Morse Code and RTTY Keyer

Mortty is a Do-It-Yourself construction project that provides a miniature enclosure and a computing platform for K0SM’s TinyFSK RTTY Keyer software or K3NG’s CW Keyer software. It optionally can be configured to run W1HKJ’s nanoIO software using fldigi.

Unlike the full-featured – and more expensive – hardware solutions for CW and RTTY keying that are widely available to amateurs, Mortty is an inexpensive minimalist solution that depends upon the configuration and control features incorporated in popular logging and control programs. This tiny box measures only 2 inches long and 1 inch square (50mm by 25mm). Mortty has two input connectors (a microUSB jack to connect a computer and a 3.5mm jack to connect a CW paddle) and one output connector (a 3.5mm jack that provides PTT, CW and FSK signals to your transceiver).

Designed by N8AR and K8UT, Mortty is available as a complete parts kit, or you can use this guide to build your own from “scratch.”


Key Features

  • Inexpensive, off-the-shelf, readily available components (except for the Mortty board itself)
  • Small, portable, USB-powered
  • Rugged RFI-resistant metal enclosure
  • CW Keyer emulates the widely supported Winkeyer protocol
  • RTTY FSK keying via widely supported TinyFSK protocol
  • Optional Dual-Mode Sketch CW and RTTY operation using nanoIO and fldigi
  • Construction requires only common hamshack tools

Setting Expectations

    • What’s missing from this miniature design?
      • For CW – No speed potentiometer, no macro pushbuttons, no monitor speaker
    • Standard Mortty v3 Single-Mode Sketch configuration, CW or FSK – but not both?
      • Mortty operates either CW Keyer by K3NG or TinyFSK by K0SM
      • Switching between modes involves: closing the logging program, unplugging the Mortty output cable, launching the Arduino IDE, uploading the desired sketch (CW or RTTY); re-inserting the output cable
        • Elapsed time for switching modes – about one minute
        • Maybe you should build two Morttys? 😉
    • Optional Mortty v3 Dual-Mode Sketch configuration using nanoIO and fldigi – both CW and FSK
      • Optional assembly configuration provides for separate PTT, CW and RTTY outputs (three wires)
      • Requires using nanoIO by W1HJK with fldigi for CW and RTTY operation
      • Switching between modes accomplished via menu selections in fldigi
    • Degree of mechanical difficulty – low (if you use the 3D printed plastic end caps)
      • The Mortty board fits very tight in the metal enclosure. You may need a file or sandpaper to adjust the Mortty board for a snug fit in the case
      • If you decide to use the metal end caps, you will need to make five holes in the enclosure end caps
        • Use this documentation or the plastic end caps as a drill guide
        • Drill four round holes for paddle input, keyed output, and two LEDs
        • Drill / notch / file one oblong hole for the Arduino Nano USB connector
    • Degree of soldering difficulty – medium
      • To achieve Mortty’s miniaturization, the components are tightly packed on the circuit board
      • There is only one surface mount part, the paddle jack. Its solder pads are as large as standard circuit board components and will be no more difficult than soldering the other components
      • You will need some type of circuit board holder and parts stabilizer to assist in soldering parts to the small Mortty board (small vice, tweezers, hemostats?)
    • Degree of computer expertise – low
      • No programming required
      • The are many excellent resources on the Internet to assist you in loading the proper drivers for the Arduino Nano and uploading the desired sketch onto the board
      • Based on your PayPal order, we will preload the Arduino Nano with your desired sketch (TinyFSK, CW Keyer or nanoIO)

Mortty v3 in its final assembly stage

Order Info

The Mortty CW and RTTY Keyer Kit includes all of the items listed in the Assembly Manual Parts List page: the Arduino Nano, the case, the USB cable, the Mortty printed circuit board, and all components to be installed on the Mortty board. You will need a cable to connect to your radio and the tools listed in the Mortty – Assembly manual. Everything else is included in the kit.

Prefer an Assembled Mortty? Jim W5LA will sell, build, test and ship an assembled Mortty CW or RTTY keyer for $45 within the CONUS. Contact Jim at at for details.

IMPORTANT: As a convenience for first-time Arduino users, we pre-load your preferred mode on the Arduino Nano. Please purchase the CW, RTTY, and/or nanoIO versions of the Mortty kit (or kitS – 2 RTTY? 2 CW? one of each?). Of course, you can always replace the installed sketch later using the Arduino IDE.

Step 1: Shipping

Mortty kits and shipping information. You MUST include  one shipping method per package (not per kit).  Order multiple kits and pay only one flat-rate shipping fee.


Priority Domestic (US) Shipping = $7.90: Add one (1) shipping fee to each package


International (non-US) Shipping = $35.00: USPS Flat-Rate is the best/cheapest option at $35.{ugh!}

IMPORTANT! – You MUST purchase either Domestic or International shipping. Any Mortty orders that do not include a shipping fee will be held until shipping has been added.


Step 2: Product Selection

Select one or more of any combination of the following products. The Mortty developers will pre-load your sketch selections on the Arduino Nano(s).

Mortty CW kit price = $18.00 (US)


Mortty RTTY kit price = $18.00 (US)


Mortty nanoIO kit price = $18.00 (US)




Bulk Purchases

The following free (or cheap) shipping options are offered as an incentive to bulk purchasers. Consider using Mortty purchases and solder sessions as Special Events for your radio club.

USPS PACKAGING LIMITS: 3 Mortty kits fit into a USPS Small Flat Rate box; 15 in a Medium Flat Rate box; and 30 in a Large Flat Rate box.

For CONUS purchases of 10 or more kits, we will waive the shipping costs for that shipment. To order such a package, simply skip Step #1 on the Order Info page and in Step #2 select which combination of kits ( CW, RTTY, nanIO ) you want to purchase. To keep us from losing too much money to the USPS on shipping fees, please try and combine your purchases into “one large purchase on one day” rather than a few “just-over 15 kit purchases over several days.”

For INTERNATIONAL purchases of 10 or more kits, we regret that we must charge a shipping fee for every order, regardless of kit quantity. The current International USPS fees to most countries are $35/Small, $69/Medium and $90/Large. To qualify for a bulk shipping discount, you must order enough Mortty kits to completely fill the USPS box – 15 kits (Medium box), or 30 kits (Large box). On such an order select the International Shipping fee of $35 in Step #1 and in Step #2 select which combination of kits ( CW, RTTY, nanIO ) you want to purchase. Your order of 15 kits (medium box) or 30 kits (large box) will only cost you $35 for a Small Flat Rate box.



Close-up view of an assembled Mortty v3 circuit board with its 22 components

VERY IMPORTANT: The developers use some creative assembly tricks to squeeze all of Mortty’s features into this small enclosure. Please read and carefully follow the kit instructions in the sequence presented in the manual.

Mortty v3 assembly instructions can be found on the Downloads page HERE

The final version of the previous Mortty v2 assembly instructions is also available on the Downloads page

Mortty v3 kit prior to assembly

In addition to the Assembly Manual, the MP4 Video on the Mortty Downloads page describes the steps necessary to Connect, Download, Install, Compile, and Upload the software associated with Mortty.

The website links referenced in the video:

CH341G driver:
K0SM TinyFSK Sketch:
K3NG CW Keyer Sketch :
W1HKJ nanoIO Keyer Sketch:
Arduino IDE Program:


If you have problems assembling or using Mortty, the developers suggest that you look for answers on the Mortty reflector. You do not need to register, or login, or even have an account to search for a solution to your problem. (Although you will need to register if you want to post a new question.) can be found HERE.

The developers:
     Steve N8AR and Larry K8UT

Mortty – Schematic Diagram

Crisper image can be found on the Downloads page  HERE


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