Topband: A CFL Bulb Issue

Hardy Landskov n7rt at
Tue Mar 25 15:52:02 EDT 2014

They clain they are very long lasting too but I have not found that to be 
the case. Six months to a year is all I get. I don't buy them anymore.
But thanks to Joe for explaining how they work. I did not know.
Hardy N7RT

----- Original Message ----- 
From: "Joe Subich, W4TV" <lists at>
To: <topband at>
Sent: Tuesday, March 25, 2014 11:03 AM
Subject: Re: Topband: A CFL Bulb Issue

> Understand what these compact florescent bulbs really are ... a small,
> tightly coiled, florescent tube with an *electronic ballast*.  The
> electronic ballast is nothing more than a small, cheap switching power
> supply to generate the high voltage necessary to fire the tube.
> When a CFL fails it is invariably the electronic ballast that goes -
> often breaking down (arcing internally) under the high voltage.
> Most of the bulbs these days are quiet in normal operation but once
> they start arcing internally - particularly the bypass and filter caps - 
> it becomes a small spark transmitter with a very large antenna.
> 73,
>    ... Joe, W4TV
> On 3/25/2014 1:37 PM, Steve wrote:
>>> these CFL bulbs can generate some strong RF
>>> noise just before going out.
>> Mack - had a similar issue here several years ago...s9+ buzz throughout
>> the longwave band for a month. I live on an island with very few winter
>> neighbours and eventually traced the source (which was radiating nicely
>> via the powerlines) to an unoccupied summer residence, but still was not
>> 100% certain as the signal was so loud from all of the 11 home's drop
>> lines on the local grid. When the owner returned I had him pull the main
>> breaker and sure enough the buzz stopped. It turned out to be a
>> burned-out CFL bulb in the crawlspace that they left on to discourage
>> any sea otters from trying to get into the space during the winter. The
>> bulb was heavily charred and parts of it had already melted yet it
>> continued to radiate a strong signal. Needless to say they were glad
>> that it hadn't set their place on fire and have since stopped using this
>> type of bulb.
>> Steve / VE7SL
>> Mayne Island, BC
>> WEB - "The VE7SL Radio Notebook":
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