User Manual

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The front panel of the Professional Demodulator looks similar to the
standard one. Note in particular the added DSB and ISB modes, the
continuous IF filter bandwidth control, enhanced Audio AGC (the time
constants are user definable in the Setup window), and a row of IF
bandwidth preset buttons at the bottom. The numbers on top of the IF
bandwidth preset buttons indicate the associated bandwidth (in kHz). These
presets, too, are entirely user-definable.
To change the IF bandwidth, you can type the desired value (in Hz) directly
in the IF bandwidth editbox, or use the associated up/down buttons.
Do not overlook the small but very significant slider located between the
bandwidth up/down arrow buttons: It allows you to change the IF bandwidth
within a large range, by moving the slider cursor up and down, with a very
impressive effect:
In the real-time spectrum scope, the currently selected IF bandwidth is
indicated using a different background color. The portion of the real-time
signal spectrum falling within the IF bandwidth is shown in yellow.
Adjusting Demodulator Parameters
Each demodulation mode has its own associated set-up panel, accessible
under the Setup button (located under the CW mode button). By selecting
the mode either using the front panel or the tabs at top-right of the
demodulator set-up window, you can see and adjust the filter settings
applicable to the selected modes.
The meaning of each filter is best understood looking at the demodulator
structure (under the View demodulator structure button). The cut-off
frequencies and lengths of these filters can be adjusted and optimized by
the user, either by direct typing in the parameter or using the sliders.
Each filter length (i.e. the number of its taps), can be an odd number
between 3 and 255. The more taps, the better the filter characteristics, and
the better the performance of the receiver, but the computing task for the
CPU is harder. Therefore, while increasing the filter lengths, always watch
the CPU usage (shown at bottom left of the demodulator Setup window) in
order not to starve the operating system of CPU resources (80% is a good