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

[Patrick Dyer]

For a long time I had a similar puzzling noise on 20m that shifted in 
frequency when the central air conditioning unit came on/off.  As I'm on 
that band only for contests with a low fan-dipole antenna it wasn't a 
high-priority item to track down.

Then one day with a 30-50 MHz receiver on I happened to walk thru the 
dinette and heard it.  It was quickly isolated to the charging unit for 
a pair of (c. 2002) Cobra FRS handhelds there.

Sometime before this that circuit had triggered a warning on an APC UPS 
unit when plugged in there.  A Klein RT100 tester says "open ground". 
 From the get-go here in Jun 1972 it had been noticed that some 
non-polarized plug metal appliances would present a tingling to the 
touch if plugged in one way.  If this had been determined to be a 
contractor-wiring error at the start a demand for remedy would have been 
instituted.

73, Pat - WA5IYX