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

[GandalfG8 at aol.com]

Hi David
 
Aside from in the Jupiter itself the Zodiac chipset was widely used in GPS  
navigational receivers and, just for example there's one that's  possibly 
similar to yours, albeit marked ZOD1, shown here....
 
http://www.gpsnuts.com/mygps/gps/hardware%20reviews/randmcnally/rand_mcnally
_gps.htm
 
I assume you're aware that although the 1PPS and 10KHz were themselves  
locked together in most, and possibly all, versions of the Jupiter, in the  
earlier versions, at least up until firmware 1.03, these weren't in sync with  
UTC.
Later versions, 1.50 for example, were in sync but other "settling  down" 
issues have resulted in version 1.80 being generally accepted as the  earlist 
"fully stable" release.
 
However, in this instance I suspect what you've got is far enough  removed 
from a Jupiter that the firmware is different and that 1.83 firmware  
version number is probably just an unfortunate coincidence.
What you're seeing exactly describes the situation in the earlier Jupiters  
so it would seem likely that 1 PPS and  10KHz just aren't synchronised to 
UTC in these either.
 
Regards
 
Nigel
GM8PZR
 
 
In a message dated 28/07/2013 00:23:42 GMT Daylight Time,  
david at smithfamily.net.au writes:

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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