[aprssig] KPC3+ induced errors

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Wed Mar 16 16:27:17 EDT 2011

Caveat Emptor:  I'm not the expert, but...

On 3/16/2011 3:28 PM, Larry Cerney wrote:
> Just for my own education, just where in the APRS system is dup checking
> done?

Dupe checking is done in the APRS-IS server, typically javAPRSSrvr.

> What is monitored in the packet to identify a dup?

The fromCall, toCall, and payload.  The path is NOT included in the 
dupecheck as it varies as digipeaters and IGates handle the packet.


> How long does the "dup window" remain open?

The default dupe check window is 30 seconds.  Any packet delivered to 
APRS-IS later than 30 seconds after the first delivery of the same 
packet will be passed on into the network.

Delayed dupe introduction is easier to trace with packets that contain 
timestamps.  The raw NMEA GPS strings include the timestamp so they will 
be easy to see the duplicate deliver vs time time of entry.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

> Larry K0ANI
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