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

[jmfranke]

The former.

John  WA4WDL

--------------------------------------------------
From: "J. L. Trantham" <jltran at att.net>
Sent: Saturday, June 11, 2011 4:16 PM
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts at febo.com>
Subject: Re: [time-nuts] HP Z3801A, GPS vs UTC?

> I have been wondering about this.
>
> Since leap seconds accumulate from time to time, there must be a
> 'difference' between GPS and UTC.  Is the difference related to the 
> rotation
> of the earth around it's axis and around the sun and thus the need to add 
> a
> second or so from time to time as we do with leap year or is there a
> difference in the reference oscillator frequency between the two that 
> allows
> a 'drift' of a second or so from time to time?  I suspect the former.
>
> Joe
>
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Magnus Danielson
> Sent: Saturday, June 11, 2011 8:47 AM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] HP Z3801A, GPS vs UTC?
>
>
> 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.
>
> Cheers,
> Magnus
>
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