[aprssig] APRS on UHF?

Scott Miller scott at opentrac.org
Wed Nov 26 14:30:29 EST 2008

And aside from that, for slotted ALOHA it's the 1pps output you need. 
The idea is that since you probably can't hear the other users of the 
channel anyway, it's better to step on one discrete time slot and cause 
only a single collision rather than clobbering multiple packets.

I think there are better ways to do channel access control, but slotted 
ALOHA doesn't require any real coordination.


Iain Young, G7III wrote:
> Patrick wrote:
>> GPS time sync is nice, but it doesn't handle when they don't have the same time...  I've
>> got a handful of GPS models and some have different time then the others...  All I can
>> figure is that the mfr's have taken into account leap seconds in code or something along
>> that lines..
> Urm, they shouldn't have. Or rather they should let the GPS fleet tell
> them the GPS offset from UTC. IIRC, Currently, I think there is 14
> seconds difference between GPS and UTC.
> If your difference is -not- 14 seconds [maybe 13 with older devices],
> then it's something other than leap seconds.
> I had this very discussion the other night while out at a works do.
> Thing is, if the GPS time is off on the device, I can't see how
> the location can be at all accurate.
> My guess would be that some devices have a seperate "Real-Time" Clock
> on board, and are reporting that time, rather than GPS time.
>  From what I understand, the Megallan<SP> models, I know have an issue
> with keeping time, at least according to my colleague the other evening.
> 73s
> Iain
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