Wednesday, February 27, 2013

Monitor RFI issue.....

RFI from new monitor
This evening I was on the radio and had the Elecraft P3 up and running as always. I just happend to be looking at the P3 external monitor when my PC's monitors went into sleep mode. I noticed that some signals (now seen as RFI) dropped off the screen. I had noticed these signals before and knew it was RFI but had
Both monitors off  
 no idea it was coming from the monitors! My new AOC e2351F LED monitor seems to be the major culprit but the Acer Z233h does add just a little on it's own. If I turn the monitors off (via the monitor button) the RFI is gone or if the monitor goes into sleep mode. You can see from the picture to the right where the RFI was from the tails. So the question now is how does one go about narrowing this down? I have power supplies to each monitor...but would they be the problem if the RFI is gone when the monitors are turned off but supplies are still plugged in? Can you ground a flat screen monitor to my station ground? Could the RFI be traveling down the monitor cables? Well this is just another project to keep me busy. I am lucky that the RFI is not the same on all bands these shots are from 18mhz and it seems to be the worst of them all. Any ideas blog world??

16 comments:

  1. Mike,

    Same problem here with a Hyundai 19" monitor that I recently bought on eBay for the shack. The actual cable to the computer had a ferrite "bead" already installed, so I ran the power cable through one of those snap on ones. Problem pretty much solved.

    Larry W2LJ

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    1. Good morning Larry, I have lots of the chokes around so after dinner to night I am going to get moving on solving the problem. Thanks for the help.
      Mike

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  2. Hello Mike, a lot of stuff is radiating and most of the time we are unaware of it. So I found out that my computer is also a source of qrm. There is a lot of electric, home made noise around here. 73 Paul

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    1. Hello Paul, I have noticed other sources of QRM when the monitor is shut off and not sure where that is coming from. It's not to bad so I may look into it when I get some extra time.
      Mike

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  3. Once, a long time ago. I had the same problems with a monitor. Although it was a old one (not the modern flat monitor) I openen up the case and sticked Alu foil inside. I did use some ferrit clamps as well. It solved half the QRM. 73, Bas

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    1. Good afternoon Bas, with the new flat screens it's almost impossible to figure out how to take them apart let alone fine the room for foil.
      Mike

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  4. Hi Mike

    I have a similar problem with a monitor here but it causes QRM on VHF rather than HF. Looks like I should try some ferrites on the power lead!

    73

    Kevin

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    1. Good evening Kevin, that is going to be one of the many things I am going to give a go this evening.
      Mike

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  5. I was facing the same problem, i use 2x Benq 22" monitors and they cause some interference in the low bands. The quick solution was to move them to a separate power plug and use quality cables, the thicker ones with proper shielding and bigger ferrite chokes at both ends. Also, the videocard (Asus HD6870) in the PC caused some interference (noise in the reciever when i scrolled trough web pages), I replaced with another one (EVGA 8800 Ultra) and everything is fine now.

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    1. Thanks very much for the great ideas I do have some chokes I can use and as for moving the power to another outlet. I will have to check to make sure the plugs in my room are not all fed from the same circuit breaker.
      Thanks again for the advice and taking the time to read and comment on the blog.
      Mike

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  6. Here is an idea from my days dealing with tempest rated computers:

    Spray the external case with conductive paint and attach a ground lead. Once done measure for conductivity from the enda of the lead to various points on the painted case.

    Before you paint, tape aluminum foil to the case and ground it.

    I think tremclad has an aluminum point that is conductive.

    73 de VE3XQQ

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    1. Good afternoon Frank, thanks for taking the time to read the post and give your input. I did try putting aluminum foil around the monitor and ground it but it did not help. I am not sure I am ready yet to get painting the case.
      Mike

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  7. I bought an AOC e2051sn 20" LED monitor today for eventual use in my shack...US$89 special at a local retailer. Haven't actually tried it while operating yet, but I did do a very quick RFI test using a handheld shortwave radio tuned to the 31m band as soon as I got the monitor out of the box. The monitor does produce a squeal loud enough to obscure (but not completely drown out) the Brazilian broadcast station I found when scanning the band. It does not seem to be the supply but rather the display itself as the squeal doesn't start until the LEDs turn on. The monitor looks great, but I am not sure if I'll be keeping it. Thanks for sharing your experiences! 73, Jake, K4ZAU

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    1. Good afternoon Jake, I was able to get around the trouble with just moving the monitor around, choking the AC and monitor line. It's a great monitor and I am using it without any troubles now.
      Mike

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  8. I bought an AOC e2051sn 20" LED monitor today, on special at a local retailer for US$89. Eventually I planned to use it in my shack, but I am not sure if I'll keep it. I did a quick RFI test using a handheld shortwave radio as soon as I got the monitor out of the box. At least on the 31m band, the monitor produces a squeal loud enough to make it difficult to hear a broadcast station which otherwise comes in clearly. And the problem would probably only be made worse if the radio were using AC power. Thanks for sharing your experiences. 73, Jake, K4ZAU

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  9. My experience relates to an LG 21" monitor. Most will be the same issue.

    I could only get around the RFI by: (1) creating a large choke on the VGA cable on a 5" PVC former and (2) paying attention to capacitive coupling, the precise positioning of the DC and VGA cable (preferably, at a 90 degree angle) relative to the monitor.

    I managed to reduce the RFI to almost imperceptible levels on all bands other than 6m, which sounds absolutely horrendous.

    A 10 year-old HP monitor, which has lots of metal casing within the plastic housing, produces almost no RFI by default, even without any of the precautions mentioned.

    At the moment, the new LG monitor is shelved. It's much better simply to spend the money on a decent laptop with a good-sized screen. I've never seen any RFI from my Samsung notepad over 6 years of use (the fact that it's till going afer 6 years is quite something, in itself!)

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