So has AB9NN-9 been to the big Island recently?  I wish!  I did recently meet a new friend from Hawaii though.  But THAT is also not what this blog post is about.  It actually is about the concept of ALOHA Circles.  “The ALOHA circle is that circle that contains the number of users that equals a 100% full channel.” According to http://aprs.org/aloha/ALOHAcir.txt

 

SO what?  The topic is network congestion to the point of network uselessness.  Each person that runs an APRS station must (or should) set the number of times they want their transmission to be repeated (DIGItally rePEATed  by “digipeaters”.  http://info.aprs.net/index.php?title=Digipeater   This is done by setting or configuring the number of “hops” your station requests from the network.

 

Why do you need hops?  Because a radio transmission only goes so far.  If you don’t make the trip to a station connected to the internet (called an iGate) on the first hop, it’s hop again or lose the data.  Thus the need to handle multiple hops.  This is done through the WIDEn-N setting.  As I understand it, a WIDE1-1 is for one hop, a WIDE2-2 is for two hops, etc…    So why not just max out the number of hops?  You know the ham types – biggest amplifier wins…  The problem is – if everyone does this then our APRS radios that are set to digipeat spend all their time re-transmitting data and never get to transmit the fresh data.

 

Thus the need for limits.  http://aprs.org/aloha.html suggests that after there are 60 radios in a given ALOHA circle it becomes degraded.  The number of hops requested by each radio in that circle can have a huge impact on the APRS network performance.  So what are some practical guidelines for Widen-N number settings?

 

Search this page http://www.aprs.org/  for the APRS USER DENSITY map.  Take note of the suggested settings below the map.  I found the suggested settings to be quite informative.  I travel into the U.P. of Michigan and likely will run a WIDE3-3 for such travels.  But a WIDE2-2 is suggested for most people in the southern ½ of Wisconsin.

 

When you click on the vehicle icon for an APRS station in www.APRS.FI it will display their WIDEn-N settings.  I suggest you do some reading on these settings and also talk to other hams to see what their experiences are in the use of their particular settings.

 

I hope that you will use this scarce radio frequency resource with some thought about what you are trying to accomplish and how it will affect those around you.

 

Stay radio active!

 

Jon Kreski, AB9NN-9

http://www.HamRadioResources.com

 


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