sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring AM Radio Interference

One of our customers, a large retirement home, has a unique problem. The last two rooms at one end of one wing have issues with AM radio interference over their telephones. The problem is intermittent and the on-site person there seems to think it is dependant on the weather, as in when its hot and muggy, thats when they get the interference. Of course the day I went to check it out the lines were clear(75 degrees and a nice cool breeze that day). Anyway, my question is, is there logic behind the coincidental weather/interference thing, and is there any sort of filter I could buy/build that may help with this. She has tried a DSL filter which has helped her in the past with other phones experiencing radio interference but it does not help here.

I believe Radio Shack carries RF filters. You could try grounding the unused pairs on one end.

It's probably an un-balanced pair from the telco....their problem. Unless they hear it, good luck getting them to change it.

You could try a couple of .001 mfd capacitors from tip and ring to ground, or check out the RF chokes from Mike Sandman.

Weather forcast seems to say that this week you should have no problem with the "warm and muggy"
The sandman filters are frequency dependant so you will need to determine what station is playing and then go from there.

Does there happen to be an AM radio station nearby? I've run into this before - at the top of our mountain is a FM transmitter and the curly handset cord picks up the station. No line filter helps. It was also intermittent but I haven't heard it since the most recent round of analog phones I've been using were installed.

my mother lives about 4 km from a 50 000 watt clear channel blowtorch. she could hear them clear as day until i grounded the un used pairs and stuck a DSL filter on each phone, problem disapeared.

Travis,
We have used these with great success.

Thanks for all the responses. These room phones are analog ext's off of a Toshiba CIX. There is an FM radio station and tower a block away and they do periodically have issues with FM interference but the gal there just throws a DSL filter on the phone end and that will always take care of the FM problem. The AM problem is limited to just a few rooms at the end of one wing. As far as I can tell the only thing they have in common with each other is proximity. They all go back to the same IDF but on seperate cables along with probably 50 other room phones that do not experience the issue. When they do get the interference, it is really quite loud, at times almost too loud to carry on a conversation.

Oh and the real kicker is, its a religious radio station. It just so happens the the residents in those rooms don't share the same views as that of station.

I will give these Sandman filters a try. Thanks again.

We have a area in town that gets a Spanish am radio station and it won't go away, it's always been there we use the same thing Mike suggested , they work great.

For AM reception the circuit is likely a multiple of the frequency the station uses making it a really good antenna. The filter should help. If not you can try de-tuning the antenna effect by adding some cable to the circuit.