>> I have an HP 58503A. It has an "Option H14,H19" sticker on the
>>>> back. The
>>>> circuit board has "58503-60001 Rev C" stamped on it. It has been
>>>> running
>>>> continuously and locked to GPS for a few days, and it knows the
>>>> correct
>>>> number of seconds between GPS and UTC.
>>>> The unit displays GPS time, without the leap seconds correction. The
>>>> front-panel display says "GPS xx:yy:zz", and ":system:status?" says
>>>> "GPS
>>>> 1PPS Synchronized to GPS Time", not "to UTC" as the manual shows.
>>>> I'd be much obliged if anyone could tell me how to get the unit
>>>> to display UTC instead of GPS time.
>>> I think these use a similar command set to the Z3801A
>>> try
>>> :diag:gps:utc?                    should show 0 if the unit is in GPS,
>>> 1 if UTC
>>> if that gives coherent results, try
>>> :diag:gps:utc 1
>>> to force the mode
>> Colleagues,
>> For someone who is not understanding these modes, can you explain what
>> is this difference between UTC and GPS time?  I have a HP Z3801A which I
>> have been using for some years.  Do I need to change this to UTC time?
> If you only wish a 10 MHz and PPS, no. GPS time will do just as well.
> If you also want UTC time for NTP server for instance, then you do
> want either to use the UTC mode or let the server know it runs on GPS
> time and compensate itself.

I am interested in UTC time for weather satellite reception,
synchronising via NTP.  I tried the GPSCON program for the Z3801A but
could never get it to broadcast ntp information on my LAN.  Recently, I
have purchased some Sure GPS boards from Sure Electronics
(http://www.sureelectronics.net/goods.php?id=99).  David Taylor has a
great page on this at http://satsignal.eu/ntp/Sure-GPS.htm ... but now I
am thinking his time is maybe always 15 seconds off, yes??


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