[CQ-Contest] Power Line Interference

[Garry & Yelena]

tgstewart at pepco.com wrote:
> > This conversation should probably be moved to the rfi reflector..

Perhaps, Ty, but noise affects contesters almost as much as
DXers--especially if it is severe. (I have moved some of your comments
around to address them efficiently.)

> It's highly unlikely that the tree limbs were the actual cause of the
> interference.  It's more likely they were causing movement in some other
> loose hardware on a nearby pole.

> Loose hardware causes the vast majority of interference problems on local
> distributions.

The last statement is generally true, but I disagree with the first one.
If the branch lays across both primaries, it will conduct. It will
likely arc to the branch at at least one of the conductors, and the arc
will certainly radiate--intensely--using the conductors as an antenna.
It can also burn through the conductor, causing an outage with live
wires on the ground. I had just such a situation here last year: I heard
the arc, correctly decided its origin and direction, and resolved to
look for it the next morning. Before morning came, the wire had failed,
and we lost power for 10 hours.
> 
> One thing to keep in mind for location purposes is that the higher you go
> in frequency, the less distance the noise will propagate along the wires,
> so using a 2 meter AM or SSB radio to locate noise is much better than 10
> meters or lower (assuming that it's also creating noise on VHF...which is
> normally the case).

Yes, and the higher you can go, the better. Hardware-arc noise usually
decreases monotonically with frequency, up to 500 MHz and more, so the
higher you can listen, the closer you can pinpoint it, finally finding
the exact pole. H/T's with AM capability are better for this than FM.
Start on the highest band on which you can hear the noise, and go higher
as you get closer.

If the noise you hear does NOT decrease monotonically, but is peaky, or
rolls off in the low HF range, it is probably NOT pole hardware, but
consumer junk within neighbors' homes, like dimmers, touch-lamps,
rectifying connections, etc. 
-- 
Garry Shapiro, NI6T
160 meters: not a band, but an obsession


--
CQ-Contest on WWW:        http://www.contesting.com/_cq-contest/
Administrative requests:  cq-contest-REQUEST at contesting.com