Hey audiophiles...

[danrush]

I know nothing about am/fm reception, etc.  And the kid at the local Radio Shack knows even less.  Here's my problem:  I'm redoing my shop from the studs out.  I have a cheap no-name surround sound receiver that I use for radio.  It works great , super reception...until I turn on the new fluorescent lights.  The lights and stereo are on different circuits. The original antenna leads are attached. 

I can't be the first guy to run into this.  Any thoughts?  I can't stand my own singing!!!

Thanks in advance, Dan

 

[nickao]

Dan verify if it is JUST the radio, which I suspect it is.

Also let me know if it is Just the FM or both AM and FM.

I am guessing just FM, but if both it can be a set  of different problems.

Nickao

 

[danrush]

Nick,  It is just the radio.  Just FM to be specific.  Works great with the lights out. 

(and my work looks better in the dark too) !!!

Dan

 

[nickao]

Well, fluorescent lights act as an RF generator. Even on separate circuits it does not matter. These high frequency(Fm) signals are on the entire electrical system of your home. So it is possible to fix the problem by using an RF filter right at the outlet where you plug in the surround sound. Changing the location of the unit itself and the wiring and/or changing outlets all can help or hurt, with or without the filter. In general using a power-line RF filter to repair it, works.

Here are some highlights from articles I have on hand.

There are two basic strategies to control RFI. The first prevents it from coupling in the first place by using filters or arc snubbers at the source, relocating equipment or rerouting cables, using signal path ground isolators or adding shielding or ferrite chokes to cables.

The second filters out the RF, when possible, after it is coupled but before it reaches a sensitive active device in the equipment. The following recommendations can help prevent or cure most RFI problems.

Locate and treat the offending source.  Your lights are the source

Keep cables as short as possible, and pay attention to routing. A long cable not only increases power line common-impedance coupling (for unbalanced cables), but it also makes the cable a better antenna. Routing cables close to such ground planes as metal racks or concrete floors will reduce antenna effects. Never coil excess cable length.

Use cables with heavy gauge shields. and Maintain good connections.

Do not add unnecessary grounds.

Use ground isolators in problem signal paths. Beware that poor-quality units can often degrade signal quality.

Install RFI filters in the signal path.

Hope it helps

Nickao

 

[robtonya]

Nick,  It is just the radio.  Just FM to be specific.  Works great with the lights out. 

(and my work looks better in the dark too) !!!

Dan

NOW THAT IS FUNNY RIGHT THERE

 

[TemplatesByNumbers]

Dan,

Are you using an external aerial for the FM? A roof mounted aerial, or failing that positioned in the roof space, will give you much better performance (less hiss and interference) even in a good reception area.
Connect it using coax cable, routed to avoid parallel runs with power cables (crossing power cables at 90 degrees is acceptable).

Andrew

 

[Dave Ronyak]

Well, fluorescent lights act as an RF generator. Even on separate circuits it does not matter. These high frequency(Fm) signals are on the entire electrical system of your home. So it is possible to fix the problem by using an RF filter right at the outlet where you plug in the surround sound. Changing the location of the unit itself and the wiring and/or changing outlets all can help or hurt, with or without the filter. In general using a power-line RF filter to repair it, works.

Nickao

Nick,

You are absolutely right in stating that fluorescent lights can generate RF energy.  If you open up one of those light fixtures you should find a tag or label indicating compliance with standards.  But my experience has been that not all lights that are marked as compliant (RF emissions below a certain level) are actually compliant.  My house and older garage section has T12 lamps with traditional electromagnetic ballasts (transformers and circuitry).  Operation of any of these >30 year old lamps cause zero interference with any radio or TV in my house, including any with a "rabbit ears" antenna.  The new section of my garage is equipped with T8 lamps with solid state ballasts; these made-in-China "Commercial Electric" brand units purchased from Home Depot are marked as if they are FCC compliant, meaning they are not supposed to create RF interference with other communications devices.  Well, frankly stated, they are crap in this regard.  Whenever they are energized, they cause noticeable interference with an antenna equipped analogue TV that is in the kitchen which is adjacent the old garage and ~30 away from the closest T8 unit in the new garage.  And these Chinese lamps also hum/buzz far more than any of the much older T12 units.  So much for new solid state technology. 

All of the foregoing is prelude to saying that fluorescent lamps can be generating RF interference both in the electrical wiring and in the air.  I use a battery powered radio when working in the new garage section which is also my shop.  All of the wiring involved is not more than 6 years old, professionally installed and compliant with code.  You might also try isolating your fluorescent lamps to determine if one or more units are generating the undesired RF noise, and use a battery powered radio or TV to determine if that RF noise energy is traveling through the wiring, the air or both.  Filters may be needed not only on the electrical supply but also on the antenna circuits since airborne RF won't be eliminated by filters in the wiring.

Dave R.

 

[nickao]

Yes, Dave of course the magnetic ballast do not cause the interference it is the newer electronic ones that do.

The garbage that gets conducted onto the power line from fluorescent lights comes form two sources: The plama within the lamp (not a real strong source) and the electronic ballast that operates the lamp(s).  If you can manage to find any fixtures that have the old magnetic type ballasts in them, USE THEM!

But as you said it may be the interference in the air. In a tight garage like that with a lot of  lights you are bound to have problems.

Dave what filter do you suggest, a high bandpass filter at the antenna inputs? There are so many filters and ways to install them it is easy to get confused.

Nickao

 

[Qwas]

I hate using filters on the antenna line because they rarely help the problem. And most of those filters are so poorly designed that it is a rip-off to the consumers.

I think the problem is the no name surround sound radio. Cheap radios are cheap because they lack any and all filtering. Try putting the radio in different locations as far from the lights as possible first. Try to enclose the radio in metal, even if it is aluminum foil. Try grounding the metal enclosure. Are you trying to listen to a distant station? Try a local, strong station. A stronger FM signal might over ride the interference. If the speaker wires are long, try winding the excess wire on a 1/2 or 3/4 inch diameter wooden dowel. Do the same with the power cord to the radio and/or the lights.

Are the lights still in their metal case? That case helps to stop interference. The transformer should be completely enclosed by a metal case. Hopefully the power cord to the light should be 3 prong and the green ground wire from the power cord should be attached to the metal case. Make sure the plug the light cord plugs into has a ground wire hooked up. Try moving the light in different directions and see if the interference changes.

If any of this makes a difference, let us know and we can provide more help.