[time-nuts] Re: SpectraCom SecureSync1200 Questions

[Bob Camp]

Hi

Each of these modules (GPS or GNSS) speaks its own “language”. Brand T does not talk the same way brand U talks. This may even change between generations. An older brand U may not have quite the same command set a newer brand U device does. Yes, there are basic commands that likely work on multiple devices. This stuff is “on top of that”.

The MCU in the “gizmo” chats with the module to get things going. It then pulls information from the module to see that all is well. Inevitably this gets you into the custom side of communicating with the module. 

Bottom line: You need a module that speaks what the device expects it to speak.

Bob

> On Sep 26, 2024, at 12:04 PM, Robert Krenicki via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I have recently stumbled across a pair of SpectraCom SecureSync 1200 units
> that I have been restoring.  One is a 1200-003 (AC powered, TCXO, GNSS),
> and one is a 1200-233 (AC/DC powered, standard Rubidium, GNSS).
> 
> A touch of backgound: One had a dead CF card, but I was able to clone the
> card from the other unit and updated both to the latest software.  The
> 1200-003 came equipped with a Trimble RES-SMT GG, which works correctly,
> however the 1200-233 came with a Trimble Revolution-T which does detect the
> antenna, but never sees any satellites.  I am obviously more interested in
> using the unit with the Rubidium Oscillator, so I swapped the GNSS modules
> around and the -223 unit is now working.
> 
> On to the questions:
> 1) I am seeing more instability on the Rubidium Oscillator than I
> expected.  I am regularly seeing phase errors of ±100ns.  I have never
> worked with a Rb clock before, but I would expect smaller errors than
> that.  Is this normal?
> 
> 2) I purchased a uBlox M8T GPS module off of eBay, as I know that the more
> recently manufactured units use these and should be supported.  It showed
> up this morning and I replaced the bad Revolution-T, but the system does
> not seem to recognize it at all.  The uBlox module is in the exact same
> form factor and dropped right in, but I do not know if it is incompatible
> or if it is defective.  I am unsure on how to test the unit externally.
> The carrier board says WD22UGRC, and according to a random thread on
> u-blox's forum, it shares the same pinout as the Trimble units.
> 
> 3) I intend to use the -233 unit as my primary timesource in my
> homelab/shack.  I only have AC power connected to it, so it is constantly
> complaining about a lack of DC input.  I have been trying to find a way to
> disable this alarm which also translates to a red light on the front of the
> unit.   Short of hooking up a 48v power supply, is there any way to get
> around this?
> 
> I was hoping that someone amongst this group had some experience with these
> units, or their NetClock 9400 series sister that might be able to shed some
> light on this.  I appreciate any help!
> 
> Rob KB1IPB
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