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[aprssig] Packet Node on 144.390 ?

Joel Maslak jmaslak-aprs at antelope.net
Sat Sep 9 04:36:27 UTC 2006


On Sep 8, 2006, at 10:01 PM, William McKeehan wrote:

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

Some reasons:

Connected mode packet doesn't work well on congested airways.  It  
gets exponentially slower as more traffic is added to the air.  So  
you don't want to mix with APRS for that reason.

Collisions have relatively little effect on APRS - the packet(s) get  
garbled, but the collision doesn't ADD to the traffic (through  
retransmissions) unlike connected mode, where collisions cause MORE  
traffic, causing MORE collisions, causing MORE traffic, etc.

Because there are a lot of stations on 144.39, most probably can't  
hear the others direct.  So the chance of collisions is MUCH higher  
than it would be otherwise.

Perhaps this is an application for APRS bulletins instead?  One  
benefit of bulletins over connected mode packet is that if a lot of  
stations are interested in the bulletins, they don't all need  
individual copies sent to each station.  In addition, they will be  
gated to the Internet without any additional work - unlike connected  
mode packet, opening up other possibilities (a display in the  
county's EOC, without needing permission for additional antennas, etc?).

The existing APRS digis probably aren't configured to allow connected  
mode packet to be digipeated through them.

Do you really want to do connected mode packet on a channel where  
probably half your users are using a radio with a HALF SECOND  
transmit delay?

Additional traffic that D7s and D700s can't decode will make it  
harder for the Kenwood users to see the true APRS traffic.

Connected mode packet through multiple digis is flaky at best.   
ESPECIALLY on a congested channel!  So, you are basically limited to  
using one digi.  If this is for a local group, it might be just as  
good to just colocate the node with the digi, both on different  
frequencies (perhaps use 70cm to reduce interference?)

Speaking of interference, packet on 70cm (or other band) instead of  
2m would mean you wouldn't have nearly the same amount of desense on  
nearby HTs using the club voice repeater on 2 meters...  APRS isn't  
nearly as big of a deal on 2m - one packet every few minutes, vs.  
connected mode packet with much more frequent packets.

One thing you might look at is whether or not there are too many  
extremely high WIDEs - if there are, perhaps you could convert one or  
two of them to another frequency and use them for traditional  
packet.  They are probably hurting the APRS network anyhow.






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