[time-nuts] HP Z3805A GPS replacement ?

[Gregory Beat]

HP Z3805A Time & Frequency GPS Receiver
by Brooke Clarke
https://www.prc68.com/I/Z3805A.html#OHPGPS

Tim -
Later models of the HP/Symmetricom GPS Time & Frequency models used the Motorola Oncore 8-channel GPS receivers (VP or UT+ models).  Those 8-channel receivers have same form factor and command responses (Motorola binary, plug-n-play).
No firmware upgrades were released by HP or Symmetricom to support later internal GPS receivers.  Microsemi/Microchip provides no additional support.
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Motorola / i-Lotus 12-channel GPS receivers have a smaller form factor (adapter board required) and expanded/enhanced command responses (Motorola binary).
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Art Sepin, at Synergy Systems, has been a long-time support of TAPR and time-nuts projects over the past two decades (starting with Tom Clark’s TAC-2 kit).
Feel free to contact him, to consider options.

Synergy offers a 10% discount to time-nuts, TAPR, and amateur radio experimenters.
He has various solutions, based on “what you desire” (multi-GNSS, adapter board for M12 receiver, etc.).
https://synergy-gps.com/products/gps/timing-boards-modules/
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I researched these options, before acquiring a Symmetricom 38305B receiver last month.  However, that unit was pristine (~2000 hour operation), used an 8-channel receiver, and did not require any changes (it worked, after proper date setup).

Your Decision, to make.
https://www.prc68.com/I/MOTGPS.html

A.) Operate with the Oncore PVT 6-channel receiver.  Use a good outdoor GPS antenna.

B.) Acquire a used (surplus), UT+ 8-channel receiver, and swap out for your current Oncore PVT 6-channel receiver.  These used receivers will likely be date inaccurate (1024 week rollover).  The Motorola Part numbers determine various options: Antenna connector orientation (straight, right angle), backup battery, etc.

C.) Acquire a newer GPS receiver (M12+ or Ublox), with Adapter board and programmable capabilities to “Emulate” the original Oncore 8-channel command set.  
The Synergy SSR-6T may be a receiver to consider for upgrade.
https://synergy-gps.com/wp-content/uploads/2018/11/SSR-6T-TN-493-E-053019.pdf

D.) As noted on time-nuts and EEVBlog, the 1024 rollover issue with older GPS receivers can be resolved with these HP/Symmetricom 38xxx time/frequency receivers by entering specific Setup commands (SCPI commands), BEFORE the GPS Antenna is attached.

E.) Mark Sims has Lady Heather correct the 1024 week rollover issue for its display.
However, that doesn’t change the Data stream from the GPS receiver.

Good Luck!

greg, w9gb
chicago

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Date: Tue, 15 Oct 2019 16:25:21 +1100
From: Tim Tuck
To: Discussion of precise time and frequency (time-nuts)
Subject: [time-nuts] HP Z3805A GPS replacement ?

Hi all,

I've been gifted an old HP Z3805A GPSDO. It took quite some time to get its head together since it hasn't been switched on in years.
I see talk about changing out the 6 channel Motorola GPS for something else. Suggestions point to the Motorola M12 ONCORE, but I've not found any detail from anyone anywhere that has done this.

So...
1.) Can I replace the GPS with an ONCORE M12 ?  Has anyone done this ?
2.) Are there any "gotcha's" I need to be aware of ?

Thanks,
Tim