On 12/3/2025 5:57 AM, Roger Kennedy wrote:
My local noise on all the low bands is just wideband hash from various
neighbours dirty switch-mode PSUs.
Roger,
You seriously misunderstand. SMPS and other electronic noise sources do
NOT create wideband hash. They create harmonics that we hear as
carriers, spaced at intervals of 20-6 kHz, modulated by noise and the
mains power frequency. These SMPS are in all sorts of equipment, from
chargers to wall warts to appliances and home entertainment products.
This noise is also generated by the variable speed controllers for large
and small motors.
Broadband noise is created by arcing, a large fraction of which occurs
at equipment that is part of the mains power distribution system, and by
things like large motors.
The important difference is that electronic noise must be chased on the
frequencies where we hear it, while arcing noise is best chased at VHF
and UHF.
There's a lot about this in both text from a piece I wrote for the
National Contest Journal and slides for talks I've done at Visalia,
Pacificon, and to several ham clubs. k9yc.com/publish.htm Scroll down
to the topic about building contest scores by killing noise.
73, Jim K9YC
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