Digital Communications Capabilities for Prepared Families, by Prairie Dweller

As most preppers know, regardless of where you are on your prepping journey, the ability to communicate is a vital need. We need to communicate with our families, and we need to get information about what’s going on around us. The need for communications, as well as the traditional methods for establishing them, has been well addressed in preparedness circles. What has not been addressed much is what digital communications capabilities have to offer you as a prepper. I have been an amateur and commercial radio operator for many years, and the capabilities of digital communications as compared to voice communications astonishes me still.

Digital communications involves the interconnection of computer hardware and radio equipment in order to send and receive messages that are generated by a computer by utilizing radio transmissions. While analog voice communications have their place, digital communications offer the ability to send messages over short or long distances, using reliable error correction, under less than ideal conditions. Many times, especially on the high frequency (HF) bands, propagation conditions can be challenging and voice communications can be delayed, insecure, and inefficient. The utility of digital modes is not confined to the HF bands, as newer models are very effective on higher frequencies in the very high frequency (VHF) and ultra high frequency (UHF) bands.

Many years ago, digital communications modes required expensive, external computer hardware called a terminal node controller (TNC).That has now changed, with the advancement of computer technology. Digital communications modes now utilize audio sampling software and the on-board computer sound card to receive signals from within the typical noise floor, where voice communications would not be possible. The digital software is typically free, and the only audio processing equipment that is needed is the sound card that is already integrated into the vast majority of computers, including desktops, laptops, and some tablets. A simple interface device is also needed in order to interconnect the computer and the radio.

To start working with digital communications, you need a computer with a sound card, a radio transceiver, and an interface between them. There are many popular software suites for amateur radio digital communications. I have experimented with most of these and have found the FastLight (FL) modem software to be best suited for emergency communications (EMCOMM). The FastLight software is also known as narrow band emergency messaging software (NBEMS). The individual programs included in NBEMS are FL-DIGI, FL-MSG, FL-AMP, FL-ARQ, and FL-RIG. Download links to that software can be found at At a minimum, I would recommend installing FL-DIGI (which will automatically install FL-ARQ), as well as FL-MSG. As your confidence in using the basic software grows, you can then learn to operate the advanced features of FL-AMP and FL-RIG. FL-AMP allows full error correction between two stations, which guarantees 100% correct message delivery. The same cannot be said for voice communications or even morse code (CW). FL-RIG software allows you to remotely control your radio from your computer, if you choose to do so.

After FL-DIGI is installed, you’ll need to take some time to get to know it. A very good training video can be found at You Tube. You’ll need to configure FL-DIGI to your specific installation, including what sound card you are using, as well as how you want FL-DIGI to make your radio transmit when it needs to. In order to get the transmit and receive audio to flow from the radio to the computer and in order the make the radio transmit upon command from the computer, you’ll need a digital interface. Several types of these devices are available, such as the Tigertronics SignalLink, the West Mountain Radio Rig Blaster, or the BUXCOM Rascal. For the new digital operator, the SignalLink is the easiest to set up, and it includes an actual external USB sound card within the device and external controls that can be easily manipulated. This allows you to leave your on-board computer sound card available for other uses. The SignalLink also does not require a serial port on your computer. Most computers no longer come with a serial port installed, as most manufacturers have migrated to USB. The SignalLink uses voice operated keying (VOX) to key the transmitter. There are Rigblaster and BUXCOMM interfaces that also offer USB support, as well as standard serial port support, which requires a USB to Serial adapter for most modern computers. This creates a COM port that will signal your radio to transmit. The downside to the SignalLink is that it requires internal jumpers to be moved and reset when changing to different radios, whereas the Rigblaster and BUXCOMM interfaces do not require the manipulation of internal jumpers. Interfaces that use standard audio connectors will need to be connected to the computer microphone jack and speaker output jack.

To complete the install of the interface, you will need to either connect the interface cable to the radio’s DATA jack or, depending on the radio, you may need to connect it to the microphone jack and external speaker output of the radio. Connecting to the MIC jack and EXT speaker jack is typically only necessary on older radios that were not specifically designed for use on the digital modes. These older radios will still interface for digital; they just need to be connected differently. Most modern transceivers include a built-in connector that allows for seamless connection to digital interfaces. The big three Japanese radio manufacturers– ICOM, Kenwood, and Yaesu– all use a 6-pin mini-DIN connector. All three manufacturers use the same ISO manufacturing standard, so all the pin out assignments of the connector are the same. This means that the cable can be used on any of the big three’s radios that have the correct connector. The author uses the same cable for an ICOM 208H and a Kenwood TMV71A with no problems. Many modern transceivers even include built-in USB support. If your transceiver has a USB connector, then it does not need an external interface. Just download the appropriate USB drivers from the manufacturer, and then connect the radio to your computer using a standard USB cable. The computer will then recognize a COM port and USB audio CODEC for the transceiver, completely eliminating the need for any more hardware. It is a good idea to install ferrite chokes on the USB cable to reduce the possibility of radio frequency interference (RFI).

Once everything is interfaced, it’s time to get on the air. Remember that most transceivers are not 100% duty cycle at their full power rating. This means that they are not designed to be keyed to transmit 100% of the time at 100% power. The best practice is to keep the output power of your transceiver at its highest setting (typically 100 watts on an HF transceiver), but then use the audio slider adjustment menu on the computer to lower the audio output level until the output power on digital modes shows on your meter to be peaking at 25 to 50 watts. 50 watts is the maximum, and reliable communications can typically be maintained at 25 watts, with very little gained by increasing the power any higher on most modes. Once operating, you will find that FL-DIGI has many digital communications modes, the scope of which is beyond the intent of this article. A very good reference, comparing digital modes, can be found at wb8nut. The most important thing to remember when choosing a mode is that different modes have different advantages and disadvantages, and experimentation is the key to success. You will find some modes that have high throughput levels that do not perform well in noisy conditions, and you will find some modes that have lower throughput but work better in noisy conditions. Your choice of mode will be dictated by propagation conditions, noise levels, and available power. Your knowledge will increase as you train with the different modes.

Another digital mode that the author highly recommends is the WINLINK 2000 radio e-mail system, details of which can be found at WINLINK allows you to use the same equipment discussed above to remotely access e-mail gateways all over the world via HF radio. WINLINK utilizes software called RMS Express, which looks and acts like a standard e-mail client, such as Outlook Express. The difference is that instead of connecting directly to the Internet using a local connection, it uses a software modem called WINMOR, which is included in the RMS Express install. WINLINK allows you send and receive e-mail remotely, over thousands of miles, which has great utility as long as there is still Internet connectivity somewhere in the world. This e-mail will be delivered to any valid e-mail address, including non-WINLINK addresses. The author includes WINLINK in his personal family emergency communications plan, because it allows him not only to e-mail his family but even to send and receive cell phone SMS text messages to them, using e-mail to text gateways that can be found listed at The author recommends that readers download a copy of this list for use in the event that Internet connectivity is not available. Using an e-mail to text gateway allows messages to be sent both ways, so even when a non-Ham replies to your e-mail or text message, it will be delivered back to you as a WINLINK message.

There several other advantages to digital communications that are worthy of further discussion. As most preppers know, communications security (COMSEC) and operational security (OPSEC) are crucial. The problem with analog voice communications is that while they are easily established, they are also easily intercepted by anyone with a radio receiver capable of covering the frequency being used. In order for someone to receive your digital communications they must not only possess the equipment discussed above, but they must also possess the knowledge of the equipment and the knowledge to recognize what mode is being used.

While digital modes are not allowed to be encrypted under amateur radio Part 97 rules, digital modes by their very nature defeat the undetermined and unskilled listener. If you try to listen to a digital mode using just a radio receiver, all you will hear is unintelligible data sounds. For a message to be considered encrypted, it must be deliberately encoded in such a way so as to obscure the meaning of the message. The digital modes used in amateur radio are based on open protocols, so the message is not considered to be encrypted unless one was to encrypt the message text before sending it via the digital mode. Further, programs such as FL-DIGI, FL-MSG, and RMS Express contain compression protocols that make file size smaller, and hence it transmits faster. These programs also allow for the use of custom-made HTML forms that are not available as a part of the default software package. These forms can be written by anyone with knowledge of HTML coding and then distributed to only those that you see fit. Any standard Internet browser will open and display HTML files. Combined, these capabilities have the added benefit of defeating snoopers, because while it is possible to reverse engineer the message content to read it, this requires extensive knowledge of software coding that is beyond the capability of most listeners. (Think three-letter agencies here; they can read it.)

In a TEOTWAWKI situation, messages could be easily encrypted and transmitted via amateur radio digital modes using a software suite called KLEOPATRA, which uses very strong, highly secure GNUPG encryption. This encryption works by using a separate public and private encryption key. This allows users who have never met in person to exchange public keys openly, while maintaining their own private key and passphrase in order to send encrypted messages. The best indications are that GNUPG will defeat even the best equipped and determined listener, and even a brute force attack would take several years to be successful using a supercomputer. It is certainly possible that any of the three-letter agencies may have a backdoor into this encryption, but GNUPG was designed by the Germans, who are a very privacy-conscious people. In order to send an encrypted message via a digital mode, compose a plain text message in the Notepad program, and then save it on your computer. Then, open KLEOPATRA, select your recipients (you’ll need their public key to do this), then enter your pass phrase, and re-save the encrypted file. You can then send the encrypted Notepad file using the FL-DIGI and FL-AMP software, which will guarantee 100% correct reception of your highly encrypted message at its destination. I must point out that this method is highly illegal under normal circumstances. DO NOT DO THIS under normal circumstances, or you will be in serious trouble with a large fine. However, you can simulate the entire process to get acquainted with how to do it. Just don’t transmit it over the amateur bands. The author has used two complete digital communications setups using non-licensed MURS frequencies. The author has personally verified that the process listed above does work very reliably and would work fine on the amateur bands. My test was akin to what the Air Force does when they test a Minuteman 3 missile. It proves that the system works without actually “pushing the button”.

The author maintains several complete digital communications set ups, including one in a base station configuration and two in a portable configuration. These set ups consist of HF, VHF, and UHF capable radios. Power reserves are a concern for any prepper, but a digital set up can be run entirely off of a 12 VDC power system, if a laptop computer is employed. Different types of generator power, inverters, 12 VDC battery banks, and solar systems can all power a digital communications set up completely off grid. Digital systems can be as complex or as simple as needed. It can be as complex as multi-band capability using many different radios to cover the entire world, it can be a simple system comprised of two laptops, two interfaces, and two low-cost walkie-talkies to cover a small area. The author encourages the reader to explore the digital realm and to connect with other like-minded individuals using this technology. Find a local digital expert and learn from them. Be patient and work through the inevitable problems, and your skills will improve. Most importantly, communicate daily with the Prince of Peace– Christ Jesus!