This project is to enable one to test the various band widths of a CW signal as a funtion of key speed, rise and fall time and keying waveform.  The picture below shows the schematic diagram.

CW Simulator Schematic.

The junper settings are shown below.

Jumper Settings.

The hardware is shown in the next picture.

CW Simulator Hardware.

The Arduino code is HERE.

The Arduino is powered by plugging it into a USB port.  The rest of the circuit is powered by a 9 volt battery.  The 9 volt battery is not used to power the Arduino because the Arduino draws too much current.
The basis of the circuit is a 14.05 crystal oscillator drives the L port od a double balanced mixer used as a modulator.  The Arduino generates the key speed, keying waveform, and rise and fall times of the keying waveform, and is applied to the modulator through an 8-bit R2R network to form an 8-bit DA converter.  The output of the modulator goes through a lowpass filter and 10-dB attenuator.  The output can then be connected to a receiver or spectrum analyzer.  The keying waveforms can be individually to the ris and fall edges.  The rise and fall times can, also, be selected individually.  The jumper settings picture shows all the options.  The wave shapes at 40 wpm and 5 ms rise time has been tuned to be very close to exact.  The other speeds and rise times are not as exact.

In order for this device to operate well, the output needs to be linear.  A triangle wave is generated to test this, and the results are shown below.

Linearity Test Showng both the Modulated Signal and the RF Signal.

Below are some keying examples:

Square Wave Keying

Linear Keying

RC Keying

Raised Cosine Keying

Sigmoid Keying

The Rise and Fall times and Wave Shape primarily control the CW bandwidth.  This can be seen below with a Raised Cosine shape at 40 wpm with the rise and fall times varied.  The Rise time is measured from 10% to 90% of the waveform as shown below.

5 ms Rise Time.

Raised Cosine at 40 wpm with 1.5 ms Rise and Fall Times.

Raised Cosine at 40 wpm with 3 ms Rise and Fall Times.

Raised Cosine at 40 wpm with 5 ms Rise and Fall Times.

Raised Cosine at 40 wpm with 8.5 ms Rise and Fall Times.

The pictures below illustrate how the Wave Shape can effect the CW Bandwidth.

Linear Wave Shape at 5 ms Rise and Fall Times.

RC Exponential Wave Shape at 5 ms Rise and Fall Times.

Square Wave Shape at 5 ms Rise and Fall Times.

In a real situation on a transceiver waterfall, the pictures below show the effects of Rise/Fall times and Keying Waveforms.  Each tic mark at the top is 1 kHz.

           
Rise/Fall Times                                       Keying Waveforms