LF: Re: Motorola GPS Time Oddity

["Dave Brown" <tractorb@ihug.co.nz>]

Andy
What happens if you talk to in in binary? Same results?
NMEA seems to often be almost an afterthought in some receivers and 
often odd things happen when using it...
DaveB, NZ

----- Original Message ----- 
From: "Andy Talbot" <andy.g4jnt@googlemail.com>
To: <ukmicrowaves@yahoogroups.com>; <rsgb_lf_group@blacksheep.org>; 
<uk_beacons@yahoogroups.com>
Sent: Saturday, April 03, 2010 5:13 AM
Subject: LF: Motorola GPS Time Oddity


> I've noticed a curious odditity on a Motorola M12 GPS module, when 
> started
> up completely from cold with no stored almanac data:  When the
> module eventually 'appears'  to lock up and show the correct lat 
> /long and
> the NMEA data showing satellite staus 'Valid', the NMEA reported 
> time is 15
> (ish) seconds out.   Which means it hasn't downloaded the 
> leap-second
> correction yet and is still working on GPS time - the NMEA report 
> gets
> corrected after a minute or two longer wait.
>
> BUT... Why does it decide that it has enough info for location 
> calculation
> when it clearly hasn't yet downloaded all the almanac data ?
> It's lying.    Has anyone met this?
> Only the M12 behaves like this out of those tested.  All other 
> modules I've
> used, including the older Motorola. Oncore,. give the correct time
> immediately they show lock.   Of course, if the internal battery is 
> alive
> the almanac data is already stored and it jumps into life 
> immediately with a
> warm start, but after several months of storage - sometimes just 
> weeks -
> this battery goes flat.
>
> Andy
> www.g4jnt.com