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[aprssig] Packet Node on 144.390 ?

Geoffrey Dick wa4ikq at nevets.oau.org
Sun Sep 10 12:07:23 UTC 2006


Subject: Re: [aprssig] Packet Node on 144.390 ?

William McKeehan, KI4HDU wrote:
> I'm really looking for reasons to give someone to NOT put a packet 
> node (BBS or just PBBS) on 144.39.

This largest reason I can think of is that packet bulletin board traffic
would block time-sensitive APRS information.   Position and weather fall
in this category.  Unconnected APRS packets are less than a second long,
and are not retransmitted. If the channel is busy, an APRS station will
delay to a set interval for fresh position or weather information.  If 
the channel is busy, then time-sensitive information is permanently lost.
   
Each transmission is unique for those who can receive them, and each 
APRS packet burst is separated by minute to several minutes to allow 
others to share the channel.  With DCD taking precedence, Connected 
Packet will impede others from sharing the channel. 

Simply put, are speaking of two AX25 packet operating modes competing 
on a single frequency: 

    connected-long-burst verses unconnected-short burst  

Two connected Packet stations, transmitting, confirming, and retransmitting 
will tie up the frequency for several minutes, preventing a multitude of
short-burst APRS stations from sharing the channel.  This is not a good 
plan for a shared frequency of 10 to 250 active stations in an ALOHA circle. 

Kind regards,

Geoffrey Dick, wa4ikq
Winter Park, FL





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