Topband: NR-1 noise reduction unit.

[Jim Brown]

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