If the noise blanking period is too short, then noise impulses will not be blanked effectively. On the
other hand, if the noise blanking period is too long, then it will impair the decoder’s ability to
decode high speed Morse. For example, 24wpm Morse has dits lasting 50 milliseconds.
5.2 Speed avg.
07
The duration of dits and dahs is measured in order to define a threshold at which to define a tone
burst as a dit or a dah, and whether to define no tone at all as an inter-symbol, inter-character or
inter-word gap. The measurement of this timing is implemented via an exponential moving
average, whose averaging duration is determined by this parameter (the weight of each new
measured symbol in the accumulated average).
If the exponential moving average is too fast (the parameter value is too low) then noise etc will
throw off the timing averages too easily. If the exponential moving average is too slow (the
parameter value is too high), then too many characters of the other station’s transmission will be
missed, while we try to adjust to the speed of his sending. This can be particularly offensive in
some contest or pileup situations where exchanges are very short.
5.3 Ampl. Avg.
60
The decoder maintains an amplitude threshold, which it uses to decide whether a tone is detected
or not. The level of this threshold must be varied automatically in order to cope with stations
having a wide range of different signal strengths. Other perils may include QSB (signal fading) of
the station you are listening to. The amplitude threshold is implemented via an exponential moving
average. The weighting of each new sample (every 4ms) added to the accumulated exponential
moving average value is the reciprocal of this parameter.
If the exponential moving average is too fast (the parameter value is too low) then noise etc will
too easily throw off the amplitude threshold and it may take time to recover to its proper level. If
the exponential moving average is too slow (the parameter value is too high), then it may take too
long to adjust to the received station’s amplitude, resulting in missed characters while the decoder
slowly adjusts itself. It would also be too slow to automatically respond to QSB (signal fading).
5.4 Enable Rx
ON
An experienced CW operator may well dislike the CW decoder scrolling across the display all the
time. With this setting you can switch “Enable RX decode” to OFF and the receiver decoding is
disabled.
QCX operating manual, firmware 1.07, manual edit 0.03
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