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Author Topic: Compact fluorescent bulb -- extreme RFI hash  (Read 17962 times)

Posts: 220

« on: April 23, 2014, 09:36:19 AM »

I had a hideous buzz that appeared on the lower end of the MW band about a month ago.  At first, I thought perhaps it was an intermittent power pole noise. Because it mostly centered on frequencies below 650 khz, I just ignored it for a while.

But after about a month of this I decided to investigate.

Taking a portable AM radio around outside, I noticed the noise radiated as far away as about 150 feet, but it seemed to center on my house.  So I took the radio around the house and it seemed to center on the circuit breaker panel.

Switching off the circuits one by one I was able to find the circuit the offender was on, but never could find the source, until by chance I just happened to flip off the porch light, and voila! No more noise.

It was an otherwise perfectly good, normally working compact fluorescent 60W equivalent lightbulb.

Obviously, something inside went a bit critical.  The bulb still works, but I'm not using it.

Posts: 1516

« Reply #1 on: April 24, 2014, 07:53:48 PM »

Could be anything  in your induce noise into the wiring.  Only way to find out is to isolate each room or circuit in the house by pulling the breakers or fuses one at a time.
You could also unplug and turn everything off in each room, especially wallwarts and cellphone chargers. Electric razors especially leading brand name ones  generate nasty buzzes when charging or  while being left plugged in. These big international brand names dont even bother about EMC compliance on their razors. Another band noise generator are those crap touch lamps from china. Cheap as crap and very dangerous wiring practices inside. Be very careful and make sure anything made in china is unplugged before even unscrewing it. They that dangerous!

The best antenna that I have found for finding these problems is a  small HF loop. This can just be a  small coax loop about 1ft in diameter. You can pin point the  noise very accurately with this loop.

If you want to find individual faulty globes or badly designed one, use a test jig. You can get these cheap computer UPS. Make up a wiring loom and plug each globe in and pass the power lead through the loop. This makes a crude EMC test jig. I did this test with all my led globes. The noisy ones I just took  back to the store.  There is a huge gulf in the noise performance of various brands of globes. Even big brand names can be nasty noise generators.

Its unfortunate  but today a ham has to have the tools to find these faulty products in your own house and  from the neighbors. Its worst investing in the equipment to do this.

Posts: 7718

« Reply #2 on: April 25, 2014, 06:10:16 AM »

There's no need to DF devices in your own home. Simply power OFF devices while monitoring the RF noise at the amateur station.

Posts: 1516

« Reply #3 on: April 25, 2014, 09:05:47 PM »

That might be so, however its amazing what you learn  by playing around with a small loop in your house.  Things like wireless modem routers generate wide band hash. In some places they installed in the attic or a utility box for  use with optic fibre. WHen you unsure where the noise is coming  the loop can make pinpointing the source a very easy task. Its my No1 tool for  finding noisy items without  turning off the power.

Outdoors I have used the loop to identify a corroded  and noisy LED garden light. The particular neighbor had 60 of these installed. With the loop I could find the exact faulty lamp.

I use my KX3 with this loop and it makes a excellent EMI finding tool.

There's no need to DF devices in your own home. Simply power OFF devices while monitoring the RF noise at the amateur station.


Posts: 502


« Reply #4 on: April 29, 2014, 12:56:13 PM »

I have learned allot working with a skilled power company tech for the past 6 months with sophisticated RFI sniffing gear.  For power line noise you must locate the noise source that matches the noise signature taken from your shack antenna.  You might get lucky trying to find the noise source with VHF/UHF AM radio but it's unlikely you will find the "correct" source.  I thought I had located several sources all to be proven wrong by the tech.  He was able to find and fix them.  We are still working on finding noise sources after 6 long months.  So far we have found four sources.  Once you find one there will most likely be more. Fun stuff !

CW Academy Advisor (Level II)

Posts: 20

« Reply #5 on: May 05, 2014, 02:19:32 PM »

LED (110v) light bulbs seem to be little noise makers too.

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