User's Manual

WiNRADiO G39DDC User’s Guide
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The notch filter is a band-stop filter which can be used to minimize the effects
of interference falling inside or near a received station’s spectrum. Each filter is
activated by pressing the associated Enable button. The center frequency and
the width can be adjusted using the appropriately named controls.
For both notch controls, the same usage rules apply as with the demodulator
bandwidth setting, i.e. the values can be changed by direct manual entry, or
selected from the drop-down list.
Another way of changing the notch filter parameters is by dragging the
stopband of the filter (a blue shaded area) with the mouse. The stopband
width can be adjusted by dragging the edges, while the centre frequency can
be changed by dragging the centre line, which makes it possible to
conveniently position the filter stopband over the interfering signal.
The Center button serves to relocate the notch filter stopband to the center of
the demodulator filter passband. This can be useful in situations when the
notch filter is hidden beyond the currently visible demodulator spectrum limits,
in particular when the spectrum is zoomed in.
The following picture shows a signal with strong interference in the passband
(the large peak right of center, at the cursor position).
In the resulting audio, typically there would be a strong buzzing sound. After
applying the notch filter, adjusting its center and bandwidth (by dragging the