Kelly, I don't see anyone else jumping in to answer, so I'll give it a shot
although somebody else may provide better information.
Powerline noise on VHF (diminishing as one goes lower in the HF bands)
generally indicates a "leak" along a high voltage (high "tension"; anywhere
from 4400kv to 115kv and higher) primary carrier line somewhere relatively
nearby although it might be one to several miles away. I suspect that if you
were to go up onto 2 meters, it would be even worse than on 6m. The RFI is
usually caused by an arc somewhere along the line at a splice or, in your
instance more likely at an insulator on a pole or tower. If it's at an
insulator, especially on a metal tower, higher atmospheric humidity will
enhance the degree of the shorted insulator. Beyond this, we're getting into
meteorology in which humidity, temperature, and dew point become involved and
the amount of atmospheric moisture available to create an insulator short
varies widely with geographic location. Here in west central Arizona where the
humidity is normally around 10%, we see high voltage RFI-creating insulator
shorts very ra
rely, but on the rare occasion when humidity goes up to, say, 50%, we see a
lot more RFI; those insulators which are marginal will then short out enough to
creat RFI. It'll vary from hour to hour as does the humidity and temperature.
How to track down a bad insulator on high tension lines? If one doesn't have a
handheld directional antenna (like in foxhunting) and portable VHF gear, the
next best thing might be to walk the line at night when the interference is
acting up and look for an arc along the line. Some on this group might have
better ideas and more sophisticated RFI-detection equipment, but I'm think more
along the lines of those of us who are bothered by RFI only on occasion.
Hope this helps a little.
73 de Fred K2FRD
At 8:13 AM -0700 6/4/06, Kelly Johnson wrote:
>What does it usually mean if powerline noise slowly increases from S0
>to about S6 in the middle of the hot day and goes back to S0 an hour
>or two before sunset? It seems to me that I remember hearing that
>certain types of causes tend to make it occur only when it is hot or
>only when it is dry/wet, etc. The noise appears to be worst on 6
>meters and decreases as frequency is decreased.
--
73 de Fred Stevens K2FRD, VO2FS
http://homepage.mac.com/k2frd/K2FRD.html
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