How To Measure the 3dB Point of a Filter

If you have a handy signal generator and a scope you can manually plot a filter response.  Here's a video using a SIGLENT SDG2122X arbitrary waveform generator and an SDS2304X oscilloscope to find the 3dB point of an RF filter.  It's much easier, however, to use a spectrum analyzer with a built-in tracking generator that sweeps through a frequency range to plot the result automatically.  The video shows the manual results confirmed using an SSA3032X Spectrum Analyzer.

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