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.
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 free 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 Windows, but also Mac and Linux if at all possible so that we are not locked into any single operating system vendor.
The standard software package for digital emcomm in the WPA Section is the Narrow Band Emergency Messaging System (NBEMS). NBEMS consists of four major parts:
  • Fldigi which implements a multi-mode sound-card based modem
  • Flarq, which allows us to use fldigi with automatic repeat requests (ARQ).
  • Flwrap, which inserts checksums into a file so that we can verify that it has been received exactly as it was sent.
  • Flmsg, which allows us to easily send message in various formats like ICS-213 and ARRL Radiogram.
NBEMS may be downloaded from http://www.w1hkj.com. Detailed documentation about how NBEMS is being used throughout Pennsylvania may be found at http://www.paNBEMS.org
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, Windows 7, 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 the 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, Olivia, and error-correcting PSK modes.
  • 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.


The standard mode for use over FM repeaters or on FM VHF/UHF simplex channels is MT632000 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 fairly tolerant of audio levels and does not require precise adjustment of
  • 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


The standard mode for short messages/files and keyboard to keyboard chat over HF/SSB is  Olivia. Experimenting and testing has shown that Olivia has very robust error correction, is  resistant to fading and static crashes, and is very tolerant to mistuned stations. Olivia is a popular mode for recreational HF operation, so we won’t need to relearn how to use it during an emergency.
When conditions are adequate, we will use Olivia with 8 tones within a 500 Hz bandwidth,  abbreviated as 8/500. When conditions deteriorate, we will use 16 tones within a 500 Hz  bandwidth, abbreviated as 16/500. The 16/500 Olivia is more robust than 8/500, but is 50%  slower.
Olivia is a very robust mode and is forgiving of tuning errors. However, it is very slow. This  makes the mode inappropriate for large messages like lengthy bulletins or substantial  spreadsheets.
We will use either MT63-1000 or MT63-500 for large messages on HF, depending upon band  conditions. We have found that MT63 works very well on HF. As with MT63-2000 on  VHF/UHF, we will use 64 bit long interleave and 8-bit extended characters.
There are times when we must be completely certain that a message was received with  absolutely no chance of error. Examples of this are:
  • Spreadsheets containing a roster of evacuees at a shelter.
  • Lists of required pharmaceuticals.
  • Phone numbers and email addresses of critical personnel.

The standard method of ensuring that critical data was received 100% is the Flwrap program.  Flwrap inserts a checksum into a file that is transmitted. The receiving stations compute a  checksum on the received data and compare it to the checksum that was transmitted with the file.
If the two checksums are identical, we can be 100% sure that the file was received without any error.

  • Flwrap will be used to ensure data integrity under the following circumstances:
  • When transmitting critical data where any error is not acceptable.
  • When transmitting data such as spreadsheets where any error could result in file
  • Whenever directed to by the Served Agency.
Flwrap has the ability to compress data. However, extensive testing has shown this is of limited  value. We will consider use of compression only when sending spreadsheets and if compression  reduces the file size by at least 50%.
When we must pass traffic using a standard formal format, either at the request of a Served  Agency, or by mutual agreement, we will use the Flmsg package.  Flmsg allows us to easily send messages in a variety of formats such as ICS-213, other common  ICS forms, ARRL Radiogram, and even plain text. Flmsg greatly simplifies the workflow to  send and receive data with a minimum number of clicks, and is integrated with Flwrap and  Fldigi. Flmsg also allows us to obtain high-quality output that can be easily printed. The ARRL  Radiogram portion of Flmsg simplifies many aspects of writing messages in NTS format, such  as automatically computing the message’s check count (CK), and simplifying lookup of handling  instructions and ARL messages.
Transmission of binary files such as Word documents or Excel spreadsheets is to be discouraged  because of the large size of these files and our limited bandwidth. Instead, we should convert  Word files to text format and Excel spreadsheets to Comma Separated Values (CSV) text format.
For example, an Excel spreadsheet in its native binary format may be 12 kB in size, but only 2kB  when exported to CSV.
The necessity for discouraging the use of binary files should be discussed during planning  sessions with our Served Agencies so that we can set expectations in advance and not be  surprised during a disaster or incident. We should also encourage our Served Agencies to  provide us data as digital files whenever possible and not as paper. This will result in a faster  and more accurate workflow, and will place the responsibility for any errors in the data upon the  Served Agency and not on the amateur radio operator.
During an incident we may need to activate a digital net. On VHF/UHF we will use the same  procedures that we use for voice nets because we are allowed to intermingle digital and voice  communications.
County Emergency Coordinators should designate one repeater and one simplex frequency for  their county as digital VHF/UHF channels. The EC should seek permission from the repeater  trustee and not allow digital transmissions through the repeater prior to obtaining authorization  from the trustee. Regular tests and drills should be performed using authorized repeaters to  ensure that there are no issues such as transmitter timeouts that would cause potential problems  with digital transmissions. The standard simplex frequency and the repeater designated for  digital use shall be reported to the Section Emergency Coordinator (SEC) so that this information  can be shared across Western PA.
The increase in stations using NBEMS on HF has caused us to rethink and re-write our HF net  procedures. These procedures are evolving and we may decide to more fully document them in a  separate standard once they have stabalized.
The standard HF digital emcomm frequency for Western PA is 3.583.5 MHz with 7.073.5 MHz  as a backup frequency. These frequencies are dial frequencies for the HF rig VFO in USB mode  with a center waterfall frequency of 1000 Hz.
Depending upon the anticipated number of check-ins, the Net Control Station (NCS) may decide  to ask for check-ins by stations with emergency and priority traffic first, stations with other  traffic next, and then by ARES Region or other criteria as established by NCS. Stations are to  follow the NCS’ instructions on when to check in.
When checking in, stations will transmit only their callsign, county, and a statement of traffic.  The statement of traffic will consist of the number of messages and the callsign of the station to  receive the traffic. For example, if W3YJ is checking in and has one piece of traffic for  KB3FXI, W3YJ will check in as follows:
W3YJ, Allegheny, 1 KB3FXI
After listening for check-ins, NCS will acknowledge stations that have checked in and may ask  for relays.
Should a station need to get the attention of NCS for a break-in, the station will transmit a carrier for 5 seconds.
The initial mode for the HF net will be 8/500 or 16/500 Olivia, depending upon band conditions.   Should it be necessary to change modes to MT63-1000 or MT63-500 to pass high-speed traffic,  NCS will announce the change in mode and then transmit a carrier at 1000 Hz in the waterfall for  20 seconds. Stations will change modes and center the 1000 Hz carrier in their bandpass.
This is an evolving standard already in its third iteration. It will continue to expand and change  as we learn more. 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  paNBEMS working group and get involved with the mailing list and testing.
Version 3.0, 11 Dec 2010
Harry Bloomberg W3YJ, Assistant SEC WPA Section


  1. I gotta be careful what I write, somebody might actually read it! This is great seeing this posted here, I’m glad to see it’s useful to somebody, please let us know what does and does not work for you.

  2. Steve L. says:

    Its a learning curve. Local ARES is not into digital so once I get a feel for it I’m going to do a presentation using the PowerPoint I can’t seem to find now. Just changed QTH and big pine tree begs for an antenna but the weather is between -30c and +5c depending on what has to be done (Murphy Scheduling Rule)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s