I used a stand alone oscilloscope as well as a software based audio oscilloscope to look at (analyze) the audio received in AM mode from an unknown RFI source that Jeff (W4DD) is trying to identify, and below are pictures showing the analysis.  For comparison I also included pictures of power line RFI that's arcing 2 times each half cycle that I captured using my laptop based SDR receiver which was also confirmed using a Radar Engineers Model 243.  All audio was captured using 20 KHz bandwidth per my recommendation.

Note:  I recently discovered that I could obtain results very similar to those obtained using a Radar Engineers Model 243 or an oscilloscope in the near field with appropriate antenna when looking at power line noise as long as I use a very wide bandwidth.  I had been trying to accomplish this for many years and recently discovered the key is the large bandwidth.  I actually prefer 25 KHz or wider but 20 KHz is not too bad.  Don Kirk (wd8dsb)

Webpage created and maintained by Don Kirk (wd8dsb).  Created November 26, 2025