Pulsed Noise Problem
Wes Hayward, w7zoi, 9oct2017  ...

For the past several months I have fought a
n intense local wideband noise source.   It extends from the AM broadcast band (and lower) up through the entire HF spectrum to 30 MHz.    I have not yet examined VHF, but expect it to be there too.      The noise is pulsed with a repetition period of around 2 seconds.      I first observed the noise when new neighbors appeared in the area.

The noise has been measured in the time domain with the following simple set up.
  The fan inverted Vee that serves as our usual antenna for 40 and 20 meters includes a common-mode-choke balun.   The feedline is attached to a transmatch that was tuned to the 40 meter band for these measurements.   The resulting signal is then applied to a Rigol DS1052E digital storage oscilloscope, DSO.   A 50 Ohm terminator is fixed to the DSO input.    The transmatch or a similar high pass filter was necessary to attenuate local AM broadcast signals.      The noise seen on the DSO is shown below.  

   Scope settings are presented at the bottom of the display.   The sweep is slow at 1 second per division, illustrating the 2 second period.    The 50 mV/div vertical sensitivity shows the signal strength.  Typical pulse length is around 300 mS, although this is not a constant.   The noise will come and go, teasing me to almost try to get on the air, only to be foiled a few minutes later.     The DSO was set for "peak detect, real time sampling, normal memory depth, sinX/X on, positive edge triggering, and either normal or single shot triggering.

The noise has a definite fine structure.   If the time base is changed, it becomes clear that the "on" periods in the above figure are actually a collection of fast, narrow pulses. The 7 MHz transmatch in the signal path produces ringing at that frequency.   Changing the transmatch tuning alters the ringing frequency.    Replacing the transmatch with a cascade of a 50 MHz low pass and a 2 MHz high pass allows observation of the faster pulses.   One such case is shown below.
   This shot with a 2  ┬ÁS/div time base was taken with the DSO set for single shot triggering.   Once the above display is in place, the time base can be further changed to observe the pulses in even greater detail.     Incidentally, the real power of a DSO becomes apparent when doing such measurements.

I confirmed that the noise was not coming from my own home by merely tuning all power off at the
main breaker panel .   Battery operated gear confirmed that the noise was still there, even with an unpowered house.   I wandered the neighborhood, finding the highest intensity at the house belonging to the new neighbor.   He was accommodating and we did some experiments.  Turning power off at his main breaker panel confirmed that the noise was generated in his house.   We then started with individual breakers in his his panel and quickly found the circuit that powered the source.   We then wandered the house, looking for the source.    We found areas where the signal was stronger, but were not able to isolate the source.     The home owner had other plans at that time and we have not been able to continue the experiments since then.    The plan is to try again, but to now begin unplugging various appliances within the household circuit area controlled by the selected breaker.   

Two measurement receivers have been used in these investigations.   One is a battery powered general coverage receiver, a Sony ICF-SW7600GR.    An internal whip antenna was used for HF probing.  The internal AM loop antenna was also effective.    The other tool used was an Elecraft KX2 HF transceiver with a 19 inch whip attached to the antenna port.     The "S-meter" was useful when using the KX2.

The neighbor has observed some of the problems, isolated from my observations.      One is noise when he has an audio system operating with local FM.   He has also complained that a light dimmer is making a lot of audible noise when set to mid range.   I urged him to change this ASAP.
 
I have experienced noise from another neighbor's touch lamp.    That noise was radiated from the lamp and the immediate wiring.  I was able to eliminate the noise by carefully positioning a rotary dipole antenna.    This was not effective with the newer noise, suggesting that the offending noise source is generating conductive EMI (electromagnetic interference), causing much of his house to radiate.    A directional antenna is then less effective.

If any of you reading this have experience with similar noise, I'd love to hear from you.   ([w7zoi] {@} [arrl] dot net, converted to the usual format.)   My present intuition suggests that we are seeing a poorly designed or defective battery charger.    The 2 second period prompts this thinking.    However, my experience with noise of this sort is severely limited.     Thanks ahead of time for any suggestions.