Hi

Do you have a high voltage power line in the vicinity? 

The insulators on those lines have a finite life. As they degrade, eventually they start to “leak” (= arc). Once they do that, you have a really fine broadband RF source hooked into a giant antenna. Often not easy to find.

The good news is that if you *can* find it, the power company is pretty darn likely to fix it. Indeed, they just *might* be interested enough to come out with some fancy gear to spot the problem themselves. It’s been known to happen in the past ….. That arc is costing them money. 

Yes, that’s one of an unfortunately long list of possible sources. 

Bob

On Aug 26, 2024, at 11:47 PM, Larry Osborne <[email protected]> wrote:

I have a similar, but worse, problem. I retired several years ago and I finally got my ham license. I have played with HF since I was 12 (although I stopped transmitting illegally when I was 16 or so), and looked forward to finally being legal. One night I was aligning a Heathkit Mohican when suddenly the whole shebang was overrun with noise. I figured I had done something stupid and went to bed figuring I'd see what I had done wrong the next day.

But the noise was still there. My Kenwood had always shown noise at about the S3 or 4 level, which was bad but still usable. Now the noise pinned the needle. Same thing on my vintage sets and my Sangean portable. When we had the big ice storm and the power was off the noise went back down to S3.

There doesn't seem to be a source of the noise; I've tried to locate it. No luck; there's no null anywhere. It happened all of a sudden. It's power related (but that might mean it's caused by something being powered). I tried turning off the master circuit breaker for the house, hoping I had something causing it plugged in … no dice. I've tried phasing noise cancellers, directional antennas, magnetic antennas, all sorts of things. Very irritating. Everything from AM broadcast to 30 mHz is useless in my whole neighborhood.

Larry Osborne Ph.D. (Ret.)
   No longer an authority on anything
KI7UFC
+1 808.630.8176
     or via W.A.S.T.E. 
            



On Mon, Aug 26, 2024 at 1:28 PM Tim <[email protected]> wrote:
Didn't want to hijack the Code Wheel  thread...However:  Interesting RFI paper Steve - Thanks...

Just for fun I just tuned my HF receiver from 7.0 to 8.0 mc.  Located in Suburbia, low halfwave dipole, noise floor at quiet freqs about S2 at 1315 Local.
I counted 24 hashy, fairly broad noise sources in that band that showed above S4, there were many other weaker ones.  You can even see their presence on some remotely located SDR sites that were picked as to be "quiet".  You can watch them drift around in the waterfall tuning ranges...Probably local to the antenna.

Since I work 40 CW fairly often I find these things drift around and invariably land on that weak CW op I am trying to work. They then drift away after a minute or so.
Since our ((not)great) power utility power company fails pretty often around here I get a chance to scan the bands while the neighborhood is "out" using battery powered receivers - very quiet.  I did find a bad wall wart in my own house that way - it powered a USB gizmo.  Replaced, S9 noise gone from that one; gave it a new attitude with a ball peen hammer...

Anyway my $ 0.02
Thanks, Tim
N6CC
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