[time-nuts] Rockwell/Conexant Jupiter(?) 10kHz Output Off Frequency

David Smith david at smithfamily.net.au
Sat Jul 27 19:23:15 EDT 2013


The Jupiter (TU-30) board in my homebrew GPSDO has died.

A friend gave me some unmarked Jupiter-like boards with Conexant chips 
that he had been told were Jupiter compatible.
The boards are mounted on an aluminium plate that has a puck-type 
antenna on it.  One of the chips has a sticker with ZOD8 V1.83 printed 
on it.

The boards have the same connections as a Jupiter, and I've been able to 
connect one to my GPSDO in place of the dead Jupiter.
It eventually starts outputting sensible messages with location etc. and 
the homemade display on the GPSDO shows that everything is supposedly 
normal.

However, the PLL will not lock.  Even though there's 10 kHz from the 
board (which I can only measure to 1 Hz accuracy), the PLL keeps hunting 
for lock.
The 10kHz is in sync with the 1pps also from the board.  However, when I 
compare the 10kHz to 10 MHz from another GPSDO, it doesn't appear synced 
to GPS - it must only be fractions of a Hz off, though.

At the moment, I'm thinking there are 3 possibilities:
- I need to send a command to the board to configure the 10kHz/1pps 
somehow.  The Jupiter doco doesn't show any command like that and seems 
to assume the 10kHz and 1pps are always there.
- There are components for the 10kHz/1pps syncing missing.  I've already 
had to add a jumper wire where bits for supplying active antenna power 
were missing (from factory).
- The firmware doesn't support 1pps / 10kHz.  Perhaps the boards were 
meant for navigation only.

Does anyone recognise these boards and have experience with extracting 
10kHz from them?

Regards,
David Smith



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