[Top] [All Lists]

Re: [RFI] [BULK] Re: Ambient Noise Levels

To: rfi@contesting.com
Subject: Re: [RFI] [BULK] Re: Ambient Noise Levels
From: Bill Tippett <btippett@alum.mit.edu>
Date: Thu, 10 Aug 2006 14:41:55 -0400
List-post: <mailto:rfi@contesting.com>
 >Noise here is at least 10dB higher beaming towards
Barnesville or Forsyth during the daytime on my 160
transmitting verticals. Beaming south or north away from
both Barnesville (7 miles to the west) and Forsyth (7 miles
east), noise is 10dB less. That noise shows a steady
increase (except for driving past low level peaks from bad
powerline hardware) as the city is approached.

         I hear the same when switching my Beverages
toward a small (population 400) town ~2 miles away.  I've
always attributed that to the sum of many Part 15 devices
and other unintentional RFI generators (e.g. light dimmers,
switching PS wall warts, fish tank heaters, etc).  I notice
this more on 160 than on 10.

 > considering cumulative effects (that is, many sources
 > adding together to create 'the noise') I cannot at this
 > moment accept

 >Then you are not accepting something that has been very well
known in engineering circles for many years. It is even in
studies by Bell Labs, the FCC land mobile advisory
committee, and the Institute for Telecommunications
Sciences. Reference Data for Radio Engineers and other
textbooks have data that agrees with this.

 >Those bothersome little noise sources don't just go so far
and vanish. They propagate like any other signal. Even if
they are below ambient noise from other directions they
still contribute to overall noise floor. The accumulated
energy of many sources is hurting us already. It has already
been shown that the background noise is up several dB from
many years ago, and it isn't from lighting storms. It's a
blanket of noise from millions of very weak man-made

         Jim K9YC, doesn't the principle of superposition
apply to noise sources?

                                         73,  Bill  W4ZV

RFI mailing list

<Prev in Thread] Current Thread [Next in Thread>