DSP filters compared

Posted by Richard Newstead on 17th Apr 2019

In the lab we have an FT897 that we use for testing speech compressors. While it is largely similar to the FT817 (apart from the higher power) it does have audio DSP filtering. I wondered how this might compare to the filtering provided by WOLFWAVE. To test the two filters I used a broadband noise generator connected to the antenna input of the radio and fed the radio audio into Spectrum-lab software.

The screen photo below shows the response on the two filters overlaid on each other. The lilac trace is the FT897's filter and the yellow trace is the WOLFWAVE. The FT897 DSP is only moderate in performance with gently sloping skirts and some high frequency artefacts. By contrast the WOLFWAVE is closer to a perfect filter with a sharp cutoff and a clean trace. On the bands it sounds much tighter and altogether better than the FT897's filter. Right click on the image to open it in a new tab of you want to take a closer look.