4.7 Practice
OFF
Normally you would leave Practice mode switched OFF. However if you want to practice sending
CW, and see if the CW Decoder can decode you, then you can switch Practice mode to ON. In
practice mode, the radio does everything it normally would, except that it never sends any RF
power to the antenna!
During practice mode, a ‘P’ is shown in the display to the right of the frequency on the top row.
4.8 Sidetone frq
700
This NUMBER parameter allows you to change the Sidetone frequency if you wish. Sidetone is
the audio tone which is generated by the microcontroller on key-down and injected into the audio
signal path. Sidetone is ONLY an operator convenience to let you hear your keyed signal, and has
no impact at all on the transmitted RF amplitude or frequency.
It is strongly recommended to leave the Sidetone frequency set to the same frequency as the CW
Offset frequency in the VFO menu. Your ears will get used to recognising the 700Hz audio tone,
and it makes it then much easier to accurately tune to a station you hear transmitting on air, such
that his signal will also be at 700Hz audio in your receiver. When you hear him at 700Hz, he will
be in the middle (near, anyway) of your CW audio filter. When you transmit you will also be netted
accurately to his frequency. All being well, this should mean that your signal also ends up nicely in
his CW filter passband too. Then you can QSO!
The minimum sidetone frequency is 350Hz; below this, the system automatically uses 350Hz.
4.9 Sidetone vol
099
You can use this parameter to reduce the volume of the sidetone audio. Most people will find the
default setting of 99 too loud. So experiment with lower values until you find a sidetone audio level
which you find comfortable.
When you adjust the sidetone volume by turning the rotary encoder after selecting a digit, the QCX
will play the sidetone at the new volume briefly so that you can hear how it sounds and easily
adjust it to a comfortable volume.
The sidetone generation uses some subtle digital signal processing to superimpose a 700Hz tone
on top of an ultrasonic audio frequency (at 42kHz by default); this retains an average 50% duty
cycle and thereby allows variation of sidetone volume without altering the DC bias at the feedpoint
in the audio signal path; this is found to eliminate a “click” that occurs on Rx / Tx changeover and
is most prominent at lower volume settings. A consequence of this change is that the apparent
sidetone volume becomes lower, if you reduce the “Sidetone frq” setting far below the default
QCX operating manual, firmware 1.07, manual edit 0.03
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