[RFI] Noise changes when room lights turn on / off

[Pete Smith N4ZR]

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 at arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>
>
> -----Original Message-----
> From: Pete Smith N4ZR [mailto:n4zr at contesting.com]
> Sent: Saturday, September 15, 2012 12:03
> To: rfi at 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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