[RFI] Power Line Noise

Kimberly Elmore cw_de_n5op at sbcglobal.net
Thu Feb 25 13:00:34 PST 2010

K3LR suggested that I submit this here because there are a lot of you that know a lot more about this than I do. So, here goes:

Recently, I've noticed some pretty severe, intermittent power linenoise at my QTH. It had previously been a marvelously quiet place for
radio, but over the past month or two, that has changed. I had it againthis morning and so decided to do some sleuthing.

I live E of Norman, OK, in the center of a section bordered by Robinson on the S side, 48th St on the W side, Rock Creek Rd on the N side and 60th St on the E side.
Both OG&E and OEC lines run down all roads. On Robinson (the S
side) the OG&E lines are on the S isde and the OEC lines are on the
N side. The OG&E lines run 35 kV -- I don't know what the OEC lines run. My neighborhood is served by OG&E and all wiring is under ground; step down transformers are above ground on concrete pads.

Here are the details: 

I cannot detect the noise on any band above 40 m, but it's clearly apparent on 40, 80 and 160 m. My Orion II noise blankers are ineffective on 40 m (both the software and hardware noise blankers) but are very effective on 80 and 160 m. Because I cannot hear it above 7 MHz, I'm pretty sure that the source is not emanating from a neighbor's house or from a nearby step-down transformer.

Using my K9AY loops, I can detect the noise when the loops favor either NE or SE, but not whenthey favor NW or SW. Thus, the source is either to my N or my E.

Using my 2 el 40 m beam, I found sharp nulls with the beam pointed either Nor S (probably nulls off of the sides), and less noise when the beam is
pointed W than when it is pointed E (~S9+25 dB pointed E, ~S9+15 dB pointed W). So, F/B ratio favors a source to my E.

I then got in my car, tuned my mobile rig to a quiet frequency in the aviation band (118.0 MHz) so that I could use the AM detector at VHF and started driving E along Robinson to 60th street. I heard nothing of substance along Robinson. I turned N and drove along 60th and found a
strong noise source. I double checked my traverse and found the same spot three different times. It was considerably weaker from across the road than it is next to the pole. There is a private drive going E from 60th street, away from the offending pole. Driving down it 100 feet diminishes the signal strength significantly. The ground wire for the pole appears intact at the base.  I am absolutely positive that I have identified the pole holding the faulty hardware. I could see nothing obviously loose, but the culprit is most certainly there.

The noise is intermittent: it starts and stops abruptly as the wind blows,though I can detect no obvious correlation to wind changes and the
starting and stopping of the noise. 

What now? Whom do I contact with my information?

Kim Elmore, N5OP

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