[aprssig] AX.25 Digipeating precise timing?

Lynn W Deffenbaugh (Mr) KJ4ERJ at arrl.net
Mon Jul 22 19:08:13 EDT 2019

Also keep in mind the Kenwood D710 digipeating bust:  A radio will 
digipeat its OWN packet if it receives a digipeated copy of it with hops 
remaining.  In other words:

GDHILL-8 transmits packet X with HOP7-7,HOP7-7 and is enabled for HOP 
MDMTNS-7 digipeats the packet with HOP7-6,HOP7-7
GDHILL-8 receives that, and digipeats it as HOP7-5,HOP7-7.
MDMTNS-7 receives the digipeated packet but does NOT digipeat it again 
because it is in the recently digipeated list.

The issues is that originated packets are NOT put in the recently 
digipeated list, which IMHO should be a recently TRANSMITTED list to 
include originated packets as well as digipeated packets.

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

On 7/22/2019 12:15 PM, Robert Bruninga wrote:
> AX.25 experts needed:
> We finished the Appalachian Golden Packet event with 15 hops to Maine and
> 14 hops back to Georgia.
> At 9600 baud each packet is 0.5 seconds and we think we can increase
> throughput significantly by totally changing our beacon plan, messaging
> plan and getting the 2X benefit of 9600 baud.
> This means we would like to better understand the exact AX.25 packet
> timing.
> I just timed 9600 baud packets between three kenwoods as digipeaters and
> conclude an end to end packet with no collisions woiuld take about 8
> seconds.  I want to analyze the probability of success with say a packet
> starting at each end and meeting in the middle, what is the chance of
> anialation of one, or both.  This depends on the delay that all
> digipeateers (with Dwait off) will wait before transmitting.  It is only
> during this window when a given digi, could hear two packets before it
> transmits.
> Anyone remember this stuff?, or am I starting from scratch..
> Radios are set to TXD of 200ms...  But that is after the radio is already
> keyed.
> Bob, Wb4APR
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