[Elecraft] Noise, RFI ?

[Phil Hystad]

Using my K3 I was trying to pick up a ZL2 station (New Zealand) around 18.08 MHz this morning (about 9:50 AM PST) when this huge noise blanketed everything out.  It was about 30/9 and absolutely solid across the spectrum shown on the P3.  Using my KPA500, I switched to the 20 meter band -- same noise, same level, same broadband impact.

I determined that the noise was from roughly 1400 KHz all the way up to 28.05 MHz.  All about 30/9.  About the time that I finished checking this full MF/HF spectrum of noise it switched off.

Then, it switched on, and stayed on for about 5 seconds, then off again.  I turned on my Icom R75.  The next time the noise came on I checked it with the R75 and the same noise, same 30/9 level, same broad across the bands.

Obviously man-made or under man control as it switched on and off and was on for various periods of time.  This noise seems to be close, like generated in the neighborhood someplace.

Anyone have ideas of the cause.  You noise experts (Jim?) should have ideas.  I was thinking maybe an arc welding machine but that is just a wild guess.  It sure seems to be something that can be switched on and off.  It is not periodic in that the on/off switching is at varying intervals.  The longest on period is about one minute, the shortest on period about 2 seconds.  And, it has been quiet for the last 10 minutes or so.

Thanks for your help.

73, phil, K7PEH