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

[Eddy Swynar]

On 2012-09-15, at 8:03 AM, Pete Smith N4ZR wrote:

> 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.
> 


Back about 23 years ago, when we still lived in the 'burbs, a neighbour three houses away from me complained that I got into her telephone. This only occurred on those times when I operated 10-meters, which was a LOT at the time, too, on account of favourable conditions back then...

Well, I wrote to the phone company, & they replaced her units with upgraded "...new and improved" ones---yet the RFI persisted, sporadically. So I enlisted help from a coupla Hams at the local club: they descended upon my place, & the testing began in earnest. My buddies could hear no RFI whilst I stayed in my shack & put a signal on the 28-MHz band---yet she insisted she could still copy my signal through her handset!  So I walked over to the house, and myself took the handset & listened, while the guys at my place went on the air. I was SEATED at my neighbour's couch, the phone beside me---and I heard nothing. I passed the handset to my neighbour who was STANDING nearby---and she claimed it was still there! I could not believe her, and in frustration I arose off the couch, put the handset to my ear---and lo & behold, I could hear the interference as well!

Incredibly, the coiled handset cord while I was seated was immune to RFI---but as soon as it was outstretched, it must have acted like a resonant loaded vertical on 10-meters! 

No amount of handset bypassing / filtering ever eliminated the RFI in the cord's uncoiled state...but happily we moved out to the country shortly thereafter, & that sad episode in my Ham career was at long last behind me...

~73~ de Eddy VE3CUI - VE3XZ