[time-nuts] Re: Drop-in replacement receiver boards for Z3801A

[Gregory Beat]

The Synergy SSR-series UT+/VP Single Board Replcement 
https://synergy-gps.com/synergy-products/ssr-series-ut-vp-single-board-replacement/
does have a modern u-processor with ability to upgrade its firmware (future-proof).

The Synergy SSR board converts Ublox GPS receiver’s native protocol to that of the obsolete Motorola Oncore VP/UT+ receivers.  Since modern Ublox receivers detect and receiver more than 8 or 12 satellite, the u-processor (MCU) can select the “Best” 8 or 12 GPS satellites to send to GPSDO (in Oncore format). The form factor and 10-pin (2x5) header connection is identical to the late 1990s Motorola Oncore receivers.

WHY BUY or UPGRADE ?
* Revive from junk pile (dumpster) that GPSDO with a Dead Oncore receiver.
* Modern sensitive receiver (ublox), better ADEV observed and graphed
* Faster GPS Lock, “Best of N” sats passed to GPSDO.
* Fix the annoying Week Number Roll Over (WNRO) issue.
* Future Proofing with ability to upgrade u-processor firmware.
—
Symmetricom 58503B
In 2017, I acquired this late GPSDO model that was “thrown in a closet” from a former ‘Mom & Pop’ cellular company. It had less than 1,000 hours of operation and WNRO may have been mistaken for broken.  This 58503B used the Oncore M12+ GPS receiver with a Goshay Group (Norridge, CA) Adapter board (Form factor, command changes).
—
I started talking to Art Sepin at Synergy about this specific 58503B configuration in 2022.  As Art noted earlier, I sent my 58503B to his experienced software team for full testing.  This testing involved both the UT+/VP receiver replacement (solution I’m using) as well as M12+ receiver replacement with my Goshay adapter board.

Since this was one of the last production runs of the 58503B, a few additional commands (Bob’s fiddly problems) were detected between the Symmetricom’s firmware & the GPS receiver.  These were addressed in the latest firmware.

As Bob noted, this was not an easy task. However, after 2 years of work, I believe a good solution now exists for Oncore replacement.  I tested it with Lady Heather, SatStat, and SCPI commands.

greg, w9gb
chicago
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Date: Tue, 30 Jan 2024 09:58:43 -0500
From: Bob Camp <kb8tq at n1k.org>
Subject: [time-nuts] Re: Drop-in replacement receiver boards for Z3801A
To: <time-nuts at lists.febo.com>

Hi

Just a random comment …..

The Ublox series parts speak a *very* different language than the old Motorola parts. Dropping a stock version of one chip in place of the other isn’t going to work. You either need a custom version of the base chip or some sort of MCU on the board to translate languages. Either way, there’s a whole lot of hard work (and testing) that needs to be done to make that work right. There are a number of fiddly problems you get into. Not at all an easy task. 

Bob