02/07/2020

The OST Morse Box

OST is the local UBA amateur radio club in the city of Ostend, Belgium.
We have a small group of people that hold a weekly CW practice session on the local club frequency in the 2m band.
Some years ago (in 2018) I had the idea to build a Morse Box, to be able to have 'Tone CW' practice and QSO's on the 2m band, using FM mode.
I started a breadboard prototype with some info from the internet. Many such projects exist on the internet, from the very crude NE555 code practice oscillators, followed by a LPF to have 'some kind of a sine wave' ... but I wanted something better!
So I found a good circuit with a twin-T network, and finally got a working prototype.
I could connect the original microphone and I could select PHONE or CW with a switch.
It had a built-in straight key (the 'on hook' switch from an old telephone).
Later, I even added a touch paddle circuit with an Arduino Nano, what a luxury! 
This was the ugly beast.

It did work ... but I couldn't expect any of our club members to copy this thing.
The project was put aside and I lost interest for a while ...
In comes Gilbert!
Gilbert, ONL12523, is one of our SWL members, with a great interest in homebrew and programming, and he accepted my challenge to design a printed circuit board for the project. This was in the midst of the Covid-19 lockdown, so what better to do when confined to your home? 
But Gilbert looked at my design ... and saw that is was 'not good'. This could be made much better and more efficient when most of the functions were integrated in one small Arduino Nano. To make a long story short ... read below what he came up with, we proudly present: 
THE OST MORSE BOX!
The OST Morse Box is a versatile circuit that you can fit between the microphone and the microphone input of any transceiver. It was mainly designed for use with a VHF/UHF transceiver, but can be used for many other purposes.
The main goal is to be able to hold CW practice sessions on the 2m or 70cm band, where the students themselves can reply to the teacher in FM-modulated CW.
Another use is to make a few practice QSO's in a safe environment, before "throwing yourself" on the HF bands ...
In addition, the circuit contains a number of extra features, making this a very interesting club-building project.
By using an inexpensive Arduino Nano the following functions are available:

  • DDS Tone-Generator in software, for a perfectly pure sine wave 
  • Microphone is switched off while transmitting CW to avoid disturbing background noise
  • Automatic activation of the transceiver PTT
  • Adjustable DELAY for the PTT, from 0.5 ... 10 seconds
  • Variable CW speed of 10 ... 35 words per minute (WPM)
  • OLED display to read the set parameters and texts
  • Keying with Straight Key, Paddle or a built-in Touch Paddle!
  • Paddle polarity settable to NORMAL / REVERSE
  • Built-in "Keep Alive" circuit for use with a Power Bank
  • Adaptable to all existing transceivers, using the appropriate microphone plugs. The basic model is based on the widely distributed RJ-45 connectors
  • Power via the USB connection of the Arduino, via the microphone jack or from an external power supply
  • Use as a separate electronic keyer for transceivers without a built-in keyer
  • Random CW generator, display characters in the serial monitor and on the OLED display.
  • Beacon function, can also be used as a memory keyer (1 memory of 80 characters).
  • Additional functions can be set via AT commands via the serial monitor
  • Entering and transmitting text via the serial monitor
  • Windows program for controlling the OST Morse Box (then no need for the Arduino IDE)
  • Built-in TEST function for touch paddle


There is 32 page manual in DUTCH and ENGLISH, which was my input to the project.
It describes all functions and detailed building instructions, from building a very basic circuit to the full option Morse Box.
All files needed for making the PCB are on github (see link at the bottom). Make it yourself, order it from a local manufacturer, or order them cheaply in China (send me a mail for more info). You can also change the PCB to your liking, it was developed with the free edition of DipTrace (https://diptrace.com/). You may want to make the holes for the resistors a bit larger, and modify the PCB for the type of RELAY that you have.
UPDATE: the PCB layout has been modified for an OMRON relay, which should be more easy to source.
If you or your club make one or more of these PCB's, please send me a mail, we would love to hear from you: how many were built, were you succesful, what did like or dislike?
We also would like to keep track of how many of these Morse Boxes were built.
Send us a picture of what you made!
Versatility: not all options are mandatory, those who wish to do so, can partially fill the PCB to obtain only the desired functions. This is clearly indicated in the construction manual.
This is what the full option PCB looks like. External components are an OLED display, speaker, touch paddle contacts, LED's and some buttons and switches.
And your own straight key or paddle of course!

Putting it in a box is also up to you, we have no fitting cabinets in mind. If you find one that fits, let us know.

UPDATE: Gilbert has finished making a homebrew cabinet that looks really nice, see this post here.

Good luck in building, and have fun using the OST Morse Box!
All documentation is here on github: https://github.com/on7dq/OST-Morse-Box

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