The most effective device I
have for tracking MF noise is a vintage transistor AM
radio. These old radios are available for a dollar or two
at garage sales, and for a few tens of dollars on eBay.
Here's a link to photos of my favorite noise-hunting radio:
a Motorola transistor radio from 1971.
It is completely portable
and has an internal bidirectional loop antenna. You can
couple the radio close to possible noise sources to hear the
sound of the interference and pinpoint the source. And the
nulls off the ends of the radio are quite sharp so you can
take bearings and triangulate more distant sources.
I tune the radio to an
unused broadcast channel and listen to the background
noise. I go toward the bottom of the AM band (550 kHz) when
I am interested in the noise bothering 630m and the other
services below the AM band, and tune toward the high end of
the AM band when I am interested in 160m or HF noise
sources. Usually very helpful, and often the noise I am
seeking is spewing all across the band so tuning is not
critical (other than to be tuned between active broadcast
stations on an open frequency).
The horizontally-oriented
design radios like this one often have a longer ferrite loop
antenna inside which makes for higher performance, deeper
nulls, etc.
I describe using this radio
to track noise in my presentation:
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Radio is
your best
entertainment value.
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Mein
Ohr ganz nah am Weltempfänger...