APRS TNC Settings

| June 3, 2019 | Training | No Comments

Whether it is a hardware or software defined TNC,  the key part of APRS is the Path.  This setting allows your packets to be repeated (digi-peated) around the network, but also control how many times so that your transmission does not cause unnecessary hops, contributing to channel congestion.

Setting up your path is important in APRS – the internet is a good place to start, but be careful of old websites.  Below are the Path setting recommended for stations in the Omaha Metro Area.

Today’s recommended universal path settings under the “New Paradigm” are:

  • WIDE1-1,WIDE2-1  (Will produce two hops and will take advantage of home fill-in digis. Use in busy urban and suburban areas.) This is recommended for all mobile setups. 
  • WIDE1-1,WIDE2-2 (Will produce three hops and will take advantage of home fill-in digis. Use for mobile operation in rural areas with low APRS activity only!)
  • WIDE2-2  (Shortest path string. Produces two hops by directly using two high-level digis. Will work almost anywhere but especially recommended in the where high-level digipeaters are really high-level; i.e. on mountain tops thousands and thousands of feet above users that can easily be reached directly, without the help of home stations. – This is not the case in our local area.) However WIDE2-2 is the ONLY path that works with digipeaters in southern California. So a
  • WIDE2-1  only  (This should be used by fixed stations, and will produce only one digipeater hop.  In most cases, fixed stations already have the advantage of a better antenna and elevation than a mobile, and should be able to reach a true wide-area digipeater without the aid of another home station.)
  • Airborne stations above a few thousand feet should ideally use NO path at all, or at the maximum just WIDE2-1 alone.  Due to their extended transmit range due to elevation, multiple digipeater hops are not required by airborne stations.  Multi-hop paths just add needless congestion on the shared APRS channel in areas hundreds of miles away from the aircraft’s own location.  NEVER use WIDE1-1 in an airborne path, since this can potentially trigger hundreds of home stations simultaneously over a radius of 150-200 miles.
  • NEVER put WIDE1-1 in a path anywhere but the first position of a new standard path.  (I.e. never after WIDE2-1, etc.) If you do this, dozens (or hundreds) of home stations within earshot of one or more WIDEs will needlessly clog the channel retransmitting the WIDEn-N’s packets for no reason.
  • Paths longer than about WIDE3-3 are almost completely useless. The probability of success goes down exponentially as the area covered by the transmission expands outward, and the packet is exposed to more possibilities of random collisions with users in distant areas. On the other hand, you can create literally thousands of useless packets for every transmission, as the UI flood spreads outward over hundreds of miles in every direction. In many areas, intelligent digipeaters are now automatically reformatting excessively long or abusive paths to something more reasonable such as WIDE2-2 or WIDE3-3. (Or simply ignoring anything over WIDE2-2 entirely).