[RFI] Ambient Noise Levels

Jim Brown jim at audiosystemsgroup.com
Thu Aug 10 00:15:53 EDT 2006

On Wed, 9 Aug 2006 21:58:25 -0500, Jim P wrote:

>Are you saying that you hear power-line (and other 
>non-intentionally generated, incidental) 'noise' (like
>blenders, brush-type drill motors and the like) originating 
>from far away, e.g. hundreds of miles, and the signals 
>will 'propagate' having been created in large numbers 
>from populated areas into signal strengths at distance 
>that are then heard as wideband continuous noise 
>sources when band conditions are favorable? 

Yes, and this is exactly what W8JI is saying too. When noise is 
generated, it can cause current to flow in a wire, and that wire 
will act as an antenna, just like any other wire carrying RF 
current. And just like any other antenna, its relative 
effectiveness as a radiator and its directivity will be determined 
by its dimensions, geometry, and orientation. You may hear the 
ground wave signal if you are close enough to it, and if band 
conditions permit, you can hear the skywave signal just like any 
other signal generated at the same place and time. And you won't 
hear only one noise source, you'll hear many. 

Radio is radio. Mother (or father) nature doesn't care whether the 
EM wave is generated intentionally (i.e., by a ham transmitter) or 
accidentally (by some noise source). The waves differ only in 
their content -- i.e., signal or noise and their strength. 


Jim K9YC

More information about the RFI mailing list