[time-nuts] Help needed: Jupiter-T TU60-D120

[Lasse]

Richard,
I think I finally have figured out how this GPS-receiver do operate 
(with some hand-holding from James Miller).

At power-on it will transmit "ff 81 9c 04 01 00 00 00 64 79 00 00 00 00" 
and then wait for command.
This erronously led me to think it would be in Navman binary mode, 
*Wrong* !
It only listens for a subset of Motorola binary commands, despite the 
previously transmitted string.
Secondly, it seems best to let the receiver have a few seconds of 
start-up before sending commands, or it seems to go deaf.

Once I had this figured out, it is simple to change to Navman binary 
with the @@Wb command if that's what you want. One thing is that
Labmon and WinLabmon seems outdated as several of the commands are 
unrecognized.

Finally, the receiver do retain settings for a few minutes (hours?) even 
with-out the back-up capacitor, so a quick power-loss will not mean that 
the GPS is back to factory reset.
Letting is be off for several hours WILL turn int into factor reset state.

Hopefully my findings will help others struggling to get their TU60-D120 
going.

Now a "simple" question... I intend to turn this into a GPSDO, using the 
scheme of James Miller, but would like to have some indication on the 
status of the system. By setting the @@En command I should be able to 
have no 1PPS as long as there are no satellites tracked. If the GPS 
acheive lock, it should then turn on 1PPS, flashing LED would be a neat 
indicator. Now this should be farily easy by sending a few commands at 
start-up using a microcontroller. The question is would it be beneficial 
to set the receiver to HOLD POSITION and turn on the T-RAIM function? 
Would this affect the stability of the 10kHz/1PPS signal?? It seems the 
GPS has these functions turned off as default.

Comments are most welcome!

/Lasse SM5GLC