[Boatanchors] Wierd Line Noise Observation on 40 Last Night

[Freeberg, Scott (STP)]

I went down to the shack early last evening and turned on the Johnson Ranger 1, Viking Courier, 75A-4.  It was already tuned up to 40 cw from the weekend so I didn't re-tune.  The setup runs about 350 to 400 watts output.  I listened around the band, found someone calling CQ, then for the first time, briefly keyed the rig to make sure the SWR was OK (as I use a Viking KW Matchbox), and was then greeted by 20/S9 line noise.  I turned on the KWM-2A and could hear it on there as well.  I then shut off the Ranger/Courier/75-A-4 to see if the noise might be coming from them, but the noise was still there.  This same thing happened last weekend too.  40 was nice and quiet, I tune up, bam, line noise. 

I seem to recall observing this last fall when I got on 75 AM during the day.  Band is quiet enough, I get in on an AM QSO , running some mildly serious power, about 200 watts out with the Desk KW backdown all the way, and bam, line noise.  

The only correlation to anything is that it was day light out.  I don't seem to recall observing this late in the evening.  I'm not sure because I don't have that many data points.  It was still lite out last night, ditto on the weekend.  

I'm wondering if my signal is triggering the street light to try and start up while its still light out.  Its just a hunch because I don't have any other explaination.  Tonight I was thinking of testing with just the Ranger and its low power.  Then  switch in the Viking Courier at 400 watts out and see if the line noise starts up.

Does anyone have any insight into this?  Strange huh?

73, Scott WA9WFA