But what is an FFT window and what is it doing? The principle is very simple. Here you can choose a number of FFT windows. In my old spectrum analyzer program in Visual Basic, no FFT window was used (no FFT window is also called Rectangular window). The function of the diodes is to avoid damage to the input of the soundcard by limiting strong signals. For small signals, you can decrease the value of R1 to 10k or 1k. You can make a simple probe with a 1M ohm impedance by yourself. You can decrease the value of R1 for small signals The difference between the shown trace and the stored trace is the side band suppression.Īnd if you do have a simple direct conversion receiver without automatic gain control, then you can see how much a signal varies due to for example fading. Set the trace again to Max hold and slowly tune the frequency of the RF generator over the suppressed side band. Reset the trace by setting it to Normal for a moment. Set the trace to Max hold and slowly tune the frequency of the RF generator over the wanted side band. You can also measure the side band suppression. In this way, you can adjust a crystal filter. And this average noise level corresponds with the audio characteristic. The Average function shows an average noise level. But you can get already quite a good impression by setting the trace to Average and receiving noise via the antenna. And you will see the audio characteristic appear. Set the trace to Max hold and slowly tune the frequency of the RF generator over the reception frequency. With such an audio spectrum analyzer, you can measure for example the audio characteristic of your CW or SSB filter of your receiver. This audio spectrum analyzer does have a correct dB scale. Audio spectrum analyzer with soundcard and software written in Python AUDIO SPECTRUM ANALYZER WITH SOUNDCARD AND SOFTWARE WRITTEN IN PYTHONĪUDIO SPECTRUM ANALYZER WITH SOUNDCARD AND
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