User Manual

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Hz. The buttons are numbered (1 to 10) from left to right. The factory default
values can be restored at any time, by pressing the Restore default
settings button. Each modulation mode has a separate set of IF bandwidth
presets.
For the AM, AMN, FM3, FM6 and FMN demodulators, a supplementary
low-pass filter is introduced in the audio output path, to reduce harmonic
distortion generated in the demodulation process and improve the overall
signal-to-noise ratio under bad receiving conditions. This filter’s length is
adjustable under the Audio filter length parameter.
Finally, a noise-derived squelch is implemented for frequency modulation
modes, FM3, FM6 and FMN. The energy of the noise present above the
useful voice baseband is used as a signal presence indicator. The
user can modify the length of the high-pass filter separating that noise,
Squelch filter length. The squelch control appears on the demodulator
front panel when any of the FM modes is selected. This makes it possible to
adjust the noise threshold level at which the squelch will mute the audio.
Finally, all demodulated audio output is scaled up by an Audio gain factor.
The scaled audio signal level is further adjusted with the Volume control in
the demodulator main panel. However, when the Audio AGC is active, the
fixed Audio gain setting is ignored, and the software will automatically
adjust the audio level according to the AGC reference level setting.
If you are experiencing audio distortion when using the Audio AGC, this is
probably because the AGC reference level is set too high.
The attack and decay times for the three possible Audio AGC speeds (slow,
medium and fast) can be also configured, under AGC Speed Constants on
the left of the demodulator settings window: