A few additional comments re power line noise:
You may find that a QTH that seems quiet with a simple, low antenna
becomes quite noisy when you put up a real contest antenna. For
example, my QTH is very quiet on a low tribander, but I get a lot of
power line noise from antennas that have vertical patterns optimised for
low angles. In addition to the daily and weather variations, this is
another way to run into unexpected difficulty with a new QTH.
Also, with regard to various power line voltages, there are two distinct
types of line noise, spark discharge and corona. You can see the
difference quite clearly by looking at the IF output of a receiver with
an oscilloscope, especially if you look ahead of the narrow filters.
Spark discharge has one or more distint spikes at the voltage peaks of
the line voltage. A discharge can begin with one spike, but as it gets
worse you can see up to 5 or 6 spikes at each voltage peak. This is
the discharge of the capacitance of a high resistance contact, and is
almost always caused by the pin-and-clevis joints in the multiple bell
insulators you see wherever the direction of the line is changing at a
pole. This can be fixed by getting the power utility to replace the
bell insulator string with a single-piece insulator called an Epoxilator.
Of course, it doesn't hurt to worry about the issues of loose hardware,
and the hairpin springs are worth it if you can get them to install them.
Very high voltage distribution lines, such as 230 kV, are another problem
altogether. They are prone to corona discharge, which instead of narrow
spikes looks on a scope like white noise modulated by a rectified 60 Hz
wave. You can't touch corona noise with a noise blanker, and it has a
different sound to it because of the strong 120 Hz component. Most utilties
are very reluctant to touch these high voltage lines, because they don't
want to take them off line for service. Corona can be caused by something
as simple as a small piece of wire resting on the line or a sharp metal
point where the line is held to one of the big insulators. Out local
utility washes the insulators once in a while, using a helicopter with
an insulated "diving board" that the hose operator sits out on (not my
idea of a great job!). But if you have corona, the only way you can
get it worked on is to convince the utility that the line has been
damaged (they worry about gunshots) and may fail, and that the noise
is a preliminary sign of failure. Good luck, it's better to avoid the
very high voltage lines even though they have a generally good reputation.
The problem with line noise is that it costs the utility nothing in the
way of lost power, so they aren't very motivated. Most are more
responsive to TVI complaints. Out local utility has a terrific line
noise technician, but he has a hard time getting any action once he has
identified the problems.
I agree with the opinion of several top contesters with whom I've discussed
noise problems: if you have line noise, you lose the bottom layer of
weak stations that you could otherwise be working for a real difference in
a contest score. The best locations in the world (EA8EA, PJ1B, for example)
are absolutely quiet, and the difference shows in their scores.
73 de Dave, W6QHS
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