On Tue, 28 Dec 2004 18:37:24 -0800, "Jim Burns"
wrote:

A friend of mine has a 12v Garmin 430 that simply does not pick up the
satellites. It worked fine about 3 weeks ago (the last time he flew) but
now it fails to find any satellite signals. One avionics tech said that it
had "lost it's almanac" and to pull it out and let it sit for a couple hours
and it should pick up the satellites and work fine. No such luck. All
power and antenna connections are good and nothing has happened to the
airplane or the equipment since it flew last. Any ideas? Anybody ever hear
of such a thing?

The almanac includes a list of parameters that allow the GPS receiver
to determine where to 'look' for each satellite.

Without an almanac (and a valid time reference), the GPS receiver is
forced to brute force search for the satellite PRNs. Older GPS
receivers did not have enough processing power to effectively perform
this brute force search. So they would take 15+ (sometimes much
longer) minutes to 'cold start'.

Newer GPSs have more powerful processing engines, and do much better
on cold starts. I do not know for sure, but would expect a 430 to
have a new enough engine to manage a cold start in ~15 minutes. So
anyway, that is a possibility.

If there is an option for setting the time on the receiver, start with
that. Be sure and set the clock as accurately as you can. Make sure
the plane is outdoors and has a good 'view' of the sky. Pulling it
into a tight row of T-hangars still leaves a lot of the horizon
blocked. It is probably best to take it for a flight.

If the plane is flown for 30 minutes and the 430 doesn't lock, there
is a problem, time to troubleshoot. I would pull the radio and have
an avionics shop bench test it. That way you know if you are dealing
with a radio problem or an antenna/cabling issue. (from your
paragraph above, I am wondering how the antenna and connections were
verified 'good' without getting the GPS to work).

-Nathan