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[RFI] Recorded noise vs actual tracking of noise

To: RFI Contesting <RFI@contesting.com>
Subject: [RFI] Recorded noise vs actual tracking of noise
From: Larry Benko <xxw0qe@comcast.net>
Date: Tue, 22 Jan 2013 12:23:24 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
I have tracked noise and other RF sources for a long time and consider myself competent in this regard. I definitely fall in the camp of recording the noise is not that valuable for several reasons:

1.) Recording the noise at different receiver bandwidths, with radio noise reduction on/off, etc. definitely changes the sound.

2.) Just because "your neighbors treadmill" has a certain sound does not mean that all treadmills will sound the same. The RFI from the treadmill is definitely a function of the rate(frequency) that the treadmill motor(s) are modulated. Your neighbor's treadmill might be modulated at 100Hz and my neighbor's one at 300Hz. These"small to the manufacturer" differences change the demodulated sound that you hear as RFI significantly.

3.) Ditto for the streetlights. In one person's area all the streetlights may sound alike when failing but in another part of the country which uses different streetlights there is no guarantee that the sound is the same.

I feel that many folks are looking for a quick fix to identify a noise source. Actually tracking it down is really not difficult. One thing that is very valuable is the frequency spectrum of the noise (periodic or broadband) and any periodicity to the noise such as on only at night, on only in the early morning, 1sec on every 30 sec., 12 hours on/off etc.

I have helped many folks with noise issues but I generally do not get involved with "listen to my recording" stuff as I would only be guessing as to the source. This is my $.02.

73,
Larry, W0QE




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