[RFI] [BULK] Re: Ambient Noise Levels

Jim P jvpoll at dallas.net
Thu Aug 10 00:37:54 EDT 2006


I think I can sum up what you said then thusly: 

   The multiplicity of non-intentinal emitters in the 
   'skip zone' contributes to the overall observed 
   rise in noise level by the effect of summation of 
   said non-intentional emitters at the receive site. 

(I think, too, that most of us are aware of the mechanism 
by which progation is achived by 'charge movement'
on a wire or other conductor.)

I don't know that I entirely agree with that statement of
the origins of the noise, however.

As many of us are also aware, and can demonstrate
through the use of shielded loops, a LARGE percentage
of received EMI is rather received via "near field" effects
and more specifically the E-field component as opposed 
to "balanced" E-H propagation, travelling wave AKA 
propagated-wave effects, of which class 'ground waves' 
are a member (as ground wave are actually continuous 
diffraction of radio waves over curved earth, with the earth 
acting as the diffracting 'knife edge' beyond which propagation
occurs, and the means by which ground wave propagation 
is effected).

Jim P

----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <rfi at contesting.com>
Sent: Wednesday, August 09, 2006 11:15 PM
Subject: [BULK] Re: [RFI] Ambient Noise Levels

> 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. 
> 73,
> Jim K9YC
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