S E T U P F O R M
C H A P T E R 4
Figure 93 shows the effect of using various windows with a 1kHz DSB filter. The effect is most obvious
in the stop band attenuation of the filter, where the Rectangular Window (Black) shows the worst
result. In this case, the Blackman-Harris Window (Red) is obviously superior.
Figure 94 displays a 25Hz CW filter with a Hanning and a Blackman-Harris window. It is clear that the
Hanning window offers a narrower passband at the cost of a higher stop band. Blackman-Harris offers
a much improved stop band, but at the cost of a slightly wider passband. In almost all cases Blackman-
Harris will be preferred, except possibly for weak CW signals, where dynamic range is much less
important than a narrower passband.
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2003-2008 FlexRadio Systems
Figure 93: Effect of Various Windows: Rectangle (Black), Welch (Violet), Bartlett (Blue),
Hanning (Green), Blackman 3 (Orange) and Blackman-Harris (Red)
Figure 94: 25Hz CW Filter with Hanning (Red) and Blackman-Harris (Blue) Windows