WPA Section Standards for Digital Emcomm

Version 0.1
21 Dec 2024
Harry Bloomberg W3YJ
Assistant SEC WPA Section

Why standards?
Guiding Principles
Standard Software Package: NBEMS    (Links to Web Site)
Standard Mode for VHF/UHF FM: MT63-2000 Long Interleave
Standard Mode for HF with Strong / Poor Signal Strength:
Where Do We Go From Here?
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Why standards?
An incident or disaster is no time for experimenting. Time and effort must not be wasted in getting on the air and sending traffic. We must minimize the amount of time needed to refamiliarize ourselves with techniques and methods that we may not use often in our everyday amateur radio activities. We must also be sure that all ARES groups within the WPA Section can easily communicate with each other and help each other.
One of the keys to digital emcomm success is the adoption of standards. Once standard software packages and digital modes have been agreed upon, we can train on these methods, have documentation prepared in advance and available in EOCs and go-kits for use during an incident, and train a large pool of operators who are knowledgeable in these common practices who can be easily "plugged into" a deployment team.
Standards can sometimes be controversial. It's been said that between two hams there are three opinions. Discussions about techniques and modes can sometime reach a religious fervor. But decisions must be made, otherwise we won't be ready when called upon to serve and we will run the risk of not being able to communicate with each other.
These standards have been adopted based upon experience in drills and actual events. But these standards are not carved into stone tablets. Should there be a difference of opinion, we are willing to listen to constructive criticism. But there must be standards, otherwise we will run the risk of chaos during an incident.
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 Guiding Principles
  
Whenever possible, these standards have been guided by the following principles:
 
  • Standards must be inexpensive to implement and not require the build-out of an expensive digital infrastructure.
  • Whenever possible, we should use tools that amateurs can use for both emcomm and daily amateur radio activities.
  • Digital modes should use error correcting protocols.
  • Tools should be relatively simple to use for those who are not computer experts.
  • Tools should allow for flexibility of use under varying conditions with different models and types of radios.
  • Software packages should be cheap or inexpensive and not be encumbered by license, patents, or restrictive terms of use so that we can install them on as many systems as possible, including systems provided by served agencies.
  • Expensive and specialized add-on equipment like external modems is to be avoided.
  • Software should work on not just on Windows, but also Mac and Linux if at all possible so that we are not locked into any single operating system vendor.
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Standard Software Package: NBEMS
The standard software package for digital emcomm in the WPA Section is the Narrow Band Emergency Messaging System (NBEMS). NBEMS consists of two parts:
 
  • fldigi which implements a multi-mode sound-card based modem
  • flarq, which allows us to use fldigi with automatic repeat requests (ARQ).
NBEMS may be downloaded from http://w1hkj.com/NBEMS/.
Detailed documentation about how NBEMS is being used in Western PA may be found at http://www.pa-sitrep.com/NBEMS/index.html.
We have selected NBEMS for the following reasons:
 
  • Based upon extensive on-the-air testing, the package is stable and easy to use.
  • Runs on Windows XP, Vista, Linux, and Mac, so we have little problem with "it won't run on my computer!"
  • Cost is FREE.
  • Is released under the Gnu Public License (GPL). It is unencumbered by licenses or patents, so we can easily and freely redistribute it to other amateurs and install it on computers of served agencies when necessary.
  • The package is Open Source, meaning we can see and modify the source code. This protects from being dependant upon a commercial vendor who could go out of business or change terms of use.
  • Is supported by a large and active user community.
  • Works with any radio on VHF, UHF, and HF, also with SSB and FM.
  • Does not require a large build-out of potentially expensive fixed-location digital assets.
  • Allows us to pass data over existing FM repeater network. We can use any repeater for both voice and digital communications. This leverages our investment in our existing analog repeater infrastructure and gives us maximum flexibility in how to use a channel.
  • Supports popular amateur modes like PSK31 and RTTY, so we can use it for our every day amateur activities, unlike systems dedicated for emcomm use only.
  • Supports modes appropriate for emcomm use like MT63, Oliva, Domino, and MFSK. Through use of macro keys, and be easily customized for digital emcomm use.
  • Other than a computer and a soundcard, no additional hardware is required.
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Standard Mode for VHF/UHF FM: MT63-2000 Long Interleave
The standard mode for use over FM repeaters or on FM VHF/UHF simplex channels is MT63-2000 with long interleave.
We have selected this for the following reasons:
 
  • Data redundancy in both time and frequency. Experience has shown that a 1-2 second drop of signal can occur and we will still have 100% copy.
  • Among the fastest of the soundcard modes.
  • Can be used with acoustic coupling to an FM radio. One does not need a hard-wired computer-to-radio interface. One can hold a radio's microphone up to a computer's speakers and hold the computer's microphone up to the radio's speakers and have success in transmitting and receiving data.
  • Mode is very tolerant of audio levels and does not require careful adjustment of levels.
  • Although a carefully calibrated soundcard is desirable, experience has shown that the mode is tolerant of soundcard timing.
  • Testing has shown a very high probability of 100% copy without use of an ARQ layer.
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Standard Mode for HF With Strong Signal Strength: DomininoEX11(FEC)
The standard mode for use over HF when we have good HF conditions is DominioEX11, transmitted as upper sideband.

We have chosen this mode for the following reasons:
 
  • Mode allows use of Forward Error Correction (FEC), increasing the likelihood of 100% copy.
  • Mode provides for the display of a short tactical identifier. This may prove to be useful during an incident.
  • Better throughput than Olivia.
Standard Mode for HF with Poor Signal Strength: Olivia 500/16
The standard mode for use over HF when we have poor HF conditions is Olivia 500Hz wide with 16 tones, abbreviated Olivia 500/16. Experimenting and testing has shown that this mode works extremely well under poor band conditions. Unfortunately, this is a very slow mode, so it should be used only as a last resort, or if the traffic to be sent is very short.
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Where Do We Go From Here?
This is an evolving standard. It will be expanded as we learn more, particularly as we gain experience on HF where we have the most to learn. This is also an open standard. Although at times decisions will have to be made by ARES leadership, it is hoped that we can arrive at these standards through consensus and open-minded constructive discussion, and that these decisions can be validated through on-the-air testing. The best way to participate in the standard-setting process is to join the wpa NBEMS group and get involved with the mailing list and testing.
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