John Salmi, KB1MGI, writes on the PART of Westford mailing list:
I have had a S-9+ power line noise on my VHF beams on 2 meters and 6 meters along with my HF vertical antenna during the dry spells this spring and summer. When it rained the noise reduced or stopped all together. I traced it down to a pole 200 feet from my QTH.
I called National Grid a week or so ago about the issue. This morning a National Grid Senior Engineer from the Engineering Laboratory NE Lab & Testing services from Worcester stopped by. The first thing he said was, I wish it did not rain this morning.
I invited him into the shack and there was no noise. He said he went to the pole in question and could not pick up the noise, either.
He was going to send out a crew to check the connections and replace fuses, etc. He said they run into these issues from hams and knows what causes the noise on the radios.
I got his card and will call him in two weeks to see if the noise is gone.