[RFI] Power line Noise

Jim Brown jim at audiosystemsgroup.com
Thu Jun 8 19:28:44 EDT 2006

On Thu, 8 Jun 2006 18:46:34 -0400, RFI Services wrote:

>I think I forgot that important point concerning signal level changes. Power
>Line noise is no different from other RF signals in that its propagation can
>be effected by weather.

Yes, but I suspect that propagation is USUALLY less of an issue because the 
sources are usually too close to the victim to be affected by weather-related 
changes in propagation. That is, weather-related effects don't begin to show up 
at short distances (tens of miles). Most RFI is within hundreds of feet. So 
when there is a variation in strength of the RFI with weather, it is usually 
the effect of the weather (mostly humidity) on the generation of the arc. 

The word "usually" is important here -- we all know that sources of RFI can be 
relatively strong, and connected to relatively efficient antennas -- I'm 
thinking power supplies with strong RFI content connected to long runs of 
unshielded wiring. Hams in remote, relatively quiet locations, have reported 
hearing RFI from sources miles away. And we all know that T-storm static in the 
MF and HF spectrum will propagate for hundreds of miles, just like any other 
signal in that spectrum. 

Jim Brown K9YC

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