[time-nuts] SSR-6t Connector

Ed Palmer ed_palmer at sasktel.net
Fri Dec 21 17:37:27 UTC 2012

Hi Bob,

I agree that the HUP is basically determined by the OCXO, but the GPS is 
the reference that the OCXO is compared to when determining the HUP.  So 
it seems reasonable to ask if a better GPS will improve the HUP numbers.

Even with the flaky receiver, my Z3801A was producing 1 PPS signals with 
a standard deviation of < 300 ps and a max - min range of about 2 ns.  
That was measured over multiple runs of 1000 measurements each.  At 
those levels, you start to wonder whether the GPS is the limiting factor 
or is it the internal architecture and algorithms of the Z3801A itself.


On 12/21/2012 11:12 AM, Bob Camp wrote:
> Hi
> The holdover uncertainty prediction is far more a function of your OCXO than of the GPS.
> Bob
> On Dec 21, 2012, at 12:00 PM, Ed Palmer <ed_palmer at sasktel.net> wrote:
>> Since I have a Z3801A this is an interesting development.  Do you expect to see improved performance or is this simply to replace a dead VP receiver and bring the Z3801A back to life?
>> My 6 channel VP receiver was flaky so I replaced it with an 8 channel model.  My Holdover Uncertainty Prediction is now oscillating between a high of 2 - 3 microseconds and a low of 200 - 300 ns with an oscillation period of 7-9 days.  It's only been running for a few weeks so I'll have to wait and see if the oscillations die out.  Depending on how things settle, there might not be any need (or room) for improvement.
>> Ed
>> On 12/21/2012 10:26 AM, W2GPS wrote:
>>> Tom,
>>> Synergy already has a carrier board to put the SSR-6T receiver into a VP, UT,
>>> UT+, etc. socket. All that is needed is firmware support for the old 8-channel
>>> messages. I am planning to implement this capability for Synergy. It's just a
>>> matter of time and priorities. Eventually Synergy will have the solution for
>>> this problem. If you could gather a list of Time-Nuts people who would like one
>>> or more of these and send it to Art that could speed the process along.
>>> Rick
>>> -----Original Message-----
>>> From: Tom Van Baak [mailto:tvb at LeapSecond.com]
>>> Sent: Friday, December 21, 2012 11:15 AM
>>> To: Discussion of precise time and frequency measurement
>>> Subject: Re: [time-nuts] SSR-6t Connector
>>> Hi Paul,
>>> I'm pretty sure the hp Z3801A and 58503A/B (and perhaps other 1990's era) GPSDO
>>> use the Motorola Oncore VP receiver. It was, and still is, a famous GPS timing
>>> receiver. Later, many GPSDO evolved to use the Motorola/iLotus M12 receiver.
>>> The new Synergy SST-6T is a clever combination h/w and s/w that turns a uBlox 6T
>>> & PIC into a PCB that is both h/w and s/w compatible with an M12. It's a drop-in
>>> replacement. But as such, it won't work in a device that is uses an old Motorola
>>> UT/GT/VP receiver.
>>> I suggested that they also come up with a board that is VP compatible, but you
>>> realize the number of 15-year-old Oncore VP's in the field is probably not that
>>> high. It would make an excellent labor-of-love project to create a VP-compatible
>>> uBlox 6T board, but it's probably not something you can make a business case
>>> for.
>>> /tvb

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