APRS Best Practices

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KD7CAO
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Joined: Wed Feb 18, 2015 2:58 pm
Location: Krugerville, TX

APRS Best Practices

Post by KD7CAO » Tue Jun 30, 2015 3:33 pm

Since it is highly recommended we all have APRS capability for Skywarn use I thought it would be useful to post some information on the "Best Practices for APRS."

First, APRS is Automated Packet Reporting System there is some literature out there including an ARRL and W5YI license manual that both think the "P" stands for "Position" according to the inventor of APRS Bob Bruniga it is Packet. Granted most users use it in conjunction with a GPS to beacon positions while driving, flying, ballooning, and other uses but it has many more capabilities than that.

Second, you must be careful which literature you are going to follow on the proper setup of your APRS station. The functionality and methods were changed around the year 2006. It helped to reduce some of the issues that were being experienced from trackers that did not have a true receiver built in. Devices such as the TinyTrak by Byonics is one such unit where a Carrier Detect was used instead of a true decoding technology. If setup incorrectly it has the ability to beacon on the frequency causing collisions.

Finally, with the heavy saturation of APRS users in the DFW area we have begun using two frequencies the nationally recognized 144.3900 MHz and the alternate 144.3400 MHz. In addition, we are starting to see users expanding to UHF where operation is not as prevalent but interest is growing.

A long list of information may be found here: http://www.arrl.org/position-reporting-with-aprs but below I hope to condense this into recommended settings.

Your Callsign should be used in the callsign slot, unless the use of tactical calls is needed for special events. In that case you should put your callsign in the BTEXT field and set it to auto beacon every 1 transmission. This ensures that if your last transmission will always be with your callsign.

The SSID is a number from 0-15. Here is a list to help choose which SSID would be the most appropriate, however most users have more than one so the numbers just increase. It is not a requirement but, can be helpful:

SSID RECOMMENDATIONS: It is very convenient to other mobile
operators or others looking at callsigns flashing by, to be able to
recognize some common applications at a glance. Here are the
recommendations for the 16 possible SSID's (the limit of 16 comes
from the 4 bits available in the AX.25 protocol. Note, The SSID of
zero is dropped by most display applications. So a callsign with no
SSID has an SSID of 0.

-0 Your primary station usually fixed and message capable
-1 generic additional station, digi, mobile, wx, etc
-2 generic additional station, digi, mobile, wx, etc
-3 generic additional station, digi, mobile, wx, etc
-4 generic additional station, digi, mobile, wx, etc
-5 Other networks (Dstar, Iphones, Androids, Blackberry's etc)
-6 Special activity, Satellite ops, camping or 6 meters, etc
-7 walkie talkies, HT's or other human portable
-8 boats, sailboats, RV's or second main mobile
-9 Primary Mobile (usually message capable)
-10 internet, Igates, echolink, winlink, AVRS, APRN, etc
-11 balloons, aircraft, spacecraft, etc
-12 APRStt, DTMF, RFID, devices, one-way trackers*, etc
-13 Weather stations
-14 Truckers or generally full time drivers
-15 generic additional station, digi, mobile, wx, etc

In addition to the 16 SSIDs shown above you may see some letter SSIDs displayed online or in your radio's display when receiving traffic. Some of the digital modes such as D*STAR use a letter to identify the different radios. This should not be used for non-D*STAR radios however as it would let users believe you are operating on the DPRS network and your information is being ported to APRS.

The Path portion has been a bit of contention for many users. This has changed in recent years as the original path was something like RELAY,WIDE,WIDE. This created a continuous broadcast which is explained here better than I can do it: http://wa8lmf.net/DigiPaths/ NOTE THIS PATH SHOULD NO LONGER BE USED UNDER ANY CIRCUMSTANCES!

The new correct path for the DFW path would be something like: WIDE1-1,WIDE2-1 this is considered to be the N-N type path this helps the newer APRS digipeaters reduce the number of hops needed with the goal of trying to get a message iGated and reduce network congestion. In addition, the Raspberry PI TNC setups we are utilizing in the DCARA nodes at TWU, Rosston, and Guy runs at home are designed to fix bad packet paths and clean up the network.

So the recommended settings would be as follows:
MOBILE STATION: WIDE1-1,WIDE2-1
FIXED STATION (HOME): WIDE2-1
AIRBORNE STATION: (NO PATH) or (WIDE2-1)
if selecting NO PATH just leave the field blank, this keeps the wide area congestion down as many stations may pick up on the broadcast. However, if you want to have ground transmissions while taxiing then the use of WIDE2-1 would give you the best option.

I hope this helps clear things up.
Eric M. Gildersleeve KD7CAO
Krugerville, TX

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