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
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|