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Author Topic: Source of RFI found!  (Read 3595 times)
AJ8MH
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« on: March 06, 2011, 01:54:53 PM »

All along I've been blaming the power company for my intermittent 20 over S9 noise problem all across the HF spectrum, but after two visits, the power company assured me that the noise wasn't being caused by their equipment.

To narrow in on the noise, I used a portable shortwave radio with a built-in attenuator, and noted that the noise was strongest on the power-lines in front of the house down the street from mine.  Walking up to the house made the noise stronger.

Today, I received the telephone number for the renter of that house from their landlord.  The renter was alerted that I would be calling, so he wasn't surprised when I did.  The young kid was pleasant and offered to turn off some heaters, a humidifier and lights while I listened to 40 meters.  Bingo.  It seems the florescent lights in the basement were causing the noise.  He said he would work on the problem, so hopefully this will be the end of my noise.

To be honest, I've never heard this much noise being generated by something other than power-lines.  I was actually very surprised.

This has been going on for about 6 months and caused me to purchase an MFJ-1026.  The 1026 worked, but it's so nice to be able to tune the bands without retuning the 1026 with each band change.

Good luck finding your noise.  73...
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W3HKK
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« Reply #1 on: March 06, 2011, 02:32:48 PM »

I wonder if he might be growing something illegal.....that needs a lot of  light?
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AJ8MH
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« Reply #2 on: March 06, 2011, 03:07:27 PM »

My wife thought of that, too.  As far as I'm concerned, he can grow anything he wants as long as he doesn't generate any hash...on the bands.
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KJ4FUU
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« Reply #3 on: March 07, 2011, 05:33:00 AM »

There was something in either PopComm or Monitoring Times a few months back about a certain brand of "grow light" bulbs recommended for...er...basement gardening that would produce RFI at multiples of something like 2.6Mhz.

-- Tom
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N0SYA
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« Reply #4 on: March 07, 2011, 08:14:06 AM »

lol

basement gardening
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If you have a clumsy child, you make them wear a helmet. If you have death prone children, you keep a few clones of them in your lab.
K2BB
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« Reply #5 on: March 08, 2011, 10:46:32 AM »

Hi guys,
I just found an RFI source right in my basement Smiley
the same story - fluorescent light in a hallway, it adds about +12...15dB of noise on 28MHz...

How do I fix it? Capacitor across the leads or what?
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AJ8MH
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« Reply #6 on: March 08, 2011, 01:33:16 PM »

I talked with the kid again today, because the noise came back.  (He was working on the light.)  He said he's going to give up and buy a new light.  The one he has is old and does not use the newer electronic ballast.  I don't know what he'll end up with.

I have three kitchen counter lights.  Two are to older ballast type (don't cause noise) and one is the newer electronic ballast type.  The new one caused a tremendous amount of RFI on 20 meters, so I pulled it to test on my work bench.

The unit has a pair of blue wires going to one side of the light and a pair of red wires going to the other side.  I twisted the reds together and then twisted the blues together.  Of course, the insulation is kept in place.

Then I twisted the black (hot) and white (neutral) together.  Again over the insulation.  Ya don't want to short anything together.  The green wire was left to connect to ground.

By twisting the wires together, I have greatly reduced the noise to almost zero.  I put the light back under the kitchen cabinet.  Note that the light needs to be grounded to allow the internal noise filter in the electronic ballast to work, so I made sure it was grounded under the cabinet.

I also have a large (two tube) electronic ballast fluorescent light in the center of the kitchen ceiling and it's quiet.

If I were you, I'd try a new light.  You can always bring it back if it causes noise.
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KB4MRX
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« Reply #7 on: March 11, 2011, 05:53:16 PM »

I have a similar issue here, with a neighbor. The problem is caused by unfiltered commercial ballasts in his garage.  Angry Angry
Make sure the new fixtures have a Part 18, Class B, residential ballasts installed.
For example a Phillip Advanced part number RELB-2S40-CS is a two tube T-12 lamp ballast, Part 18 listed for residential use.
By the way, my neighbor has decided to changing them out after receiving a letter for the league.  Grin

Good Luck and 73, Dave
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