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hams use coax to transfer high frequency electromagnetic energy between antennae and receivers and transmitters
Sep 29, 2008
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APRS EmComm.
a tactical communications solution ...

Guest speaker . . .
Tim Cunningham - N8DEU .

Tim Cunningham

Tim is considered by many as the local 'Packet Guru'.

He is also known as an Area Coordinator for AMSAT Field Operations.

A presentation of APRS as a tactical EmComm solution,
from an article submitted to the Huntsville Amateur Radio Club, by N8DEU.
(appeared originally in the HARC-VOX newsletter for July 2008 pages 5,6 &7)

- this article was prompted by Doug's ARES District 6 article
in the HARC-VOX newsletter for April 2008.
-Doug Hilton < WD0UG > was discussing the value of effective NCS protocols
.
- Tim has graciously allowed SomeNet to re-publish this article.
(this is part < 1 - 2 - 3 > of a special series)
I read Doug Hilton’s comments from the “ARES District 6” article in the VOX from April with great interest. It was clear to me that the APRS Tactical Communication system can easily fix just about all the problems on the Emergency Net. Having to repeat callsigns 5 or 6 times to check into any net is unacceptable. Not being able to get HAM’s to use the proper international phonetics is just another confirmation that we are all human and suggests we need better methods. Have I failed to communicate effectively over the years that we already have an effective communication tool in our Amateur Radio tool box? APRS can solve these issues and provide an effective tool that has been addressing those needs for many years.

Now that I have cleared my lungs, lets take a look at the ways APRS addresses each of the points that were made in the ARES District 6 article in April’s VOX:
  • 1. NCS making 5 or 6 attempts to get the correct callsign from check-ins.
  • 2. Operators using unconventional phonetics.
  • 3. Priority messages wait for 10 or 20 stations to check-in.
  • 4. Taking check-ins is a time consuming process to get name, location, and callsign correct.
  • 5. Delay time between check-ins.
  • 6. Inefficient transfer of information.
The APRS tactical communication system addresses each of these points and many more. How does it address these points?
  • 1. Getting the correct callsign is a thing of the past unless the sending operator mistypes it. The APRS network will quickly sort out multiple check-ins as the same time. 10 or 20 stations could be logged into the network in a fraction of the time it takes to do it by voice. The bottom line is there is 10-100 times more bandwidth available for the important information from multiple stations. Emergency traffic can actually be passed while stations are checking into the net very easily.
  • 2. There is no need for phonetics in the APRS world. What you see on the screen is what you get. In addition, there is no need to write anything on paper at the NCS station when using APRS, because it can be logged automatically in a file for archival or sent to a printer for automatic documenting.
  • 3. Priority messages suffer due to the way a voice network and human interaction work. This is the most limiting factor of any voice network. It is only as good as the operators and the protocol allow it, but it is a time consuming process. Priority traffic on APRS is built into the core operation of the system. New traffic takes precedence over older traffic. Some may argue that APRS uses an un-connected protocol. This is true and it is the main reason that it is so efficient. New messages take priority and traffic is re-transmitted by an decaying rate while new messages are re-transmitted more often taking priority. Personal messages are acknowledged by sending a message back to the sender to stop sending it. Bulletin messages are the beauty of APRS as they are sent in the same decaying rebroadcast format and everybody receives it virtually at the same time with the broadcast protocol. Thus, newer bulletins take priority in any time critical event. These messages DO NOT wait for check-ins or anybody else. They are multiplexed in between check-ins in case of a REAL emergency situation. I can remember on the old connected packet BBS network when weather bulletins took forever. When the weather was bad the number of bulletins brought the network to a crawl. It would take all night to get all the weather traffic using that old protocol. Today, we utilize that same equipment employing the APRS unconnected packet protocol and that problem is gone. Weather bulletins are sent in real time from the NWS and broadcast to every APRS packet station for all to receive immediately. With some weather bulletins you will be informed exactly how far and in what direction you are from the maximum area of concern. This is immediate information and it waits for no operator to send the message or announce it over a voice repeater. How many times have we experienced storms in our area and the voice net woke up after the threat had passed through the area. This simply does not happen with APRS because APRS users are informed immediately as those NWS messages are broadcast. In fact, with all the weather nodes available on APRS you can set trigger points for wind speed, temperature, and barometric pressure to sound an alarm on your APRS station remotely.
  • 4. With APRS you can reduce the check-in time to a fraction of what you experience today. If those 10-20 check-in stations used the APRS network, the check-in time could be less than 2 minutes, nobody would have to repeat their information (unless they typed it wrong), your location information would be automatic and your APRS symbol would be placed on the map. I know I have refrained from checking into the voice net many times because of the lengthy process. Any station can send priority traffic at any point, even during the check-in process. It is easy, effortless, and better utilizes the bandwidth for increased traffic when needed. Voice nets will never compete with the speed of traffic passing on the APRS digital network!
  • 5. The delay between check-ins is a waste of bandwidth. There will be dupes on a voice network and there will be dupes on an APRS network. The advantage is the APRS network automatically takes care of those dupes rather quickly by the design of the protocol and no human intervention is required. Any delay is wasted bandwidth that can be used more efficiently to transfer information.
  • 6. Inefficient transfer of information on a voice network can be a thing of the past with the APRS network. Information is sent as the sender intended. No repeats are necessary that the protocol does not already address.

After digesting this material, I read Rolf’s article titled “Madison County ARES / RACES Update” in the April VOX concerning weather spotter training. Here is another example of where APRS is a practical tool for the services of the Amateur Radio Community. APRS is already weather oriented. No other tool in the Amateur Radio Community contains the weather reporting capabilities of APRS. NWS weather bulletins are broadcasted in real time on the APRS network. Those who utilize APRS maps will see counties highlighted in red or yellow indicating areas with watches or warnings posted in addition to the bulletin itself. You always know how far you are located from the maximum area of concern. All this information is available on the APRS radio network as well as the Internet APRS network since they are seamlessly integrated. Weather is unpredictable at times and the APRS tactical communication system fits the mold on VHF or UHF to contain traffic to a specific area or event. The Internet is nice but it is not required in a tactical communication system where digipeaters can be easily installed to make any necessary connections with conventional radio equipment. APRS knows where you are located, which takes away any guesswork by simply looking on a map and physically seeing your location relative to any activity that may be of concern. In the end, APRS is really an informational awareness system and it performs its function very well.

What better tools do we have for a tactical communication system? The APRS infrastructure has grown and continues to grow in popularity with new digipeaters being added to this tactical communication system. We have solutions to serve the public interest not just a bunch of toys. Although, APRS is a pretty cool toy.

Am I picking on the HAM radio population? You bet! The status quo or old fashion methods may be a little dated for our nets to run efficiently. Does this make you mad? It should! It should make you so mad that your blood starts pumping uncontrollably to the point you get on you feet and think about the problems and the solutions. If we do not have the solution, then what service will replace us along with our valuable radio spectrum? How do you spell the value of Amateur Radio?

Happy APRS Packeting
73’s de Tim - N8DEU

 
When All Else FailsHuntsville-Madison County EMA
The local ARES/RACES organizations are consolidating some of the overhead associated with registration and training of the membership. Join us on the 2nd Thursday evening of each month for a good meeting at the HMC EMA EOC (and learn more about this).
Remember, the severe weather season is available year-round.

digital radio messaging
Additional discoveries, rants and raves, and experiments :
+ Be sure to check www.somenet.net for interesting articles inbetween updates to this page.
+ NBEMS = Narrow Band Emergency Messaging System - check it out (new Yahoo group)
+
VHF Propagation Map = using APRS beacons to visualize current propagation conditions.
+ APRS.FI = another view of the APRS-IS database, from Finland.
+ CWOP = My weather instruments are still active and logging.
although I'm not yet satisfied with the radiation shield I made for the external thermometer.
The reading is too high in full sun. (check my conditions via FindU).


Previous pages from the archives :
2008 . . .
2007 . . .
2006 . . .
+ 2005 . . .
Additional organizations, projects and web sites that I continue to support and promote :

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