Tag: morse

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Morse Sending Tutor Mock-up

I realised that now I’ve made a CW Sidetone Oscillator, a Morse Keyer and a Morse Decoder, I could make a useful tutor for testing my sent morse.

The trick of sending good morse is in the timing. Getting the inter-character and inter-word gaps the correct length is quite difficult especially at higher speeds. So a tutor to check this could be a big help.

Morse Sending Tutor Diagram

So I lashed this together using a breadboard to do the connections. 

IMG 0070

And tested it as seen in this video: Morse Tutor Demo.mov.

As you can see it’s very rough and ready. If I were to make a proper version I’d remove the WPM and tuning aid on the top line which aren’t necessary. It would fit into a small box quite easily.

It was fun to throw together!

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CW Sidetone Oscillator

My 40m transmitter doesn’t have any frills at all. It is CW only and so far I’ve been listening to its signal on the receiver that I’ve been using with it. This works fine as the transmitting aerial is completely separate from the receiving aerial and the transmitter power is only around one watt.

So I’ve added a sidetone oscillator to the transmitter so that I can hear what I’m sending for when I do proper transmit/receive switching with one aerial.

I looked at PIC-based and LM386-based solutions, but decided on the circuit in chapter 1 of “Experimental Methods in RF Design” by Hayward et al (EMRFD). The circuit is based on a 555 timer. It beats other circuits I looked at because it is simple to build, uses through-hole components and is plenty loud enough for my ageing ears. Although it’s a square wave oscillator it sounds fine. I may add an LPF as the harmonics are louder than the fundamental.

I didn’t have all the components specified in EMRFD so I substituted others that seem to work fine.

Here’s the circuit and layout as ‘designed’ in EAGLE.

Sidetone Board

Sidetone SchematicThe circuit works as follows. The morse key is attached to the JP1-KEY pin and when the key is keyed it grounds R2 making Q1 switch on. The 555 timer is configured as a multivibrator triggered through D1. The square wave output goes to JP2-HEADPHONE pin.

I will replace R7 with a trimmer pot as the current value makes the output too loud even for me.