A New Morse Speed Formula

We can use the Paris standard to develop a new formula for reading Morse Speed.  Although it’s very simple, I believe this is original to myself, as I’ve never seen it in print anywhere.

Assume you send the word PARIS 12 times in one minute at a constant speed.  Then you send 12 x 50 = 600 time elements in one minute.  This equates to 600/60 = ten elements in 1 second.

Now 10 elements in one second is the equivalent of 5 dots per second (with their inter-element spaces), or a dot frequency of 5 Hz.  So 12 words per minute, or wpm, equates to a 5 Hz dot frequency, and 2.4 wpm equates to a 1 Hz dot frequency.  You can now see that morse speed in wpm = 2.4 x dot frequency.  This leads to the all-important formula:

S = 2.4d, where S = speed in wpm (words per minute) and d = dot frequency in Hz. 

This is all that is needed to design a CW Speedo; if you can measure dot speed, you can calculate speed in wpm (assuming the rest of the elements are correctly formed).

It works best with a paddle, and can work with a bug key (which I never tried), but needs a steady hand to measure using a pump key.

The frequencies involved are very low, the range 1 wpm to 50 wpm producing a dot frequency of 0.4 Hz to 21.8 Hz.  Once the frequency is measured, the formula has to be applied.  To overcome this rather clumsy method, I designed a circuit which gave a reading directly in wpm on a moving coil meter calibrated either 0-30 or 0-50 wpm as required.  The paddle key is simply plugged into the circuit.  Details available from me on request.

Best regards and 73s,

Dave

G4AJY.