Morse Sidetone Recordings

I am currently practicing Morse receiving and sending as part of the CWOps CW Academy Level 1 course. I have three radios each with their own keyers and sidetones. Each keyer is different. Here are some recordings of the sidetones as taken from the headphone sockets. The course is by video conference in the evening, so I have the radio I’m using patched into a field mixer / audio interface along with my headset. This allows the instructor and I to both hear my radio and my voice in our headsets. (I like to hear myself).

I have also recorded the radios through their internal speaker (or through the Soundcore Mini in the case of the MTR3B). The microphone (an early version of the Naiant X-X now superseded) was hung about a meter above the desk and seems to have picked up as much of my breathing and the key mechanism as it has the radio. Noises such as operator breathing, key sounds, squeaky chairs are not so obvious to the user of the radio, so a closer mic technique may be better.

Yaesu 897

This is my oldest radio. It showed some issues on SSB HF which I think were due to a weak battery causing supply voltage to drop too low. I tested it on CW into a dummy load up to 20W using a Software Defined Radio receiver to see what the transmitted signal looked like. All seemed fine.

I like the sidetone and the keyer on this radio. It is the one I have practiced most with for the course, which may be a reason to like it. Here it is into the headphone jack.

Yaesu 897 sidetone recorded from headphone jack
897’s internal speaker, recorded with omnidirectional microphone 1m above desk

Elecraft KX3

This is another quite easy radio to key. It is different to the 897 but not hard to get used to. The sound seems thinner. I wonder if it is purer. I’d have to look on a spectrum analyser to see. I note the fuller sound if I deliberately overdrive the input to the field mixer. This was the quietest output of the three, with gain on the mixer increased to normalise it for this recording. It has certainly been adequate into earbuds when operating portable.

Elecraft KX3 sidetone recorded from headphone jack

Elecraft replaced the speaker as part of the repair and service job they did for me. The new speaker looks quite different, more solid, and seems to perform a lot better. Here the monitor level is set to 40. Again this recorded 1m above the desk on an omni mic.

Elecraft KX3 internal speaker, recorded with omnidirectional microphone 1m above the desk


This radio gives a fixed output which is quite loud. The receive audio is mixed in and the whole lot compressed and bandpass filtered. This is the only radio of the test in which I was not able to turn down the receive noise. This has proven the hardest keyer to get used to, such that I tend to not try squeeze keying with it.

MTR3B recorded through headphone socket
MTR3B into Anker SoundCore Mini. Recorded with omnidirectional microphone 1m above the desk

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