Spectrum Window Function Select

Macro: SpectWind

This set of six radio buttons selects the window function to be applied when the Window button is active. When the button is not active, the effective function is often termed "rectangular", which simply means no window function at all.

Hann (often called Hanning) offers good resolution of spectral peaks and good rejection of sidelobe leakage "skirts" at low levels for input signals that don't have an integer number of cycles in the 1024-point FFT data set. A good choice for most uses.

Hamming (not to be confused with Hanning) provides finer resolution of spectral peaks than Hann, but poorer rejection of sidelobe skirts at low levels.

Blackman gives peak resolution that is not as fine as Hann, but the response shape flares out less at lower levels and rejection of sidelobes is better.

Blackman Exact and Blackman-Harris are fairly similar to each other, but are both included for compatibility with existing data sets or user preferences. The peak resolution is similar to the regular Blackman, but the response shape flares out even less at lower levels.

Flat Top has the broadest peak resolution, but the best amplitude accuracy of any window here. It has a fairly straight-sided response shape at high and middle levels, then flares out like the Hamming at lower levels with similarly poor sidelobe rejection. Use this to measure spectral peaks where interference from adjacent frequencies is not a problem. It is the window of choice for swept frequency response measurements.

Macro Notes:

SpectWind=Hann sets the Spectrum Window to Hann. Other values are Hamm (Hamming), Bkmn (Blackman), BkEx (Blackman Exact), BkHr (Blackman-Harris), and Flat (Flat Top).

See also Spectrum Control Dialog