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Re: [RFI] Smoothfitness 6.25 Treadmill RFI

To: rfi@contesting.com
Subject: Re: [RFI] Smoothfitness 6.25 Treadmill RFI
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 13 Sep 2016 09:52:50 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Tue,9/13/2016 8:44 AM, Lionel Booth wrote:
My question to the group is whether there is any specific experience with this 
manufacturer as guidance when I rip into this monster?


Lionel,

The noise is produced by a switch-mode power supply inside the unit, and is probably radiated as a common mode signal by the AC wiring. That part of it can be killed by winding the power cord through one or more #31 Fair-Rite cores to form a common mode choke. Follow the guidelines in Chapter 7 of k9yc.com/RFI-Ham.pdf for the bands where you hear the noise, and for coax the size of the power cable. That is, if the power cable is the diameter of RG59/RG8X, use the guidelines for that coax.

There may be more noise radiated from internal wiring. For that, you'll need to go inside the box.

AC line filters are a waste of money for this sort of problem.

73, Jim K9YC

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