[aprssig] Com port SHARING vs Com Port JOINING

[Scott Miller]

For Garmin receivers, at least, my experience is that in NMEA mode they 
output UTC.  In Garmin mode they give GPS time and an offset (about 14 
seconds, last I checked.)

Scott
N1VG

Claude Head III wrote:
> The utility I found for setting the PC's clock is NMEATime. I had known 
> that the GPS system does not correct for leap seconds, but was not 
> actually thinking about that when I first tried NMEATime. Just now went 
> out to the car to check that point.
> 
> I deliberately set the computer's time to several hours, minutes, and 
> seconds in error, then used NMEATime to set the clock. I had a WWV 
> receiver with me , and thus was able to compare the GPS/computer time 
> with WWV @ 10.000 MHz. NMEATime got the time right to within less than 
> about 0.5 seconds. Certainly not the 13 or 14 seconds offset that was 
> mentioned. NMEATime has its own time display, and natively it shows the 
> time as UTC. I guess it is using the computer's internal settings to put 
> the local time in the correct time zone, which is displayed by the 
> computer.
> 
> Come to think of it, I'm not sure whether the correction from "GPS" time 
> to UTC is done inside the Garmin receiver, or by NMEATime. Guess it 
> doesn't really matter. When it gets to the computer display, it is correct!
> 
> Which brings me back to my original request for a utility that will 
> allow both DeLorme Street Atlas and NMEATIME to share the single COM 
> port which the computer has. Thanks to all for the numerous suggestions 
> and hints about such programs, I'm evaluating them now, but have not yet 
> settled on one. I'll publish this information back to the SIG when I 
> have decided.
> 
> Incidentally, I do use Socket Watch to keep the computers in the house 
> and connected to the internet on time. That is a great program - highly 
> recommended.
> 
> This SIG is a treasure house of information!
> 
> 73,
> 
> Claude - K5DTN
>  
> */Robert Bruninga <bruninga at usna.edu>/* wrote:
> 
>      > Also, most folks don't realize that "GPS Time"
>      > is NOT Earth time! The GPS constellation does
>      > not follow leap seconds. This has happened
>      > something like 13 times, so GPS time is off by
>      > About that much from official "Earth Time".
> 
>     True about internal GPS time, but I thought they included those
>     offsets into the Display and serial output when they output time
>     so that it is displayed and produced externally to be UTC time?
> 
>     Bob
> 
> 
>     Merely using a GPS
>      > To update your computer's CMOS clock will not make your
>     computer's
>      > Time "correct". A GPS is generally a fantastic tool for a
>     time
>      > "reference", like a 1ppm time base standard, but it's not an
>     earth
>      > clock. You probably will be much better off simply using a
>     NTP
>      > utility to update the computer time from the Internet, such as
>      > "SocketWatch 32" (www.locutuscodeware.com).
>      >
>      >
>      >
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