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[aprssig] balloon tracker

Curt, WE7U archer at eskimo.com
Wed Mar 2 21:24:11 UTC 2005

On Wed, 2 Mar 2005, Scott Miller wrote:

> I think some people have reported GPS receivers freezing up, too.
> I'm sure some folks here could tell you more about packaging them
> to keep them warm.

As I recall most of the GPS'es have a temp sensor in them.  I can
get a readout for the internal temp on my GPS-II+ by throwing it
into a special mode.  They have that sensor in order to avoid having
a crystal oven.  The GPS self-calibrates for temperature, but has to
be baked/frozen through it's normal ranges in order to gain it's
data for this calibration.  They do this at manufacture.

I'm not sure what the extremes are that they cook/freeze a GPS to,
but I suspect you're going outside those ranges, in which case the
GPS might not know where it's oscillator is sitting, therefore might
not be able to find the satellite signals anymore.  I think most of
them will auto-calibrate in this case, but it takes a long time.  If
they've never hit those temperatures before and you have a spinning
payload or other sky-view problems, they might lose lock and not
regain it until they get back within their normal temp range.

Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
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