I've got a situation where I have an X-10 Lamp module plugged in near my stereo. If the X-10 is in the ON or Dimmed state I cannot tune any AM radio stations - all I get is noise. Turn X-10 module off and it works fine. Other than removing the lamp to another area of the room or moving the X-10 module to a different circuit, neither of which are practical due to the physical setup of the room, is their any cure for this?
Are X-10 modules inherently noisy and known to interfere with broadcast radio reception?

I've tried different lamp modules with the same result. The module I'm using is the standard X-10 LM465.

That sort of interference is not unique to X-10 light dimmer modules. Dimmer modules in general, create some RFI (radio frequency interference). Some are better than others. My experience is that the X-10 dimmer modules are about average in terms of RFI production, compared to other non-X10 dimmers.

If you don't need the dimming function (just on/off), try an appliance module. Those use a relay to turn the power on and off, to whatever you have plugged into them. Since the appliance modules lack the RFI producing dimmer circuitry, there shouldn't be any problem listening to the radio.

John Galvin

Thanks for the quick reply John. I really do need the dimming capability as the whole point of my X-10 project (which has now taken on a life of it's own) was to be able to bring down the lights in my home theater remotely with my MX-500.

Use of AM radio by me is almost non-existent so I can certainly live with the problem, but in my usual strive for perfection I'd like to see if this can be solved in some way. Are there any noise filters designed specifically for this problem or does anyone know of a plug-in dimming module that is not as problematic in this way?

Firstly, you have to determine whether the interference is radiated through the air, into the AM radio's antenna, or is being conducted through the power lines. If it's a battery operated radio, we can rule out the latter case. For an AC powered AM radio, there are plug-in RFI filters available at Radio Shack and other electronics stores, that may improve the situation for conducted noise. You'll want to use the filter on the radio, not the X-10 dimmer module. If the problem really is radiated noise, other than trying all the different brands of X-10 compatible dimmers, the only thing that you can do, is to provide a better antenna for the radio. It's a pretty long shot, but if there is a connection for an external antenna, then that is the way to go, but most radios these days, use a ferrite rod antenna for AM reception. If that happens to be mounted external to the radio, you may be able to re-orient it, to maximize pickup of the stations you're listening to and minimize pickup of RFI from the dimmer.

John Galvin

Thanks John. I'd like to check out RFI filter from Radio Shack but I can't seem to locate any plug in RFI filters in the most recent catalog or on-line. Any chance you have a part #? BTW, I'm using an indoor Terk antenna on the receiver.

Try this one:
[Link: radioshack.com]

Radio Shack Catalog# 15-1111.

Is this Terk antenna meant to work for the AM band in addition to FM?

John Galvin

thanks for the part #. Yes, the Terk has two sets of connectors, one for AM, another for FM.

John - just thought I'd follow up. I got the AC Line filter and unfortunately it had no effect, so it seems that the RFI is thru the air and not the AC line. Seems like my next step will be to experiment with the antenna some and perhaps try different dimming modules and see if anything is quieter.