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??
Mike Weir, VE9KK, is a regular contributor to and writes from New Brunswick, Canada. Contact him at [email protected].

9 Responses to “Monitor RFI issue…..”

  • Kenneth Ascher KK4EIR:

    I had the same problem. I added a second monitor and when I moved the first monitor from behind the radio off to the side it suddenly had an RFI problem similar to your example. I just rearranged the monitors slightly and the problem went away.

    Good Luck,
    73 KK4EIR

  • Mike VE3WDM:

    Good morning Ken, I was thinking along the same path I am able to swap the position of the offending monitor with the P3 monitor. I have some other ideas that involve getting rid of the power adapter that brings the line voltage down to 12v. I am going hook the monitor up to my rigrunner. Also try some snap on chokes on the AC cord as well. Ken thanks for stopping by and taking the time to comment. I will post with the results soon.

  • John K0EBC:

    When I rearranged my office/shop/radio room I decided it was time to track down and cure my severe rfi. each device cable was removed from the HAM PC one by one with the rfi diminishing a little each time. Even with the PC being powered through a filter and the case attached to my common eqpt ground, the rfi remained objectionable. My station is now run via an old laptop and a PC I put together with modern parts.

    While tracking down the noise I ran a little am radio over and around every device and found most USB keyboards and mice and wireless mice emitting lots of garbage. Two older LCD monitors were also noisy. A new monitor is nice and quiet.

    John K0EBC

  • Mike VE3WDM:

    Good morning John, I think this weekend I am going to invest in a cheap AM radio and do the same. Last night I had just a short amount of time so I was able to remove the power adapter from the noisy monitor. I plugged the monitor directly into my Astron power supply but it made no difference. So this weekend I am going to move forward with some other ideas.

  • Cortland ka5s:

    Hi, Mike. I’ve worked in electromagnetic compatibility engineering since 1983, about half of that in the computer industry and have seen all kinds of monitor noise. LCD monitors are often RF sources due to switching power supplies.

    I have a couple of LCD monitors that can run at 12 volts, but I never had enough RF from my displays to try that experiment myself. Try turning off the backlights; monitors with fluorescent backlighting use a stepup SMPS for them.


  • Mike VE3WDM:

    Good afternoon Cortland, first off thanks for taking the time to read the post and also for the info in your comment. I have tried running my 12 volt monitor off the Astron power supply but still have the trouble. I am going to look into the backlighting idea and give that a go.
    Thanks for the great advice.

  • Dave KE*BSU:

    While a spectrum waterfall is scrolling on the monitor, I click on a ScreenOff app which I keep in the Windows 10 taskbar. This instantly blanks the monitor, while keeping everything else running. After a few seconds, wiggle the mouse to unblank the monitor. Then I can see the offending RFI lines in the waterfall. My LED monitor generates lots of them in the 6 meter band.

  • John MW1CFN:

    This problem must be very widespread, but seems little-mentioned in the ham press – for reasons I can’t fathom at all.

    I recently ventured to use a new LG monitor with the aim of making things just a little clearer to see.

    The result? Absolutely horrendous RFI across the entire ham spectrum, with a strength that is beyond belief! Not down to the SMPSU, as it runs happily, with the exact-same RFI, on a 12V battery.

    It seems timing circuitry is to blame, because changing the resolution results in the RFI moving up and down the band – but always remaining strong.

    I’ve reverted to a new laptop with a bigger screen, which is not entirely silent itself, but can be detuned to almost complete silence by adding a cut-and-try wire length croc clipped to the chassis.

    I just can’t understand how all those folks with multiple screens can operate – the circuits (and, hence, the RFI) in these monitors must be pretty much identical across brands. Is it that they are in such RFI-infested places that they don’t notice, or are they putting image before sense?

  • Steve AE2S:

    I just can’t understand how all those folks with multiple screens can operate… I have asked that question over and over. Since I know nothing about monitors I would say it’s inside like the TV tube of old that is causing the issue. It’s not the power adapter. My next guess would be if the monitor is LED and we all know how much RFI a LED bulb emits there is your culprit. How to stop it? Turn the damn monitor off.

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