[time-nuts] Oooold GPS receiver discussions Austron 2201 as an xample

paul swed paulswedb at gmail.com
Tue Nov 10 14:58:35 EST 2015


There is a good discussion about old GPS receivers that have been running.
Its the NAVSTAR proteus thread.
Very good details in that thread about some issues. Such as the 1024 week
rollover and that the receiver should still keep working. Though the date
and time would be wrong.
Given that theory I fired up the 2201. This is the unit that had no down
converter and I home brewed one using another GPS receiver. Put simply it
all worked.

But its always been a bit magical. Wait for a full moon, jump 3 times
counter clockwise...
Never made sense as to why it worked or really controlling it consistently.
(Why even care for this pain in the ....? Because it has a really good
frequency offset measuring system.)
Over time its become more difficult to get it to work even though the down
converter is having no problem acquiring and locking to satellites.

I think and its a theory its because its looking for SVNs but with the
wrong PRN. (these would be retired SVN/PRN sequences)The trigger was
looking at the satellite it wanted and realizing the PRN was not accurate
and the satellite wasn't even up.
I need to do some more digging but perhaps over time there are fewer and
fewer correct PRNs that align to the SVN.
Does this make any sense at all?

There seems to be no way to tell the system that SVN X = PRN Y

The only other fake out approach as a test will be to find a PRN thats up
and see if that aligns to a SVN.
Then manually enter that SVN as a search.
Regards
Paul
WB8TSL


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