PreppComm MMX Tri-Band CW Transceiver: A new hope for saving morse code from extinction?

Article by James Hannibal. Callsign KH2SR.

Have you ever wanted to communicate with other people using Morse code, but didn’t know where to start? The MMX Morse Code Transceiver from PreppComm can help you get on the air and start operating CW (continuous wave) without knowing a single character of Morse code!

The MMX is the successor to PreppComms first transceiver the DMX-40 single band QRP rig which came out a few years ago. The biggest evolution between the DMX-40 and the MMX is the addition of the 20m and 80m bands on top of the original 40m band on the DMX-40. There have also been some improvements in the receiver sensitivity as well.

CW Morse Code has a rich history in the world of ham radio communications. It has been in use for many decades by ham radio operators to communicate with each other around the world. However, with the rise of modern communication methods such as SSB and digital modes like FT8, the use of CW Morse Code has significantly declined over the last three decades.

Learning Morse code can be a daunting task that discourages many hams from attempting it. Busy ham radio operators may be interested but have little time for CW practice between work and family responsibilities. It can be difficult to choose between studying CW or enjoying the fun of playing ham radio on the air. By making it easy for new hams to immediately get on the air and start making CW QSO’s, the PreppComm MMX lets you start enjoying the fun Morse Code right away.

The MMX is a great solution for beginners who want to learn CW while making real QSOs on the air instead of spending hundreds of hours practicing Morse Code before having made a single CW contact. With its easy walkthrough setup guide, even a young inexperienced technician license holder can easily start learning Morse Code while making QSO’s. This makes it an ideal option for enthusiasts who want to try dabbling in operating CW and help keep the tradition of Morse Code communication alive.

The MMX is different from other software and hardware that claim to have this ability. Other options fall short when it comes to decoding weak signals, decoding though the noise, or when the other ham isn’t sending consistently. The MMX on the other hand seems to handle all these challenges much more effectively in comparison. However it’s still not nearly as good as the human ear at decoding really weak signals down near the noise floor.

The MMX has a built-in decoder that can translate Morse code for you, so you don’t need any additional hardware or computer. It also has an encoder that lets you type your message on the included USB keyboard instead of tapping it out via a morse code key. Its bright color-coded LED lights indicate tone, CW in, CW out, and lets you know when you have wandered out of your operating privileges. These simple LED indicators are a very effective feature in helping a beginner get on the air. Another great feature is the type-ahead buffer, which allows you to quickly correct what you’ve typed before it gets transmitted. The MMX also has 10 frequency memories, automatic capturing of sent callsigns, and various built-in micro programs and user-customizable micro programs. 

One of my favorite features of the MMX is its ability to be connected to an external ham radio with higher power output and more band options. This is done via audio cables and the keyer jack. You can  then operate the MMX as purely an encoder/decoder for your high power rig. I love this capability, being able to hook it to my Yaesu 991A or 891 is amazing and works great both in the shack or out in the field. Just be sure you have the MMX set in “External” mode before you begin transmitting. I prefer to keep a micro sized SMA dummy load connected any time I don’t have an antenna connected.

Additionally, the compact size and portability of the PreppComm MMX make it an excellent device for those who enjoy portable operations such as SOTA and POTA. I have personally operated the MMX portable on many occasions and was pleased with its compact size and how lightweight it felt in my pack. The MMX has a decently sturdy build but it doesn’t have any seals to protect it from the weather so I highly recommend investing in a waterproof protective case of some kind to store it in. I would like to see an improvement on it would be the ability for end users to do their own firmware updates instead of requiring that the MMX be shipped back to the manufacturer to be updated. However perhaps this is for the best considering the potential for a user to accidentally brick devices during firmware updates. I’d also like to see more utilization of the touch screen instead of the majority of the control inputs going though the keyboard.

PreppComm also offers a variety of high quality accessories that perfectly compliment the MMX for operating in the field. My favorite is the go bag kit that comes with a 18″ x 13″ x 6″ water resistant canvas backpack, camo waterproof backpack cover, 21 watt solar panel, 28,000 mah battery bank, -45 dB mylar-on-metal EMP bag, 3 meters LMR-100 coax, 40/20 Meter No-Tune End-Fed Antenna, ground stakes, stake marker flags, 30′ and 15′ paracord on spools with cord locks, throw weight, wire tags and clips, and Antenna Setup Guide, and Panasonic earphones.

The MMX Transceiver gives me hope that we may start to see an exponential increased adoption rate of CW Morse Code in the ham radio community worldwide and with any luck prolong the life of this highly efficient and effective mode of communication for many generations to come. With the help of the PreppComm, the MMX, and any future products like it, Morse Code communication has a bright future ahead.

Designed by Eric Anderson, callsign AF7YQ
Built in Sandpoint, Idaho USA

Price: $499.00

Manufacturer website:

Article by James Hannibal. Callsign KH2SR.


• Multi-band: up to three bands supported via a three-slot card cage on the motherboard. Auto-sensing and auto-selecting via sense/select hardware on the motherboard – any slot for any plug-in band board. Use the Frequency button on the Main screen to select which band card to use. Currently available bands are detected automatically and offered via the Frequency button. 80, 40, and 20 meter band boards are currently available.
• Advanced Direct Conversion SDR Receiver: with custom filter, balanced mixer, and low-noise preamp giving sensitivity ≈ 0.3µV, -118 dBm or better
• GUI: 3.5″ color touchscreen LCD
• Weight: 11 oz with protective lid
• Size: 3.8″ x 5.2″ x (1.3″ w/o lid, 2.25″ w/lid)
• Power Consumption, receive: 1.4/0.96 watt, LCD backlight ON/OFF
• 80 meter band: 3.5 MHz – 4.0 MHz. SWL range: 2.45 – 5.6 MHz
• 40 meter band: 7.0 MHz – 7.3 MHz. SWL range: 4.9 MHz – 10.22 MHz
• 20 meter band: 14 MHz – 14.35 MHz. SWL range: 9.8 MHz – 20.09 MHz
• 80M Power Output @ 13.8V: approx. 2 W, 350 ma (key down)
• 40M Power Output @ 13.8V: approx. 3 W, 500 ma (key down)
• 20M Power Output @ 13.8V: approx. 1.5W, 350 ma (key down)
• Key up power @ 13.8V: approx. 110 ma, 1.5 watts (LCD ON)


    •    Simple GUI for multi-band operation.  The Frequency Button is also the Band button!
    •    Unparalleled Decoder Capability in Noisy Environments:  With its unique signal processing algorithms, the Morse Code decoder outperforms all others.
    •    Type and Read in English:  Use the included QWERTY keyboard to type, while hearing outgoing and in incoming Morse Code, aiding in learning the code subconsciously.
    •    (Optional) Learn Morse Code:  The included Morse Code Key-In capability with built-in decoder testing aids in learning the Code.
    •    Automated Send/Receive Protocols:  Enter your call sign and other information for station setup.  Remote station call sign captures automatically.  All call and answer protocols are automatic – you only type your message.  Or change the protocol via built-in micro-program editor.
    •    Set your maximum comfortable typing speed:  While the MMX can send very fast, it’s best to limit speed so you don’t starve the transmitter.  A unique feature that maximizes the use of the type-ahead buffer in transmit mode calculates your comfortable typing speed automatically.
    •    Super Power Micro-programming System:  Besides simple automating common text segments, the micro-programming system allows control over the transmitter, enabling many advanced features.  12 micro-programs up to 60 characters each.

Additional Features:

• Captures station call signs automatically, so you don’t have to do it, or even remember the call sign for the required station ID’s. It’s done automatically for you!
• Protects you from transmitting on unlicensed frequencies within the operating band, as well as outside it
• Built-in single keystroke INFO micro-program transmits the standard information commonly shared (name, location, rig, antenna). This information is entered for the local station in setup, including call letters, from the Main Menu
• Built-in Calling micro-program automates General Call (Calling CQ) and Directed Call (calling a specific station).
• Built-in Answer micro-program automates Validate-Answer (ensure there is a 2-way communication when answering) and standard back-and-forth communications, with all station ID’s automated.
• Pop-Up Type-Ahead Buffer allows up to 76 characters to be typed and edited ahead of the transmitter. Prevents starving the transmitter.
• Comfortable Typing Speed Test allows the capture of your typing speed, to be used to control the transmitter maximum transmit speed. Editable by the user, as well.
• Transmit Speed Throttle prevents transmitter from outpacing your typing speed. We call this Intelligent Transmit Speed Control – the combination of this speed throttle, and the automatic control of speed as set by the remote station. The speed throttle provides a mechanism for measuring and applying your comfortable typing speed as a transmitter throttle, allowing you to keep ahead of the transmitter at all times.
• Ten Frequency Memories per band, with custom 9 character labels accessible from the Menu System or keyboard shortcut.
• Frequency Memory Editor allows the user multiple ways to specify a frequency, as well as a label for the defined frequency.
• Touchable Frequency Memory List, showing all 10 frequency memories for the current band, all in one place. Frequencies can be selected simply by touching their entries, or edited by touching the associated EDIT button. Frequency Memories List is accessible from the Main Menu, or via a keyboard shortcut.
• Extended Range Receiver tunes from 2.45 to 5.6 MHz on 80 meters, 4.9 MHz to 10.2 MHz on 40 meters, and 9.8 MHz to 20.09 MHz on 20 meters, if you have those bands available in your transceiver. These frequency ranges – well outside of but including the amateur radio bands -cover many shortwave bands, as well as 5.0 MHz and 10.0 MHz WWV atomic clock frequency stations.
• Receiver Incremental Tuning (RIT) after transmitting, allows user to make fine adjustments without changing transmit frequency.
• Twelve User-Defined Micro-Programs that can be either be often sent text or transmitter control, or a combination of transmitter control and text
• Powerful Micro-Program Language RPL (Rig Programming Language) allows many powerful functions to be implemented, allowing user redesign of the operation of the transceiver CALL and ANS functions, focus on contests, message station repeating a message at programmed intervals, and much more.
• Microprogram Editor allows full text edit of up to 60 characters per micro-program. Micro-program Help Screens directly available from the Editor.
• Touchable Micro-Program Lists: All micro-programs are listed on 3 screens, and can be executed by touch, or edited by touching the associated EDIT button. The Microprogram List screens can be accessed from the Main Menu or a shortcut key.
• Upgrade Existing Transceivers to Full Morse Code Capability by connecting to the AUDIO-IN and KEY-OUT connections and switching to External Mode. This eliminates the 40 meter band limitation of the DMX-40.
• Full Keyboard Control: 18+ keyboard commands plus 44 frequency memory and microprogram edit and execute keys provide full control of most functions from the keyboard
• Transmit Speed Automatically Set based on received frequency to match the other stations speed capability, and user speed throttle when local user typing speed is slower, for smooth communications
• Single Keystroke Default Transmit Speed for first outgoing call. Alternatively, a different value can be keyed in, and the value can be optionally set as the new default.
• Power Saving auto LCD Backlight Shut-Off after 3 minutes of no activity to conserve battery power. Single key restores backlight.
• Extensive Help Menus for microprogramming, and transmit and receive keyboard commands.
• User Accessible VFO Calibration via WWV Signal. Every MMX is factory calibrated to WWV to within 10 Hz, and thus should not require recalibration for at least several years.
• Large, Easy to Read color-coded LCD Text for incoming and outgoing text, transceiver status, and type-ahead buffer.

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