[RFI] Can Fluorescent bulbs cause RFI problems?

dgsvetan@rockwellcollins.com dgsvetan at rockwellcollins.com
Tue Sep 27 12:37:09 EDT 2005


There are two issues associated with fluorescent lights:  conducted and
radiated emissions.

The DIRECT radiated emissions are those from the lamps themselves (the
glass tubes).  Some years ago, when I was in the shielded enclosure
business, we had customers who wanted fluorescent lamps inside their
enclosures because they gave better light than regular incandescent bulbs.
No arguement, but we used regular bulbs in the light fixtures because
incandescent bulbs are a "clean" light source.  Except for a slight glitch
at the moment they are switched on (due to arcing within the switch), no
noise comes from the lamps.  Well, due to customer demand, one of my
colleagues measured the radio spectrum given off by regular 40 watt tubes
(the kind that are 48" long).  He found that the peak spectrum emitted was
around 10 MHz, and that because the field was of a fairly high impedance,
shielding it was rather easy.  The company designed a simple metal screen
that could be fitted over the normal two tube fixture that was effective at
killing the radiated field.  Of course, the fixture had to be metal (most
are) and well grounded (many are not).

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!  (Hint:  magnetic ballasts weigh a lot more than the
electronic ballasts.)  If you go to an industrial electric supply, you
might be able to find some filters specifically made to "clean up" the
power line of fixtures having electronic ballasts.  The shielding company
equipped all enclosures having fluorescent fixtures with the filters (which
installed inside the fixture) and there were no problems, just extra cost.

If you have a house wired with Romex or plastic conduit, that conducted
noise can radiate around via the large area antenna provided by the house
wiring.  Folks with metal conduit get some shielding, but not a lot.

I have 9 fluorescent fixtures in my basement area, all with 2 tubes per
fixture and electronic ballasts, and all running without any interference
to my HF or VHF/UHF operations.  I only have 2 of those compact bulbs
described in the original posting, but I may try using more of them as time
goes by.  I agree that the cost savings, while not great, can add up over
time.  I have no RFI problems with either of those bulbs (both of which are
low power - 40W equivalent types).

73, Dale

             "Michael Tope"                                                
             <W4EF at dellroy.com                                             
             >                                                          To 
             Sent by:                  <rfi at contesting.com>, "Scott Neader 
             rfi-bounces at conte         KA9FOX" <ka9fox at qth.com>            
             sting.com                                                  cc 
             09/27/2005 01:43          Re: [RFI] Can Fluorescent bulbs     
             AM                        cause RFI problems?                 

----- Original Message -----
From: "Scott Neader KA9FOX" <ka9fox at qth.com>

> Hey guys.  I started getting on this kick of replacing our lights in the
> house with Fluorescent equivalents, to obviously save money and do a
> little
> thing to conserve energy.  I've replaced about 25 so far.  They were the
> 60w and 100w basic light bulb equivalents.  I started looking into
> replacements for some of our most used 65w and 75w floods & reflectors in
> the recessed cans around the house when... whoa, what am I
> doing?!?!?!  Could this be a potential RFI problem?
> I searched the archives on this reflector, but not seeing much.  Any
> would be appreciate.  I'll also try some tests with the existing bulbs
> see what I can hear, if anything.
> FYI, what got me going on this was that I seem to be seeing these things
> everywhere I look.  Home Depot sells a 6 pack of the 60w fluorescent
> bulbs for $9.95 a pack, and I just picked up a 6 pack of 100w bulbs for
> $15.50 at Sam's Club today.  The draw to saving 75% of the electricity
> costs and lasting 4-7 years is certainly interesting.  I would think we'd
> be seeing a lot of posts if these things were causing RFI problems... but
> maybe I'm the only ham to be dumb enough to bring them into the house?
> - Scott KA9FOX


I live on a small lot, so all of my antennas are very close to the house. I
have a number of compact fluorescents at very places in the house, I
so far I haven't noticed them causing RFI on the HF bands. I can hear
the ones in the hallway next to my shack on my AM radio in the garage,
but it is very close to the hallway wiring. I don't hear that same noise
when I listen on my 160 meter antenna which is about 20 feet in the
other direction. Same story with the conventional fluorescent tubes
lights in the garage (some noise on my AM receiver that sits right under
them, but nothing to speak of on the outside antenna). As far as dimmers
go, I had one in my old house that was noisy on 80 and 160. I replaced
it with a Lutron which cleaned up the noise. I think the Lutron still
put out some noise in the low medium wave range, however.

I've had a few of the compact fluorescents fail prematurely, but not
a significant number as of yet, so I guess there is still hope for a 6 to
7 year average life and the accompanying cost savings.

73 de Mike, W4EF..................................

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