But the frequency selectivity was interesting. Of course, we civilians
didn't have wideband receivers in those days, or means of visualizing
signals over a frequency domain, but this was nothing like the ordinary
sound of arcing that we are all too familiar with. The noise was
limited to two small segments, and in each was characterized by a sharp
cutoff at the high end and a gradual tapered profile going lower. The
mystery continues.
73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000
On 9/15/2012 9:08 AM, K1TTT wrote:
At least some of the old 'silent' switches had some kind of grease in them
to muffle the contact noise, perhaps it degraded, got some moisture in it,
or a lightning stroke carbonized some of it... any of them would make for a
high resistance noisy connection, and possibly a fire in the future. You
might just want to disassemble one of them and see what it looks like inside
and if there is any obvious arcing damage.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net
-----Original Message-----
From: Pete Smith N4ZR [mailto:n4zr@contesting.com]
Sent: Saturday, September 15, 2012 12:03
To: rfi@contesting.com
Subject: Re: [RFI] Noise changes when room lights turn on / off
This may be in the category of "you should never say never, when it comes to
RFI". Back in the 80s, when I lived in a townhouse, I was focusing on 80
meters to finish 5BDXCC. I became aware of local RFI covering two segments
of about 10 KHZ at (wouldn't you know?) 3500-3510 and 3790-3800. It was
there some of the time, and not others, tending to come on in the morning
just before dawn.
I walked the neighborhood with a portable radio, and localized the racket to
a neighbor's townhouse. Though I barely knew him, this very nice guy
invited me in to try to find the source. We looked at instant-on TV sets
and other, similar sources, to no avail. Then, just as I was leaving in
defeat, he switched off a bathroom light fixture (ordinary 110v bulbs, spst
switch). The noise started. Switch on, noise off. Too weird. He
confirmed that he was in the habit of leaving the bathroom light on at night
and turning it off before leaving for work.
Carrying niceness further, he allowed me to replace the light switch, and
though we didn't expect much, that cured the noise! Both the original switch
and the replacement were ordinary 72-cent "silent" types from the local big
box store.
Subsequently, I found another source in yet another neighbor's house, on two
*different* frequencies in 80 meters. They too let me in, and we isolated
it to one of two switches controlling the ceiling light in the kitchen,
again with the noise happening only when the light was off.
Again, I replaced the switch, and again, the noise disappeared.
All these years later, nobody has offered a specific explanation of how this
could have happened. I still have the switches, and have often toyed with
the idea of setting up a test bench to see if they still make noise when
switched off, but never got around to it.
73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com The Reverse
Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000
On 9/14/2012 4:31 PM, Tony wrote:
On 9/13/2012 11:52 PM, Jim Brown wrote:
On 9/13/2012 5:19 PM, Tony wrote:
Assuming it is a house wiring problem and not an appliance, what
would cause it to come on in the evening and stay on till morning?
Would temperature and humidity cause this?
I suspect a combination of things -- a wiring problem that is making
the noise source radiate (or conduct) more effectively. The thing
that makes me suspect house wiring is that you said you switch a
light and the noise changes. THAT'S why I said you should check your
wiring very carefully, and all of us should anyway. The law of
averages says that whoever did your house wiring made at least one
mistake. Some mistakes are a nuisance, some are very dangerous.
Good advice Jim. I checked the switch and the socket today and they
appear to be wired correctly. Wiring is also in good condition. I
shook the outlet and switch to see if noise changed, but nothing
happened.
The only lights that could GENERATE noise are fluorescents or those
that have a DC power supply. It's become quite common for most track
lighting to use a DC power supply, and they are virtually all
switching power supplies. 73, Jim K9YC
Understand. In this case it's a simple incandescent bulb. I'll have
the 12 volt battery in hand this weekend so I can run the rig with the
mains turned off.
Tony -K2MO
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