[Help] HDMI Completely Knocks Out 5GHz Wi-Fi

Discussion in 'Computer Hardware, Devices and Accessories' started by NekoMichi, Sep 7, 2017.

  1. NekoMichi
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    NekoMichi Retro Collector

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    So this really bizarre problem just started happening today and I was wondering if people could possibly help diagnose or solve it.

    I am currently using a TP Link D2 AC750 router in 2.4GHz and 5GHz simultaneous mode, and this is situated near several media devices that are connected to a monitor via an HDMI switch box. Normally all of these work perfectly together however starting from today a strange problem arose that won't go away. If any of the media devices are active and sending a video signal to my monitor, the 5GHz network gets knocked out immediately. While it still shows as being active in the router's config page, none of my devices are able to detect it at all. As soon as I turn off whatever's connected to the monitor, the 5GHz network instantly re-appears and is functional again. The 2.4GHz network is unaffected entirely.

    The three media devices are a Nintendo Switch, an Apple TV (4th generation), and PS4. I have tried removing the HDMi switch box and connecting these devices individually to the monitor, and all three can still knock out the 5GHz network even when the other two are completely disconnected and the HDMI switch removed. Rebooting the router does not fix the issue. If I connect my laptop (situated 1m away from the router) via HDMI, it does not affect wireless signals.

    I have not changed the software nor the hardware configurations of this setup, and this problem seems to have just started spontaneously. How is this even possible?
     
  2. DarkFlare69

    DarkFlare69 GBAtemp Psycho!

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    I never knew it was even possible for wired signals like HDMI to interfere with wireless signals.. Is it possible you could move the router away, like a few meters, or move all of the other devices away?
     
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  3. Tom Bombadildo

    Tom Bombadildo SkyTom

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    I forgot
    You say it's whenever the device is outputting video, but what happens when the device is on, without outputting video? It works just fine?

    Are all these devices being powered from the same outlet/power strip?

    It sounds like one of two things, either something is causing interference with the 5ghz band (you probably shouldn't have all those devices that close to your router, btw), or power consumption issues if they're all on the same outlet.

    EDIT: Try changing the channel your WiFi uses for 5ghz, see if that changes anything.
     
    Last edited by Tom Bombadildo, Sep 7, 2017
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  4. chrisrlink

    chrisrlink Intel Pentium III Hamster inside

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    inside your crappy old PC
    have you tested 2.4 mode with the same pc? (or like a 3ds etc?) it maybe your router screwing up the higher frequency let me test on my computer (it has hdmi currently used) also what are you running Windows,Linux or Hackintosh if it's mac OSX some devices don't play nice on non apple computers (I tried to get my gpu to stop tearing the image no dice)
     
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  5. NekoMichi
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    NekoMichi Retro Collector

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    If the media devices are powered on but not outputting video via HDMI, then there is no interference. All devices are connected to the same power strip, although this problem only started today even though I haven't changed anything with the power supply. I'll try changing the channel later tomorrow, see if it fixes anything.
    2.4GHz is unaffected no matter if HDMI is active or not. I'm using MacOS, but it's connected to the network via Ethernet and not wi-fi. Other devices such as phones, Windows PCs and even the Switch lose connectivity to the 5GHz network when HDMI is active. Weirdly enough, the Mac is the only device that doesn't knock out the 5GHz network when plugged into the monitor via HDMI.

    If I activate any of the media devices but unplug the HDMI cable that connects the HDMI switch box to the monitor, the issue stops.

    EDIT: The HDMI switch box is passive and doesn't run off the power strip. Not sure if that helps.
     
    Last edited by NekoMichi, Sep 7, 2017
  6. Mikemk

    Mikemk GBAtemp Advanced Maniac

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    Try wrapping the wires in aluminum foil
     
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  7. Tom Bombadildo

    Tom Bombadildo SkyTom

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    I forgot
    Most manufacturers recommend avoiding using a power strip to power a router, it's possible that may be the problem. It can just come and go, I had a similar issue with a router back when I lived at my parents house and swapping to its own outlet fixed it.
     
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  8. NekoMichi
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    NekoMichi Retro Collector

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    Thanks everyone for the responses. Unfortunately, the issue is extremely persistent and has survived every other solution I've thrown at it. I've tried:

    - Changing channels
    - Connecting the router to a different power source
    - Connecting the router to a different power source and then relocating to 1m away from its original position
    - Lining the back of the shelf with aluminium foil so that it covers all HDMI lines

    It doesn't seem like a power source issue but then again it's also not related to LAN because even if I disconnect all Ethernet cables (including WAN) and just plug the router into power, the 5GHz network still drops out when HDMI is active.

    As a last resort, later I will be trying to relocate the router to an entirely different part of the building and see if that helps.

    UPDATE:
    Looks like moving the router completely away did the trick, although activating HDMI still makes me lose about 1-5 Mbps on the 5GHz network, at least it's useable.
     
    Last edited by NekoMichi, Sep 7, 2017
  9. NekoMichi
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    NekoMichi Retro Collector

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    Welp, 2 years later and I've finally solved it. Sort of.

    Turns out it wasn't the monitor, the multi-way switcher, or my monitor. It was my HDMI splitter. At the other end of the switcher, the splitter mirrors the signal to both my monitor and my Elgato. For some reason whenever an HDMI signal is passed through the splitter it knocks out my 5GHz network even though it's a wired device and isn't supposed to transmit any wireless signals at all. As soon as I remove it from the setup my 5GHz network works perfectly without interruption. This is what the device looks like:

    61XKvWitPHL._AC_UY218_ML3_.

    Also this only appears to affect channel 44, changing my 5GHz network to channel 40 allows it to function alongside the HDMI splitter without interference. Even though I tried this in the past without avail, it seems to work this time around.

    While the problem is now solved, I'm still perplexed as to why a wired device with no networking capability could affect a Wi-Fi router.
     
    Last edited by NekoMichi, Oct 23, 2019
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  10. Mikemk

    Mikemk GBAtemp Advanced Maniac

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    It probably has a wire coil or something acting as an antenna. Try wrapping it in a thick layer of aluminum foil.
     
  11. The Real Jdbye

    The Real Jdbye Always Remember 30/07/08

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    Alola
    Ever seen those warnings in instruction booklets and such saying something like "the device must not cause any interference and must accept any interference caused by other devices"? I figure this is what that's talking about. Your cheapo Chinese HDMI splitter hasn't gone through proper validation to ensure it meets safety standards and doesn't cause interference, and by chance it just so happens that it causes interference on the exact 5ghz frequency used by your router.
     
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  12. NekoMichi
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    NekoMichi Retro Collector

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    That's probably what's happening. When I received the item there definitely wasn't any kind of FCC declaration in the paperwork so chances are it's not been certified. Now I'm curious what else this device can interfere with.

    [cut to 2 days in the future when I get arrested for accidentally jamming police radio signals using a cheap HDMI splitter]
     
    Last edited by NekoMichi, Oct 24, 2019
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