Alabama APRS Guidelines

The site is set up to help facilitate ALABAMA APRS Digipeater Owners and Users to understand the basic APRS Guidelines.

Mobile Stations:

- 1 hop: Use WIDE1-1

- 2 hops: Use WIDE1-1,WIDE2-1 (Higher reliability using fill-ins)

- 2 hops: Use WIDE2-2 (Slightly more efficient if WIDE1-1 relay not needed)


Fixed stations

- 1 hop: Use WIDE1-1 (only if you cannot hit a WIDEN-n digipeater directly)

- 1 hop: Or WIDE2-1 (if you can hit a WIDEN-n digipeater directly)

- 2 hops: Use WIDE2-2

- 3 hops: Never. If you need to go 3 or more hops, then chose a SPECIFIC path in a given direction using specific digipeater call-signs. Do NOT flood an entire state or area just to talk to a station in one direction. For organized tactical communication events there are exceptions.


- Use WIDE for UITRACE function (WIDEN-n)

- Use AL for UIFLOOD function (ALN-n)

- Both UITRACE and UIFLOOD must be set up for callsign substitution for paths to be traceable (this is mandatory). It is not acceptable to have a digipeater set up without callsign substitution as it may cause duplication of packets on the network. The beauty of the 2005 New-N paradigm is that all packets are now TRACED and contain the PATH they took to reach you. If you need to talk to someone at a distance, reverse the path using the specific digipeater callsigns.

- Do not support digipeating of RELAY, WIDE, or TRACE paths. These are obsolete and some units cannot perform callsign substitution on these paths.

- Digipeaters should never delay digipeating a packet. For connected packet networks this may be desirable but not for unconnected networks like APRS. This means DWAIT parameters should beset to 0. Parameters like Persist and Slot should be set to 255 and 1 respectively or whatever it takes to avoid a digipeater from delaying a packet. This is UI network where digipeaters never delay retransmission of a packet. Delays of up to 2.5 minutes and longer have been observed on improperly configured systems. This will cause a mobile station to ping pong across a map on the APRS-IS due to delayed packet transmissions. Digipeaters wait for nothing to retransmit a packet.

- Digipeaters should observe the ALOHA range. In other words digipeaters are set up in a cellular method. Extremely high digipeaters are not desirable.

- Digipeaters should make an attempt to limit traffic to 2 hops. Some advanced digipeaters have hop count limits that prevent a station using WIDE3-3  or higher from traveling more that 2 hops. For digipeaters that do not support this function you can place WIDE3-3, WIDE-4, WIDE5-5, WIDE6-6, and WIDE7-7 in your UIDIGI CALL list to limit them to 1 hop until they get the message and conform to less abusive paths. Education of proper path settings is the key to success. It is not necessary nor desirable to place a hop count limit on the ALN-n in-state traffic.

The general goal for any station is to reach an IGate. The majority of IGates can be reached with 2 hops or less. IGates are HUB connectors to long distance stations where traffic is passed over the APRS-IS to an IGate local to that station. Increasing the number of hops only causes QRM to APRS networks more than 2 hops away.


Weather Stations

- 1 hop: Use AL1-1 or WIDE2-1

- 2 hops: Use AL2-2 or WIDE2-2

The use of ALN-n limits the data from traveling over state boundaries and robbing bandwidth from distant APRS networks. The use of WIDEN-n paths can be utilized when a station is within ~10 miles of s state border.

- The frequency of weather information should be limited to no less than 444 seconds or 7 minutes and 24 seconds. This allows for 2 transmissions in a 15 minute period. Transmitting data less than this time is not productive for weather agencies like NOAA or Meteorologists. The reason for time limitation is simple. The FINDU server collects data from the APRS-IS and sends it to the MADIS server every 15 minutes. The Mesonet gets data from the MADIS server and this data is then available for the weather agencies to see it. Thus, sending weather data via the APRS RF network more frequently than 2 times in any 15 minute period is not productive unless your weather agency is set up to collect this data from the RF network or the APRS-IS. I only know of one weather office that has entertained this idea.


These guidelines have been prepared to assist all setting up an APRS station in the state of Alabama. The goal of these guidelines are designed to help build a solid APRS network foundation in the state of Alabama.



If I have missed something, please drop me a note (N8DEU at ARRL dot NET).

This page was last updated on 21-Aug-2013