September 2012
I have installed some 8' HO fluorescent lights, and now the FM radio has too much noise.
I put four snap-on RF chokes on the power cord at the radio. They did reduce some of the interference and I even plugged the line into a surge protector.
Is there anything I can do at the fixtures to knock out this RF problem?
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First, get a battery operated FM radio and test with that. If the noise is still present, it is coming over the air and the only way to stop it is to turn the lights off or replace them with something else that doesn't generate RF hash.
If the portable radio shows no sign of the noise then it can be licked by more filtering of the AC either coming out of the lights (the best place to put the filters) or at the radio.
I would start, as you did, with the radio side and try more and different kinds of RF noise filters. Once an acceptable solution is found, I'd do my best to find a way to add these solutions to each light socket to kill the stuff as close to the source as possible.
Digi-Key has all sorts of RF line-filters www.digikey.com/product-search/en/filters/line-filters/3408328?k=rf%20filters
Schurter Inc calls theirs EMI/RFI Line Filters www.schurterinc.com/content/view/full/25502/(language)/eng-GB
For more, do a search on-line for "rf ac line filters" or "RFI AC Line Filters"
MFJ might be another good source since Hams don't like EMI or RFI getting into their radios: MFJ-1164B AC Line Filter www.universal-radio.com/catalog/protect/4743.html
MFJ usually has a 100% satisfaction return/replacement guarantee for 1 year but I didn't see that mentioned for this product.
Your noise is probably radiated more than line coupled. Try putting the ferrite chokes on the power lines to the light.
Trapping at the receiver will not suppress the radiated interference! Surge arrestors are not designed to trap noise like this unless they include a noise filter, and then only trap line carried noise.
The first question that comes to mind is if Mr. Robin is 100% certain that the interference is on the power line side of things.
Generation of RF energy at 90 MHz these days is as easy as pie, and it's quite possible that part of (or most of) the problem is RF interference as opposed to noise on the power line.
Years ago, when I worked at installing 2-way radios in Police cars, there were numerous problems with a braking module on one particular type of automobile, causing enough radiated RF at about 155 MHz, so as to make the radio virtually unusable at low signal levels on a channel in that range. The modules had to be replaced.
My suggestion would be to use an FM radio powered from batteries to determine the source. If it is RF then the radio being powered by batteries will be just as affected as the one powered by the AC line.
The best answer in that case may be to try to increase the desired RF signal for the radio with an outside antenna. Replacing the lights or filtering the (probably) electronic ballasts may be quite expensive.
