[RFI] Chasing RX Noise

Jim Brown jim at audiosystemsgroup.com
Sat Nov 2 16:42:13 EDT 2019

On 11/2/2019 5:39 AM, David Robbins wrote:
> wideband unstable noise is likely power line related, but could be dc
> motors, fishtank heaters, or other unregulated devices.

This is FAR too generalized. My application note and slide deck on 
chasing noise includes waterfalls showing how to distinguish power line 
noise from other sources. They look VERY different. In short, noise 
generated by the power system is ALWAYS IMPULSE noise, caused by arcing, 
so it will appear as horizontal lines on a fast waterfall. Noise 
generated by the devices listed above generally appears as VERTICAL 
traces on a fast or slow display, usually with some degree of frequency 

Those differences are VERY important -- impulse noise is extremely 
broadband, falling in strength at higher frequency as you get farther 
from the source, and when you get close, is best chased at VHF/UHF. 
Electronic noise is NOT broadband, and must be chased on the frequencies 
where you hear it. In both cases, classic DFing techniques apply.

73, Jim K9YC

More information about the RFI mailing list