K3RFI - the ARRL power line noise guru - visited my shack three different times
and showed me how he fingerprints power line noise sources.
When you have arcs from metal parts not directly in contact, the arc starts and
quenches several times for each positive and negative peak on the power line.
Counting the number of pulses for each source on a scope hooked to an AM
detector at the frequency of interest will give the fingerprint for that noise
source.
Taking this fingerprint to a suspect pole and tuning a receiver to the 150 mHz
area to a quiet channel will allow pinpointing the exact location of the
hardware arc. The noise can then be investigated using an ultra-sound detector
mounted to the end of a hollow fiberglass pole with the detector on the top end
and a speaker coupled to the hollow pole. The audio down converter will take a
50 kHz noise source down to the audio frequencies.
The 50 kHz detector is sensitive enough for you to rub your fingers together
with the input pointed at your fingers from across a room and hear the
swish-swish of your fingers rubbing.
I have seen this detector used to find numerous bad insulators and when
replaced you would find carbon trails down the sides of the insulators where
arcs had been supported.
In my HF noise case, it was determined that I had in excess of 30 noise sources
and the advice I got from K3RFI and the ARRL was to just move to a different
location. This was after the FCC had notified the power company to eliminate
the noise generated by the power line.
73 - Jim W5ZIT
--- On Wed, 1/7/09, w1ik <w...@arrl.net> wrote:
From: w1ik <w...@arrl.net>
Subject: [Repeater-Builder] Transmitter fingerprinting?
To: Repeater-Builder@yahoogroups.com
Date: Wednesday, January 7, 2009, 3:57 PM
I searched the archives, and did not see this issue addressed.
Please forgive me if this has been covered before.
Is there anyone here utilizing any form of "transmitter fingerprinting"
software and/or hardware to identify sources of interference, either
intentional or otherwise? Can you please provide me with an explanation of just
how you are accomplishing this? Your experience and expertise would be greatly
appreciated!
Thank you!
73
William J. (Jim) Wickstrom, W1IK/NNN0AHC
Technical Director,
Utica/Shelby Emergency Communication Association (USECA)
w1ik<at>arrl<dot>net
www.usecaarc. com
