That ages old method of communication Morse Code is alive and kicking on the HF radio bands giving us good strong signals to decode when all other transmissions are swamped or just not there. The simplicity of Morse code has an advantage over other radio signals when dealing with the huge amount of interference that the HF bands can suffer at times making it the ultimate backup method for emergency communications.
You don’t have to learn Morse code to view the information sent in broadcasts as there are numerous free pieces of software you can download easily from the internet.
The Morse code decoders are often bundled into a whole software package that will let you decode so many of the different digital signals from around the world that can usually be picked up with a modest shortwave radio setup.
In this article we are going to show you how to decode Morse Code using a program called Multipsk and touch on some of the other features this software has to offer. Once you have an understanding of how listening to these types of signals works you may like to try decoding some of the other interesting signals found on the HF radio bands.
For a free download of Multipsk (9.9 MB) and installation instructions CLICK HERE
Please note that Multipsk is designed to work with operating system versions windows 95 to Windows 7
When you first start the program you will be shown an options panel, pressing the big RX/TX Screen button will take you to the main program (don’t worry about the setup options at the moment as we will get to them later).
If all has gone right with the install and you have started Multipsk the main receive window will show on your computer monitor, there are a lot of buttons on the main screen as well as a lot of functions in the drop down menus but don’t worry as the actual job of decoding Morse code is easy enough. Feel free to have a good look around the programs many options, this website will still be here when you have run out of buttons to press 🙂
Connecting Your Shortwave Receiver to a Computer
This whole program works by sampling the audio from your shortwave receiver and converting all the unique sounds into text and pictures we can read. To do this a simple connection between the radio audio output and the computers microphone socket is needed.
If your shortwave radio has a stereo headphone socket then its just a matter of buying or making a long enough cable with a stereo 3.5mm jack plug at either end.
Some shortwave radios only have a mono output that will just send audio to one side of a pair of headphones and these will require a special lead to make this whole setup work. By connecting both left and right sides of the stereo 3.5mm jack plug lead that comes from your computer to the one output on a mono 3.5mm jack plug you will be tricking your computer into thinking it is listening to stereo audio (see diagram below).
Using the Multipsk Interface to Decode Morse Code
On the right side of the panel at the top of the screen you will see a big section full of buttons all marked with various letters, these are all the different signals that this piece of software will decode.
To start decoding Morse code you need to push the button marked “CW” (see diagram below).
Now its time to switch on your shortwave receiver and go hunting for some Morse code signals to decode. There are many places in the HF radio spectrum where you are almost guaranteed to pick up some Morse code but this can change depending on the time of day or night.
A good place to start during the day is 14.000 to 14.100 MHz or if listening at night try 7.000 MHz to 7.050 MHz. Remember to switch your radios receive mode to CW or SSB to improve the audio of the Morse signal.
The picture below is how the Multipsk program looks when it is listening to the audio from your shortwave radio with the actual Morse signal we want to decode shown by the red line in the waterfall. Tune your shortwave radio so that the red line is as close to the center of the waterfall as possible then left click on it with your mouse. This will put the signal directly between the two blue lines and allow multipsk to start decoding it.
If the waterfall is still black then Mulitpsk is not getting any sound, increasing the volume on your shortwave radio will give the program more audio to work with or adjust the computers microphone input levels via the standard windows operating system audio controls.
It is common to have more than a few signals so close to each other that Mulitpsk will show a few red lines in the waterfall. To decode the other signal you don’t have to re-tune the shortwave radio just click on the red line you want and the software will start to decode that individual signal while ignoring everything else.
Reading the Decoded Morse Code
As the Multipsk software starts to make sense of the Morse audio from your receiver it will display each letter one at a time in the left of the big white panel below the waterfall (see picture below).
Remember that the software relies on sound to decide which letter should be printed and if the Morse signal is weak or distorted by other radio interference it can cause errors with the decoding resulting in the wrong letters being printed .
The waterfall feature is used in the same way to decode all the signals that this software can handle and makes things easier because the strength of the signal is represented by how thick the red line is. With some quick practice it is very easy to master this feature and instantly know if the radio signal is strong enough to decode properly.
So Much More than Morse Code!
As you can see from the decoder function panel there are a lot of data modes floating around on the HF bands and after getting to grips with Morse maybe you would like to try some of the other features Multipsk has to offer.
For full details on any of the data modes including the best places to find them you can type their name into any internet search engine and we recommend a data mode called SSTV as a good place to start.
Morse Key photo courtesy Wikipedia