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Author Topic: Plasma TV EMI  (Read 3258 times)
KB3ONA
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Posts: 84




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« on: March 06, 2008, 07:33:21 PM »

I recently encountered really bad QRM on 30 meters and below and couldn't figure out the source. It was on all bands 30 meters and below but seemed to increase with the lower frequencies. The noise on 40 meters was so bad I could only hear the strongest stations. Typically it would be S8 to S9 on 40 meters and 20 over for 80 and 160. My antenna is a full wave 40 meter loop, which I've read is supposed to be quieter than most but mine was definitely not. I happened upon the source by accident the other evening when I was trying to listen in on 40 meters and noticed the QRM abruptly disappeared. Upon investigating I discovered the XYL had retired for the night and the new Panasonic plasma television had been turned off - that was the only thing that changed from a few minutes prior. I left the radio on and turned on the television while listening for any QRM. Immediately the QRM was back at S-9. I noticed as the image on the screen changed so did the noise. I moved the television to different spots in the house but no matter where I located it, the noise was always S-7 to S-9. As a result I went back to Circuit City where I purchased the TV and explained the problem. The manager was very nice about the whole ordeal and agreed to exchange the plasma for an LCD. I've never heard of any EMI problems with LCD's so hopefully I can put this problem behind me. I felt compelled to post this information on plasma TV's because I'd hate to see anyone else run into the same problem. There are still a lot of plasma's on the displays at the various stores so think carefully before you buy. I'll enter another topic on the new LCD after some time to let everyone know if I have any problems.
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N3OX
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« Reply #1 on: March 06, 2008, 08:47:30 PM »

"I felt compelled to post this information on plasma TV's because I'd hate to see anyone else run into the same problem"

Just be thankful it was yours and not your neighbor's.



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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WA1RNE
Member

Posts: 825




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« Reply #2 on: March 14, 2008, 04:37:10 PM »

 Plasma TV's - depending on the brand and model - can cause considerable QRM across 160-20 meters.

 As I and others have posted before, adding ferrites to the line cord or other interface cables - even HDMI, component video, etc. - does nothing to help.

 The source of the interference is the screen itself which has to do with the HV supply and current waveform that results from igniting the plasma within each pixel - and there is no way to stop it, other than putting the TV inside an RF-tight shielded room or redesigning the TV.

 LCD's do not use HV power source to ignite a plasma but instead use HV to fire a backlight which luckily for most amateurs does not result in a harmonic-rich current waveform that runs across all our HF bands.


 ...WA1RNE
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VE3TMT
Member

Posts: 396




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« Reply #3 on: March 17, 2008, 11:11:37 AM »

I had heard about RFI from plasma televisions. So I went the route of LCD. I ended up with a Samsung 40" 1080p LCD model number LN-T4061F. The TV sits about 20 feet from the hamshack and I experience no RFI of any kind on any band from this TV. And it has an amazing picture to boot!
On the other hand, my RCA 32" tube TV is an RFI pig. Can't wait for it to die!

Max
VE3TMT
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W6GF
Member

Posts: 161




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« Reply #4 on: March 18, 2008, 04:31:09 PM »

Are you kidding....I am trying to figure out how to hook an antenna to the screen and key it.  I think it would out do my AL-1500.  The big screen Plasma Panasonic TV is a prolific RF generator.

George, W6GF
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WD2AHP
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Posts: 5


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« Reply #5 on: August 16, 2008, 08:14:48 PM »

I have heard this is a common problem with plasma tv but not with a sony plasma tv.


http://www.westfloridacomponents.com

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VK4KX
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Posts: 12




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« Reply #6 on: March 24, 2010, 01:40:11 AM »

So has anyone got a practical fix for the RFI from the Plasma TV's. My Plasma and others in the local area seem to flatten my needle on the low bands.
If that wasn't bad enough we had Solar Panels fitted; the grid connect type and man do they cause QRN 20db/9 every 25 kc on all bands and 60db over on 29FM.
I asked the installer before we went ahead with it if the inverter would cause any RFI to my Ham station and he said no. I guess he had no idea what RFI was. At least I can turn it all off if I want to use the radios, but I can't sneak over to my neighbor and turn theirs off, oh the pain of modern life.
I want to go back to the days when we complained about S3 QRN.
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WB4BYQ
Member

Posts: 179




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« Reply #7 on: March 24, 2010, 07:48:41 AM »

There is a youtube video with a ham using a Timewave anc-4 noise canceler and it seems to work.  search with
google on timewave anc-4 and MFJ-1025 and MFJ-1026 and look at the information.  common mode chokes on the ac part of the inverter or brute force ac filters may fix the problem.  there are many knowledgeable hams on eham
and previous posting that could help on the rfi.
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KC6WGN
Member

Posts: 110




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« Reply #8 on: April 04, 2010, 10:56:01 AM »

I have 50 inches Panasonic Plasma TV which so much RFI to my ham radio on 20m,40m & 80 meter bands in the house and even in the mobile radio about 30 feet away still that hushing noise is there.When I turn off the tv hushing noise was gone...
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