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Re: [RFI] IR Illuminator for Security Cameras

To: rfi@contesting.com
Subject: Re: [RFI] IR Illuminator for Security Cameras
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 30 Jan 2022 11:42:15 -0800
List-post: <mailto:rfi@contesting.com>
On 1/30/2022 10:55 AM, Michael Tope wrote:
I am not aware of any interference from the IR LED arrays that are built into the cameras, but just in case these illuminators are more problematic I thought I would run this by the reflector before I press the "add to cart" button.

Hi Mike,

Thanks for the QSO last night. Great to hear you on the air again.

99.9% of what gets plugged into the wall includes a switch-mode power supply, 99.99% of them are noise generators, and any attached wiring (like AC and DC cables) is an antenna that radiates the strong common mode component of the noise. Over the years, I've collected boxes of linear DC supplies, from which I find one to replace them. When they're built into a product (TV, stereo gear, refrigerator, etc.) serious common mode chokes on all attached wiring is the only solution, starting with those cables likely to be the strongest radiators.

DC-DC converters used inside products like computer speakers that power from USB are also noise generators. Neighbor W6GJB had so much on the pair in his shack that he could measure the common mode current with an MFJ device!

73, Jim K9YC
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