Spectrum display Magnify mode = Zoom FFT

There was a longstanding wish of many mcHF users to be able to see the signals in the spectrum or waterfall display with ore resolution. Clint has provided us with a 2x Magnification mode that doubles the resolution, but in reality the same resolution is used, but the points in the display are interpolated. The problem remained that it needs more processor power to calculate higher resolution FFTs in order to obtain more resolution. The solution is to use a technique that is described by Lyons (2011) as the ### Zoom FFT.

The Zoom FFT is used when fine-grained spectral resolution is needed within a small portion of a signal´s overall frequency bandwidth range (Lyons 2011). That is exactly the situation we face when we want to see a small part of the spectrum display of the mcHF, but with high resolution. The Zoom FFT helps us to perform this without having to calculate high order FFTs. It consists of the following components:

1. complex frequency conversion to baseband