[RFI] Mystery Noise (Aren't they all)

[Jim Brown]

On 1/29/2024 1:53 PM, Michael Martin wrote:
> It's very common to see the noise level drop when turning off the main
> because you have just disconnected a large portion of the antenna which
> will weaken the signal.

Yes! An important, yet very complex problem that depends on a LOT of 
variables. Like what's your OWN grounding and bonding. At the source? Is 
there a transformer between you and the source? Errors in branch circuit 
wiring on either end?

EVERY wire, including parallel or coaxial conductors functioning as a 
transmission line, is an antenna, both for receiving and transmitting. 
All it takes for it to ACT as an antenna is for it to be excited by RF 
and connected to a receiver or transmitter (Noise source). Old farts 
(like me) -- remember feedthrough caps? Ya gotta bypass the RF to the 
chassis!

Failure to bond cable shields to the shielding enclosure at the point of 
entry/exit makes it more likely that noise will enter the victim via 
current on the cable shield, or that the cable shield will act as a long 
wire, end-fed transmitting antenna for noise generated within the box. 
The failure to do that bonding is what the late Neil Muncy, ex-W3WRE, 
exposed in the '90s. A colleague named it "The Pin One Problem," because 
in the world of pro audio, the cable shield is connected to Pin 1 of the 
standard connector used for microphones, the 3-pin XLR. 99.9% of 
consumer equipment is built with Pin One Problems.

73, Jim K9YC