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

jmfranke jmfranke at cox.net
Sat Jun 11 12:45:56 UTC 2011


GPS time differs from UTC by the number of leap seconds accumulated since 
the start of GPS time. Reseting the GPS clocks each time a leap second 
occurs would upset the code generators. The satellites stay in GPS time but 
do transmit the difference between UTC and GPS time to allow receivers to 
make the conversion. If your time display is in sync with the seconds time 
signal from WWV or CHU, your system is set to display UTC. GPS time is 
currently ahead of UTC by 15 seconds. Each time a leap second is added, UTC 
falls one more second behind GPS time. If a leap second is subtracted, UTC 
will move closer to GPS time.
See: http://leapsecond.com/java/gpsclock.htm

John  WA4WDL

--------------------------------------------------
From: "Ron Hahn (EI2JP)" <ei2jp at dhco.org>
Sent: Saturday, June 11, 2011 8:11 AM
To: <time-nuts at febo.com>
Subject: [time-nuts] HP Z3801A, GPS vs UTC?

> 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?
>
> Thanks,
>
> Ron
>
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