Minimum samples parameter: both conditions must be satisfied in order for an audio frequency
measurement to be completed. This parameter is discussed further in the Design section of this
manual in the Audio Frequency Analysis section. The default value of 480 should be fine for all
purposes.
Bearing in mind that there are 48,000 audio samples per second, a value of 480 specifies a
minimum 0.01 second audio measurement period. In other words, there will be 100 measurements
of the audio frequency, per second, in this default configuration. This is sufficient to ensure that
high audio frequencies are measured accurately. In the unlikely event that frequencies below
100Hz need to be measured, the “Minimum cycles” value (1) will ensure that a longer
measurement period is used, to measure one cycle.
Discard cycles
This parameter specifies the number of audio cycles (zero crossings) which are ignored, when
audio is first detected. The reason for this parameter is that in conjunction with the “Rise threshold”
parameter, it can be seen that the first audio cycle after the threshold is passed, is not a complete
cycle. The following zero crossing therefore needs to be discarded because its period
measurement will be too short. The default value of 1 should be fine for all purposes.
IQ Mode
When IQ mode is enabled, the raw I and Q channels from the ADC are fed to the USB soundcard
directly, without any demodulation. This is suitable for people wishing to experiment with using
QDX as an SDR front end, with PC SDR software to demodulate I and Q channels. Remember
that there is a 12kHz IF offset applied to the VFO.
IQ Mode is not suitable for use with WSJT-X and other Digi mode programs.
Japanese band limits
When this setting is enabled, QDX will refuse to go into transmit mode if the specified synthesis
frequency is outside the Japanese band limits as specified in the JARL bandplans document
https://www.jarl.org/English/6_Band_Plan/JapaneseAmateurBandplans20200421.pdf
. This setting is useful for
Japanese license regulations compliance.
CAT timeout enable
When this setting is enabled, which it is by default, there is a timeout on Transmit; if the timeout
elapses and QDX does not receive a CAT command requesting it to switch back to Receive, then
it will automatically switch back to Receive.
This feature needs to be disabled if using VOX.
CAT timeout (sec)
The duration of the CAT command timeout (see above), in seconds.
QDX operating manual; firmware 1_04
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