Topband: Shack wiring & noise

[Tom Rauch]

> It's very cold outside--about 0 degrees F.  When the blower on the shack
> furnace kicks on, my noise levels dropped enormously.  The noise is a "egg
> frying" hash type.  My noise is not bad.  S0 with the 500 Hz filters on.
> The improvement in noise can only be observed when the 1/2 horse motor is
> starting.  It will last for about 2-3 seconds.  Topband signals will pop
> right out of the noise and disappear once the blower was up to speed.
> Whatever is going on, I want that experience all the time, not for 3
seconds
> every few minutes.

Very large electric motors have a starting capacitor that switches in only
when the motor is at rest, and is initially activated. Most furnace and air
conditioning motors have a "run" capacitor of a few microfarads that is in
circuit all the time. Furnaces often have HV arcs that ignite fuel, so they
do not need to waste fuel with a pilot. This causes a tic or buzz when the
igniter runs.

I don't know what you have going on, but here is something I had happen
once.

I had a neighbor with a very trashy switching power supply. Although a line
filter in my shack didn't help, I COULD reduce the noise by putting a pair
of .01uF LINE UL/CSA RATED capacitors in a plug, and finding a "magic
outlet" in my house. The two capacitors went from each line wire to the
safety ground. You MUST use a UL/CSA rated flame resistant component in this
application!! Whatever you do, don't improvise or do anything foolish
because messing with power lines is a safety hazard!

By shorting the correct outlet for RF, I could minimize the RFI re-radiated
by my house wiring into my antennas. Other outlets did nothing at all, I had
to find one particular outlet.

This is a long shot Ford, and above all think through the problem! Don't
ever do anything unsafe with a power line, even a 120 volt line. I would
also make sure you have a good ground at the service entrance, and that the
telco system and CATV cables are all grounded to that same point.

I'm working on an additional noise page related to noise sources, and when
it is finished and up on the web I'll advise here.

73 Tom