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Author Topic: Home Brew Noise And Signal Filters  (Read 4131 times)


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Home Brew Noise And Signal Filters
« on: December 20, 2006, 10:46:01 PM »

Over the years I have read many articles in this formum and elswhere about making your own X10 noise filters (also used to prevent signal sucking).  Several years ago when the first switching power supply came into the house I faced the decision to build or buy my first filter.  I took the cheapest possible way out.  I wrapped about 20 turns of #16 insulated wire arouind a 3/8 inch steel bolt, put it into a 2x4 electrical box with a short extension cord and a duplex outlet and plugged it in.  It worked - sort of.

About two years ago I found very inexpensive 22 uh 4 amp chokes on the Internet and have been using them ever since including replacing the 3/8 inch bolt. There was a link to them here but they are no longer available.

Here's the wiring diagram for up to four amps:

Here's the wiring diagram for eight amps:

You'll notice that I used a choke in both sides of the AC line not just one side and that there is no capacitor!  I arrived at this configuration by trial and error and it works so well that our upstairs TIVO box (both of ours are major noise generators) is on the same outlet as the CM-15A with no interference whatsover.  The 8 amp configuration completely filters the noise from our heavy duty Pansonic microwave.  Others filter the noise from switching wall wart power supplies.

Here's the portable filter for our laptop.  It's made from the case of a burned out X10 module.

If you don't have an old module case in your junk box here's what the 2x4 electrical box filter looks like. This is a 4 amp unit.  The 8 amp unit for the microwave looks the same. It's nice to save old AC cords for applications like this.  By the way the surge protector was added quite a while after I verified how well the basic chokes worked although I'm sure it helps.  The unit shown provides provides power to both a TIVO and an LCD TV.

Finally, heres a modification of one of the outlet strips under my desk to filter all the wall warts plugged into it.


I don't recomend using plastic electronic boxes for these chokes because they might not be able to withstand the heat of a short circuit or an overload.  The X10 cases and metal boxes should be able to.

Don't tackle making these yourself unless you're familiar with line voltage wiring or know someone that can help you with the project.

KEYWORD LIST: (So this post will come up on filter searches.) AF100, AF120, AF300, AF310, AC100, 6287, 6288, 6289, XPF, XPPF. This list is taken from TakeTheActive's comprehensive filter link post at:

« Last Edit: October 24, 2009, 09:23:48 PM by Oldtimer »
Having "fun" with X-10 since 1980.

Brian H

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Re: Home Brew Noise And Signal Filters
« Reply #1 on: December 21, 2006, 07:07:11 AM »

Thanks for the information. The chokes in the neutral are a plus as most X10 filters I have seen only filter the hot wire. Though they use a few caps in them also.
Metal box also shields the wires better than plastic for noise


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Re: Home Brew Noise And Signal Filters
« Reply #2 on: December 21, 2006, 08:20:30 AM »

Thanks Oldtimer.
This looks like an practical and inexpensive way to add noise filtering. :)
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