bg at lysator.liu.se
Wed Aug 3 16:55:56 EDT 2005
Tom Clark <w3iwi at toad.net> writes:
> Rick Putz asked
> To All,
> Has anyone done any studies on the Nav Man Jupiter T and Pico T series receiver
> s? They use the SiRF chip set and provide a 10 Khz output that is said to be co
> herent with the 1PPS.
> Just curious.
> I did a lot of testing on the Jupiter-T that has an ONCORE VP physical
> footprint and MOT compatible command set.
I have used a normal Jupiter for - less demanding - timing as a
refclock for NTP.
> First of all, it is NOT the SiRF chipset.
Not in the older Jupiter T, but the newer Pico, I think are SiRF.
> As I understand it,
> Collins/Rockwell sold their semiconductor operation lock, stock &
> silicon to the C/R spinoff Connexant, and it was Connexant that built
> the Jupiter-T with C/R parts and knowledge. Then Connexant's GPS was
> sold to SiRF, except that the Jupiter C/R series was sold to NavMan in
> New Zealand.
The NavMan Jupiter recievers get their chipsets from SiRF. If the
chipsets are related to the legacy Rockwell/Connexant line, I do not
know. It could be normal SiRF, but with firmware emulating the Jupiter
binary command set.
> So, under the assumption that the Jupiter-T you mention is the ONCORE
> footprint that I tested, here are a few answers.
They have had several generations of -T receivers as variations on
their standard receivers Jupiter, Jupiter 11, Jupiter 12, Jupiter Pico
For NTP use - at least the old one I have - is useless in
NMEA-mode. The serial string lags its PPS-pulse either 1+ second or 2+
seconds depending on internal workload in the processor. However in
Jupiter/Navman binary mode it performs quite fine.
PS The one _or_ two second delay apparently did bite some timetagging
device used by astronomers. Older manuals and information is available
from http://www.gpskit.nl DS
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