[aprssig] GPS Epoch Rollover Findings

[KF4LVZ]

On 2019-04-26 09:20, Greg D wrote:
> No joy here.  Garmin eTrex Vista HCx.  I found the apparently latest
> firmware, 2.30, and updated to that.  Also there was a prior
> date-related patch of some sort
> (https://www8.garmin.com/support/download_details.jsp?id=3731).  Tried
> that. 
> 
> Let it run overnight.  No luck.  How long did it take for the Almanac to
> update? 
> 

The constellation transmits the almanac in pieces over a period of about
12 minutes.  It can take longer to build up the almanac if any
particular transmission frame was corrupted.  This is why most GPS
manuals specify that a cold boot can last up to 30 minutes or more, more
opportunities to capture the full almanac.