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[RFI] Chasing RX Noise

To: rfi@contesting.com
Subject: [RFI] Chasing RX Noise
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sat, 2 Nov 2019 13:42:13 -0700
List-post: <mailto:rfi@contesting.com>
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 instability.

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
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