I have my desktop computer connected to the TV using a 1mtr HDMI cable. I wanted to reposition the desktop and hence bought a cheap 3mtr HDMI cable. With the new cable I noticed that whenever I switch the fan on or increase the fan speed the HDMI connection flickers, similar to unplugging and re-plugging the cable. Apart from that the new HDMI cable works as it is expected to. (It has 4K written on it)

I re-attached the old cable and I could not reproduce the behavior. The new 3m cable is thicker than the old 1m cable hence I assumed it was of a decent quality if not a good one.

I plugged the new HDMI cable to the laptop (connected to the power source) and I was unable to reproduce the problem. My Desktop has GTX 1660TI graphics card with 500W ps.

I would understand about electrical noise if the TV flickers or the desktop restarts/turns off due to power shortage when the fan is switched on. But I cannot seem to understand why is this behavior seen only with this new HDMI cable. The TV doesn't flicker otherwise when connected to the Firestick or never flickered when the 1m HDMI cable was connected.

The TV and the desktop are connected to the same socket (cannot avoid this as there is only one). The fan is in the same hall, perhaps the same circuit, but not connected to the same switchboard. Another fan in a different room does not cause this problem.

Can someone please shed some light on it? How can i prevent this on the cable I bought? What are the implications of this behavior (if any) on the devices connected? In this case the TV and the graphics card.

Well, one might say "Go for a more expensive cable", surely but, I would like to understand the dynamics behind this happening and therefore ensure that the expensive cable wouldn't have the same problem. If this is not the right forum for this topic can someone please point me the right direction?

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    It may be the 3 mtr cable Is a better antenna and picking up the noise causing the problem if this is the only change when moving the computer. The other possibility still along the same idea your cable is in parallel with the power cables in the wall try routing the new cable along a different path.
    – Ed Beal
    Jun 20, 2020 at 14:54
  • "The TV and the desktop are connected to the same switchboard." What do you mean by "switchboard"? The implications, as best I can tell are A) annoyance, and B) frustration. At least you know the cause of the flicker and can avoid touching the fan during a show. At our church, we use HDMI extenders to run the front of house TVs and they will drop off at random times for reasons we haven't yet been able to ID. :(
    – FreeMan
    Jun 20, 2020 at 16:17
  • @FreeMan I mean the same socket. Well its more of curiosity (since its only been few hours i got the new HDMI cable, annoyance & frustration are yet to develop). Jun 20, 2020 at 16:40
  • @EdBeal Yes, that is the only change. The HDMI cable is outside, along with it is an Ethernet cable. In other words it isn't running in parallel with any power cables. Just to provide more clarity, the desktop is right in front of the TV with the 3M cable simply connecting the devices in the open. Can the noise you describe be EM waves since the fan motor and the HDMI cable are in the same room ? I suppose I can try eliminating the cause of a lower voltage by connecting the desktop to a different circuit. If what you point out is indeed the cause. What do you suggest I try ? Jun 20, 2020 at 16:47
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    @ThreePhaseEel I knew you were going to ask that. India. Jun 20, 2020 at 17:48

1 Answer 1


Although some may suggest a better cable it may be the amount of electronic noise from your speed controller, electronic speed controls create electronic noise in the form of harmonics, an external torid on the outside of the longer cable may dampen the noise picked up on the longer cable a ferrite washer shaped disk with the cable running thru it possibly with a extra pass through may do the trick on your existing cable. The next option might be placing a faraday cage over the controller this cage dampens the em noise signal much like a toride or ferrite core. If you have multiple phases or a split phase system moving the TV & computer to a different leg of the system may also resolve the problem. I have experienced many kinds of electrical noise in my career some times even a better (longer and multiple ) grounding rods have helped but more often EMI filters prior to the power supplies have done the most good (emi filters are usually simple capacitive / inductive filters that dump non 50/60hz signals to ground).

  • Accepting this as the answer, as i ultimately ended up moving the system and connected it to a dedicated monitor with a DP cable. Mar 18, 2021 at 6:30

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