700Hz. Therefore in version 1.02b the sidetone volume setting was increased from 2 to 3 digits. If
low sidetone frequencies are your preference, and if you find the sidetone too quiet, you can try
increasing the volume setting. There is a maximum which is given by the formula
166,666 / SidetoneFrequency – 2
If you set the sidetone volume louder than this maximum value, the system will automatically limit
the volume to the maximum value.
4.10 Strght mode
Both
Available settings are “tip”, “ring” and “both”. This controls the action of a key plugged into the key
jack during Straight Key mode only. If a 3.5mm mono plug was used with the QCX+, the longer
ground barrel shorted the ring to ground causing continuous keying. This configuration menu is the
solution to that problem. If you are using a mono 3.5mm plug with your straight key, then set this
configuration to “Tip” so that the ring connection (available only on stereo plugs) is ignored.
4.12
Decoder menu
The Decoder menu contains a number of configuration parameters relating to the CW decoder,
which are described below. Some of these parameters control some aspects of the decoder
behaviour. Some constructors may find it interesting to experiment with these settings and see if
you can improve the performance of the CW decoder in your specific circumstances. For example,
some stations may experience more noise interference than others, depending on your location
etc.
Note that the Decoder is able to decode the Morse prosign symbols AR, KN and SK/VA. When
shown in the decoded text section of the display, they appear as two characters, for example AR.
When using the keyer to enter text into message menus, the two characters are prefixed by the _
character to indicate to the QCX that when replaying the message, the following two characters
should be strung together without any gap.
5.1 Noise blnk.
10
This parameter defines the duration of the noise blanker in milliseconds. The microcontroller’s 10-
bit ADC samples audio at 12.019 samples per second. 48 samples are analysed by an
implementation of the Goertzel algorithm (kind of a single bucket of a Fourier Transform), which
results in a digital filter bandwidth of 250Hz. In other words, it results in a measurement of the
amplitude 250 times per second, i.e. once every 4 milliseconds. The amplitude is analysed by
logic which compares it to a threshold amplitude to decide if a tone has been detected or not.
Impulse noise that generates shorter pulses than the noise blanker parameter, is ignored.
QCX operating manual, firmware 1.07, manual edit 0.03
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