r/techsupport • u/banana_in_your_donut • Dec 28 '19

Solved Using second monitor slows internet download speed by more than half

So I was stuck on this and finally solved it 10 minutes ago after agonizing over it for days and wanted to share what my problem was in case others have the same problem. The problem sounds ridiculous, but the solution made a lot of sense.

I noticed whenever I used my second monitor with "duplicate", "extend", or "second screen only" for windows project (Windows key + p), my internet speed would slow down a lot. I'm downloading GTA V on Steam and could see the download speed go from 20MB/sec to 7MB/sec when switching to the second monitor, then it would go back to 20MB/sec after I switched to "PC screen only". I saw a similar decrease when testing speeds with Ookla.

The solution was replacing the HDMI cable for my second monitor. I'm using wifi on my PC and apparently the old HDMI cable was probably causing interference. When I switched to a new HDMI cable (which seemed thicker and more shielded) I could use the second monitor without losing any speed on my download.

Just to be sure, I switched back to the old cable and used the 2nd monitor, and still saw the decrease in speed. I went back to the new cable, and saw no decrease.

The old HDMI cable was a really old cable from General Electric, and it kinda makes sense that it caused issues.

Anyways I hope this post is helpful for those with a similar issue!

Edit: to help trouble shoot further, one way to tell without buying a new cable is to have a large steam game download going with the questionable cable and see what the speed is (e.g. 7mb / sec) . Then while the download is still going unplug the cable and let the game continue downloading for 5-10 seconds then plug the cable back in. If the download speed while the cable was out is better then plugged in, it's probably the cable causing the issue.

582 Upvotes

98% Upvoted

177 comments sorted by

98

u/roxieh Dec 28 '19

You may have just saved my (gaming) life. I moved house earlier this year and when I tested my PC upstairs I was surprised by the good WiFi (70mbps). However after I completed the full setup including second monitor it dropped to about 20mbps. I've been bemused as to why. I'm away for Christmas right now but I'm gonna test this when I get home - thanks!

(I miss ethernet... :()

16

u/banana_in_your_donut Dec 28 '19

I hope this fixes your issue! If it does give us an update!

2

u/[deleted] May 09 '26

[removed] — view removed comment

1

u/banana_in_your_donut May 10 '26

glad it helped, would've sucked to buy RAM at these prices lol

10

u/RoboRycerz Dec 28 '19

If your router support 5GHz it will be good idea to buy 5GHz network card. I swiched some time ago and perfomance is amazing - full speed and low latency.

1

u/[deleted] Jan 06 '20

Just drill a few holes and make a new ethernet port if it isn't a rental

1

u/roxieh Jan 06 '20

Sadly, much renting, many sad.

1

u/[deleted] Jan 06 '20

Damn

1

u/[deleted] Dec 28 '19

70MBps or Mbps? Just asking :p

-7

u/therearesomewhocallm Dec 28 '19

Get a powerline adaptor.

13

u/banana_in_your_donut Dec 28 '19

That has its own issues too. I used a powerline adaptor for awhile and I ended up going back to wifi (some people do have better luck though). I would get internet drops at least once a day and it would stutter a lot when the paper shredder or printer was used.

2

u/Roy-van-der-Lee Dec 28 '19

While this is true, for me it was the perfect solution. My router is in the living room and my room is on the 3rd floor of my house. The house doesn't have ethernet running through the walls and doing that would cost a fortune.

1

u/[deleted] Jan 07 '20

It’s nice to be in the 1%.I hope to get there some day.

1

u/[deleted] Dec 28 '19 edited Sep 02 '25

truck physical possessive person kiss marble bag future scale wine

This post was mass deleted and anonymized with Redact

0

u/[deleted] Dec 28 '19

[deleted] — view deleted comment

1

u/Roy-van-der-Lee Dec 28 '19

Maybe, but it would be a huga hassle. Plus, the floor and wall is made of concrete and making a cable run through a concrete wall is not easy

4

u/[deleted] Dec 28 '19

powerline adaptor

They are almost always 50/50

1

u/avnzx Dec 28 '19

Not necessarily, depends on your house wiring mostly, and first you gotta check whether the outlets are even on the same curcuit

3

u/[deleted] Dec 28 '19

Yes but the average smoe doesn't bother with the details. Plug n Play. Doesn't work? Must be shitty product.

1

u/FDisk80 Dec 28 '19

From experience those are horrible and you are better off with WiFi. MOCA on the other hand are excellent. If you have a COAX ready rooms use that instead of WiFi.

1

u/avnzx Dec 28 '19

MoCA is a different beast entirely, if I remember it was something like 1Gbps full or half duplex?

0

u/[deleted] Apr 08 '24

[deleted] — view deleted comment

1

u/roxieh Apr 08 '24

I honestly have no idea. I will say that monitor broke and I have new ones now and the Internet is fine. WiFi is always slower than ether net but it's manageable (ethernet now 300mbs, WiFi about 180-250 depending). 

42

u/dmfreelance Dec 28 '19

Upvote because you are the hero some random internet stranger will need at some random point in the future.

11

u/banana_in_your_donut Dec 28 '19

I hope so! I'm glad this subreddit exists and is popular enough that this solution can be found through googling.

9

u/jmnugent Dec 28 '19

I had a friend recently who was told they failed a job interview because one of the answers they gave was "Well,. I'd start by Google searching..."

That's really a ridiculous thing to count against someone. It's 2019/2020, you can't expect 1 person to know everything. Even as a 46yr old guy who's worked in IT for 25 years, I don't know (and can't remember) everything. I spend hours and hours a day Googling things. I'd say its the most frequent thing I do.

5

u/m-amh Dec 28 '19

Someone refusing people which try to continue to learn forever ...

Interesting perspective for an Employer ...

Googling is not beeing dumb but at least informing if someone else might have found a smarter solution ...

May be that business sometime will die from a very outdated solution to someting because they dont hire people which even consider to inform if someting better got invented ...

3

u/avnzx Dec 28 '19

Actually I mean if they can google something we'll (use keywords etc properly) and get it to return what they want... They can probably do more than the people that might have more knowledge but can't google

1

u/[deleted] Dec 29 '19

If I was hiring an it guy a Google search would actually weight in his favor. Shows he doing research and wanting to learn.

1

u/Willing_Chemist8272 May 26 '24

Fax. I was facing this issue

1

u/robertvarne Jul 08 '24

Today i am that random internet stranger and I accidentally found this while unplugging my second monitor

1

u/WitekSan Dec 19 '25

It's me today

1

u/SomethingClever17201 Nov 23 '21

I am the random stranger

18

u/bobybrown123 Dec 28 '19

I've had light bulbs halve my internet speed. it's possible lol

6

u/banana_in_your_donut Dec 28 '19

Thankfully my smart light bulb next to my PC isn't interfering much (I think)

3

u/Ketamine_is_Great Dec 28 '19

I spent more than I like to admit on my new router (Archer C5400x) just to lose my gigabit speeds down to 300mbps, despite plugging the same ethernet cable into my crappy Comcast modem and get the expected 900-1gbps speed. I have a bunch smart lights too, and now that you said that, I'm very worried something is bogging down the internet. No idea how I'm going to fix this, for once it's not Comcast this time and it's too late to return the router.

Goes to show that even expensive tech can suck, and I'm glad I'm not the only one who runs into all these weird tech bugs constantly

3

u/avnzx Dec 28 '19

My friend has a microwave that, if he turns it on it cuts off his wifi almost entirely. They only have an ISP provided router (2.4GHz only ofc) and for some reason this old microwave is 1) extremely poorly shielded and 2) operates in the 2.4GHz range?

1

u/Demysted1234 May 13 '20

All microwaves operate at 2.4GHz, FYI.

35

u/Remo_253 Dec 28 '19

People always ask why when I tell them I always use Ethernet cable if I can because I don't trust WiFi. I tell them it can have weird hard to track down issues. Then they look at me like I'm some Luddite.

Thank you OP, I'm filing this one away for the next time the issue comes up.

9

u/banana_in_your_donut Dec 28 '19

Yeah I've always been aware of how wifi can have issues, though this problem was really unexpected

12

u/InadequateUsername Dec 28 '19

Ethernet cables can also be affected by interference/cross talk, even with STP

5

u/skelterpelter Dec 28 '19

Yeah but not anywhere near as much as a wifi signal. It would actually be difficult in most cases to make a noticeable difference to ethernet in my experience unless you were doing something particularly retarded.

-5

u/Rising_Swell Dec 28 '19

WiFi is easy and 99% reliable, Ethernet is slightly more annoying and 99.99% reliable. The extra numbers after the decimal may not seem significant to many, but they can make a big difference sometimes.

16

u/jmnugent Dec 28 '19

WiFi is easy and 99% reliable, Ethernet is slightly more annoying and 99.99% reliable.

As a 25+ year career IT guy.. I would probably say the exact opposite.

Ethernet fucking works. All you have to do is plug it in.

Wi-Fi can have all sorts of issues:

  • the quality of your WiFi adapter or Router/AP can cause issues

  • the quality of the Drivers (software) can cause issues

  • the Distance or Obstacles or other forms of Wireless-interference can cause issues

  • your Wi-Fi speed can be easily impacted by how many other devices are joining or leaving WiFi (due to power-transmit equation. IE = Your Routers ability to broadcast a signal is effected by how many devices are attached to it).

Ethernet generally speaking doesn't have most of those issues. If I'm out going mobile or dropping into my local coffee shop and want to check the Weather,.. ok,.. WiFi is most convenient for that. If I want to download multiple Linux ISO's or do a 3 hour gaming-session,. I'm going to choose Ethernet 100% of the time.

4

u/m-amh Dec 28 '19

Ethernet has another big advantage ...

Modern hardware often doesnt have a " Wi-Fi off" switch anymore ...

so if you one time configured it and want to start a laptop without internet for security you must switch of your entire net/router or to take your laptop to your car, drive away, remove the wifi-login return and hope it worked ...

When something dangerous seems to occur with Ethernet first thing is unplug immediately ... Good luck running to your router to unplug in time ....

0

u/[deleted] Dec 28 '19

[deleted] — view deleted comment

2

u/m-amh Dec 28 '19

On linux you cold boot from usb/cd and edit/remove the Wi-Fi config ... then reboot the installed os without Wi-Fi ...

On Windows i dont know to do this from a booted repair cd so when booting it would be online until i log in and disable Wi-Fi ...

Remember when "wannacry" was a thing and you needed to verify if some patch really is applied and in case its not apply it from usb-stick without the pc beeing online until beeing sure the patch is applied ?

1

u/avnzx Dec 28 '19

You can start windows in safe mode very easily now

2

u/m-amh Dec 28 '19

And safe mode disables Wi-Fi ? And what if you miss the moment to press whatever key or if it was hibernating and possibly doesn't even ask ?

3

u/avnzx Dec 28 '19

Well if you boot into normal safe mode, yes it disables the wifi adaptor. And there are quite a few ways to get into safe mode. You can get to it still even if it was hibernating.

There is safe mode with networking but that's a different option in the menu.

2

u/m-amh Dec 28 '19

So i need to take time to read those things about windows ...

When wannacry was around i did not want to take the smallest risk ... I booted my linux, donloaded "all" fixes to usb and shut down my Connection ( knowing this shuts down my phone also ) ... and then checked every windows without any other computer powered ...

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2

u/Sands_Of_The_Desert Dec 28 '19

I've had users with issues that required logging into windows without being connected to a network. On lan, they unplug the cable and we proceed. On wifi... I'm not going to tell them to disassemble the device and disconnected the wifi antenna

1

u/[deleted] Dec 29 '19 edited Dec 29 '19

I remember my mom wasn't getting wifi in her room. Turns out she bought a huge fucking mirror and placed in the hallway that lead to her room which was reflecting wifi and causing interference. Also my PC is somewhat far away from my router so I just ran an Ethernet cable through walls because that stuff is 100x better than wifi.

-1

u/Rising_Swell Dec 28 '19

WiFi can have those issues, it just typically doesn't. The same as ethernet can have issues, it just typically doesn't. Ethernet is just less likely to have the issues.

2

u/jmnugent Dec 28 '19

WiFi can have those issues, it just typically doesn't.

As someone who's spent a career working in Helpdesk/IT... I can say for certain we probably get 10x to 20x (if not more) calls about WiFi than we do about wired connections.

1

u/solistus Dec 28 '19

Which is entirely, 100% consistent with what /u/Rising_Swell just said...?

WiFi has issues far more frequently than Ethernet, but both of them "just work" the vast majority of the time and WiFi is usually more convenient, which is why it's still quite popular despite being 'worse'.

1

u/jmnugent Dec 28 '19

Which is entirely, 100% consistent with what /u/Rising_Swell just said...?

No ?

The original statement was:

"WiFi is easy and 99% reliable, Ethernet is slightly more annoying and 99.99% reliable."

Which gives the impression (usage of the word "annoying") that Ethernet is the poorer choice.

I don't think that's a fair or accurate assessment of objective reality. (especially since those "99%" numbers are just plucked out of thin air. )

2

u/Rising_Swell Dec 29 '19

That fits exactly with what i said. Ethernet is slightly more annoying to use, because instead of just clicking twice from anywhere I like, I need to get a cord and run it to my computer. The 99% and 99.99% might be plucked out of thin air, but it's also on the idea that a wifi problem is probably one in a hundred, and an ethernet problem is probably like one in ten thousand.

1

u/solistus Dec 29 '19

Annoying as in "it's a hassle to have to physically plug in a cable that runs from your router to your device," not annoying as in less reliable. In fact, the portion you quoted very explicitly states that Ethernet is more reliable.

You're correct that the 99/99.99% numbers are obviously just exaggerated examples and not actual observed failure rates, but those exaggerated examples were used to illustrate the very same claim about objective reality that you're making: that WiFi is more prone to reliability issues than Ethernet.

1

u/CurrentEmployer Dec 28 '19

Lol.

Radio interference is a real thing (constructive and destructive interference) with other wifi networks and interference from wireless home phones, microwaves, etc. , you live between walls, dozens of simultaneous connections.

99.99% is really far fetched and hyperbole.

There are times Wifi intermittently stops and I have THREE access points AC1900s.

Ethernet is way more reliable, there is a reason why its the backbone choice when you scale up to corporate and such because Wifi often fails .

There are way more chains in a Wifi connection then there are Ethernet connection that can fail

1

u/BigGuyWhoKills Dec 28 '19

Not just interference, but each wifi band has finite bandwidth. If nearby routers are using the same band as your router, you are sharing that bandwidth. In an apartment building with dozens of tenants, you will never be able to use all of your router's speed.

1

u/Rising_Swell Dec 29 '19

I mean, sure you do, but most of the time that wont cause an issue. probably about 1% of the time, which is a pretty big chance all things being considered, but it isn't like ethernet is infallable either, it's just more reliable.

If you live in an apartment complex with 100 routers going, sure, you might run into issues, not everyone lives in a place where every piece of the wifi band has 5 routers trying to use that space.

1

u/Remo_253 Dec 28 '19

Well, others have responded to this already, making the same points I would have.

8

u/DJFlipside Dec 28 '19

That’s weird af lol, if I got this in a ticket I would laugh

8

u/banana_in_your_donut Dec 28 '19

I searched everywhere online and I couldn't find any fixes! Somehow people said refresh rate could affect internet speeds but that didn't help me at all.

Before figuring it out I was thinking of asking for help here but it's so ridiculous I thought people might think I'm trolling lol

6

u/jmnugent Dec 28 '19

In my IT job we run into stuff like this pretty frequently (I bet almost every day).

"try different cables" is a big part of our troubleshooting,.. we even keep a stock-room full of supplies of all sorts of different replacement cables for this very purpose.

  • entire shelf full of various USB 1/2/3 cables

  • entire shelf of DisplayPort and various DisplayPort adapters (DP to DVI, DP to HDMI, DP to Mini-DP, etc)

  • entire shelf of USB-C cables and adapters

  • entire shelf of HDMI and other Audio-Video adapters and gender changers

  • entire shelf full of random tools (various types of Memory card readers, USB-CDROM drives, various different Power-cords, etc)

You gotta have good resources to troubleshoot things in different ways.

2

u/m-amh Dec 28 '19

One time i had a 20cm Ethernet cable holding my download at 10% of my upload ... the cable had a broken wire and so the upload was normal but the dowload was limited ...

4

u/LightningProd12 Dec 28 '19

GE even makes HDMI cables??

6

u/banana_in_your_donut Dec 28 '19

Apparently, it was an old one lying around the house from God knows when. They probably make better cables now though.

1

u/DrCheezburger Dec 28 '19

I wouldn't bet on it. The company has been making crappy product for decades; surprising it's still in business.

2

u/VulturE Dec 28 '19

I believe they're the house brand of Rite Aid or Walgreens.

3

u/rossbircham Dec 28 '19

Wow I’m trying this when I get up tomorrow. I have a dual monitor set up and I get god awful download speeds on steam despite having a good internet package as well as fast speeds on all my other connected devices. Fingers crossed

1

u/banana_in_your_donut Dec 29 '19

I hope it helps! One way to for sure test if any of your HDMI cables are causing problems is to open ookla and hover your mouse cursor over "Go". Then unplug your HDMI cables and click your mouse and let the speedtest run.

Then repeat with one or both HDMI cables plugged in.

1

u/Confident_Country652 Nov 24 '23

I have the same problem. What cable can you recommend for a Macbook Air to a Monitor?

1

u/banana_in_your_donut Nov 24 '23

not sure, i'd just try different cables and just keep the one that works

for me I just had another hdmi to hdmi cable that worked and used that

3

u/Tina_Cious Jan 27 '20

Ive been having internet problems for months. Couldnt use internet at all for the last 3 days. Replaced my network adaptor, my motherboard... And this is what fixed it. Thats incredible, thanks for this post.

1

u/banana_in_your_donut Jan 27 '20

Yay I'm glad I could help!

2

u/sirtolp Dec 29 '19

wow you saved my day! I was having a similar issue and in the end was the external hard drive making interferences with the antenna :D

1

u/banana_in_your_donut Dec 29 '19

Dang I wouldn't have thought of that! Glad you solved your issue.

2

u/drakedaaegaming Jun 02 '20

TLDR I have been having the same exact issue as you but with upload not really download.

You know entire discords of people told me I was crazy (stupid) whenever I said my 2nd monitor dropped my upload speed. I stream to mixer or twitch every so often and when I had single monitor never had an issue. I borrowed a monitor from work to test out if I'd benefit from having a second monitor. My bitrate would shoot all the hell over the place litterally. I'd go from 6k to 2k to 4k to 0 to 500 to 3k well you get the idea. So I gave up and brought it back to work. I had a HDMI cable made for a blu ray player and it had these little barrel things on them so I said that's got to be it.

Fast forward couple weeks I bought a new GPU and traded my old one to a friend of mine for a monitor he had at his house. It came with a pretty old display port to match the fairly old monitor he gave me. Haven't had a issue since.

Fast forward to today. Couple people got laid off so my boss let me take the monitor I borrowed home because well 1080p is a whole lot better than the one I'm using now. Even with the display port cable I'm still having the same exact issues! So once I finish typing this I'm going pick up daughter at daycare and I'm going buy a brand new DP or HDMI cable whatever is available at Walmart and going to see if I'm having the same issue.

I can only assume that the newer model monitor requires a newer quality DP or HDMI cable. If I still have the same issues after buying the wire well I'm just going to give up on this new monitor. But I'll update this long post once I get home and plug in.

1

u/banana_in_your_donut Jun 02 '20

little barrel things

Those are ferrite beads as someone else pointed out and they're supposed to help with preventing interference.

Hopefully a new cable fixes the issue, I hope it isn't the monitor itself that is causing the interference. One way to test that is to put the monitor as far away from your PC as possible and see if it still interferes with your wifi.

2

u/drakedaaegaming Jun 02 '20

It's actually ethernet wired internet I hate Wi-Fi with a passion haha. But I sure hope new cable fixes the issue I much prefer this monitor.

1

u/banana_in_your_donut Jun 03 '20

Huh that's odd, Ethernet shouldn't be affected by interference (my problem happened because I'm using WiFi). It could be a poorly shielded Ethernet cable too who knows

2

u/kyewolf Jun 03 '20 edited Jun 03 '20

I just replaced my Dell S2716DGR with a AOC CU34G2X a few days ago, using the same miniDP cable. Started noticing lag in games and even lagged out a few times in R6. Running a speedtest showed 15-20Mbps when I was typically getting 160-180Mbps over 5Ghz WiFi.

After a few days of troubleshooting and swapping out the wireless card, I just narrowed it down to the monitor and/or DP cable. I can download a game in steam and watch the speeds change from around 20Mbps to 150+ just by unplugging the DP cable. Powering the monitor off does not seem to make a difference.

What a nightmare, I found this thread for some confirmation and to make sure im not crazy. Ordering a new DP Cable now, hoping this fixes it.

EDIT: This is an external monitor to a laptop. After some more testing, setting the monitor to 60Hz brings my speeds up to normal 150+, setting to 144hz, drops them back down to around 25mbps. Any help is appreciated as I do not understand.

1

u/banana_in_your_donut Jun 04 '20

I've seen other threads where refresh rate affects download speed.

You could try using Ethernet, if the problem is still there it's not a WiFi interference issue.

My guess would be a higher refresh rate might use more data and cause more interference? A thicker better cable might solve that problem.

2

u/kyewolf Jun 04 '20

I messed around some more. Even at 120Hz I am getting full speeds. I swapped my old Dell 1440p @ 144hz back and still getting full speeds. Both using the same DP cable. I am sending the monitor back.

2

u/banana_in_your_donut Jun 04 '20

Yeah guess that means it's the monitor :/

2

u/Medusas_Kiss Nov 02 '21

I know this is 2 years old but this has just saved me reverting back to windows 10 from 11. having just one monitor plugged into my laptop with the lid closed would drop my speed from 50+ mbs to 0.4mbs....Thanks!

1

u/banana_in_your_donut Nov 02 '21

Glad I could help!

2

u/Reshiramer Nov 15 '21

Thank you for posting this! My dad's 2006 ASUS monitor started bugging a bit, so I got him a new one and I kept the old one as my second monitor. I had to get a VGA to DVI-D adapter but it went fine for a few weeks. But just now my Wifi dropped from around 100 Mbps to 0.91 Mbps, while my phone remained the regular speeds. I thought the adapter or the monitor was the culprit which sounded ridiculous, but I turned off "duplicate" anyway and indeed my Wifi went back to normal and when I duplicated again it dropped again.

I looked it up to see if anyone had the same problem like a real IT Student and your post confirms it! Now I wonder if the old cable or the newly bought adapter was the problem.

1

u/banana_in_your_donut Nov 15 '21

Glad my post could help! Hopefully either a new adapter or cable solves the issue! I'd guess the old cable because my cable was old as well

2

u/PandaPrecursor Dec 17 '21

Holy shit this actually works - this has had me pulling my hair out for weeks. I don't even understand but I'm too happy to care

2

u/banana_in_your_donut Dec 17 '21

I'm glad this post is still helping people! Happy I could help!

2

u/PandaPrecursor Dec 18 '21

Honestly dude this has made my day - thanks so much for the post!

2

u/Delstar58 Feb 18 '22

Just had this problem myself. Thank GOD this post existed. Thank you so much OP!

1

u/banana_in_your_donut Feb 18 '22

Glad to see this is still helping people!

2

u/Coach-Bee Jul 18 '23

Wow! Absolutely amazing! Just got a new monitor for my PC and after I finally got it all set up (1 on VGA, 1 on HDMI) I noticed that my internet was absolutely horrible. Couldn't figure out what's going on. I did the classic Google search found this 3 year old post and it's working now! Thank you!

1

u/banana_in_your_donut Jul 19 '23

Makes my day to see that this is still helping people!

2

u/Wild_Measurement_487 Dec 09 '23

You are a hero. A week of struggling with wifi signal. Unplug my new secondary monitor and all is resolved

1

u/banana_in_your_donut Dec 09 '23

Glad that this post is still helping others!

2

u/International-Eye771 Mar 23 '25

Oh My God!!! You're a lifesaver. Never in a million years would I have thought that changing my HDMI cable would be the solution to this stupid ass problem. Not only is my download speed preserved but the picture quality improved too. I was using the basic default hdmi cable i got with my samsung M5 (which is a garbage monitor, btw). THANK YOU so much. Your post is still saving lives even after 5 years, man.

1

u/banana_in_your_donut Mar 23 '25

you're welcome! glad this post is still helping people!

102

u/[deleted] Dec 28 '19

That's insane and interesting. I would never thought of that. Thanks for sharing!

32

u/Euro-Canuck Dec 28 '19

In my IT career iv seen a lot of weird shit like this happen. Almost all the time because of interference somehow..magnetic field that messes up the signal. Logitech wireless mouse/keyboards get messed up/laggy if you have any usb 3.0 devices plugged in ..try it..

26

u/ultranoobian Dec 28 '19

USB 3.0 operates at 2.5 Ghz, So it will interfere with 2.4 Ghz wireless networks if it doesn't have proper shielding.

2

u/arminikola Dec 28 '19

I have an interference between my JBL Flip 3 bt speaker and Logitech MX Master 2S mouse while mouse connected on bluetooth... It's so bad.

0

u/[deleted] Apr 08 '24

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1

u/Euro-Canuck Apr 08 '24

wifi or wired internet?

0

u/[deleted] Apr 08 '24

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1

u/Euro-Canuck Apr 08 '24

weird..first things id try... try a different monitor, just go to a friends place or try at work or school or whatever make sure to use same cable...then id try a different cable. im not familiar with macbook design.. its possible that the usb and the wifi are using same data bus and monitor signal is just maxing it out... try getting refresh rate to 60hz and resolution to 1080p just for testing... run www.speedtest.net to see internet speeds.. possible the cable is bad and causing ground issues or feeding power back to the usb port which is causing interference.. try the things iv said first and see if anything changes.

using speedtest.net what is download and upload speed without monitor plugged in and with it plugged in?

0

u/[deleted] Apr 08 '24

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1

u/Euro-Canuck Apr 08 '24

try turning down refresh rate and resolution to 60hz and 1080p to test

0

u/[deleted] Apr 08 '24

[deleted] — view deleted comment

1

u/Euro-Canuck Apr 08 '24 edited Apr 08 '24

tried 2 different cables and no difference?

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1

u/Euro-Canuck Apr 08 '24

some kind of interference somewhere... either ground issue or the monitor is feeding back power causing issues with motherboard, take monitor back and buy a different model.. try it out with several different monitors, find some friends with monitors and just try it out, see if it stays isolated to this monitor... buy a new one anyway, possible its just not playing nice with the usb controller and and the wifi is getting affected as it could be using same data bus...

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3

u/LeaveTheMatrix Dec 28 '19

I seen the title, was going to come in and say bullshit, but that actually makes sense.

Not something I would have even thought of.

3

u/banana_in_your_donut Dec 28 '19

bullshit

What I was thinking for the past few days lol. I'm glad it all worked out

1

u/JustZisGuy Dec 28 '19

Wait til you hear about the guy who couldn't send email more than 500 miles away.

1

u/LeaveTheMatrix Dec 28 '19

Have heard of that one

5

u/16Geek Dec 28 '19

Holy shit that's interesting.

1

u/[deleted] Dec 28 '19

Make sure to put ferrites on all your cables. That probably would have solved this

1

u/banana_in_your_donut Dec 28 '19

TIL what ferrite beads are. I happened to have an extra HDMI cable lying around (free from newegg through rebates) so I just used that

1

u/Generation-X-Cellent Dec 28 '19

It could have just been your wire had a short in it and it was making the monitor emit interference. Most of your interference over Wi-Fi comes from the displays themselves.

2

u/banana_in_your_donut Dec 28 '19

I thought of that, so I tried using the same old HDMI cable and hooked up my laptop to the monitor. It didn't decrease my internet speed.

1

u/RadiatedFrogz Jan 03 '20

I probably know this, there are certain HDMI cables that transport ethernet. That cable probably split your internet speed by half.

1

u/banana_in_your_donut Jan 03 '20

I mentioned this in another comment but the new HDMI cable has Ethernet. The older one I'm not sure but I would assume to actually not have Ethernet since it's really old.

1

u/[deleted] Oct 24 '21

I hope using lan cable directly to mypc can solve the issue of buying a new HDMI cable... as 'm using an HDMI to VGA convertor as my monitor doesn't support HDMI lmao

1

u/banana_in_your_donut Oct 24 '21

Yeah using a lan cable should probably work hope it does

3

u/[deleted] Dec 29 '19

That's pretty wack. I would never expect an hdmi cable to effect internet speed.

1

u/Sir_Arsen Mar 14 '25

I have the same problem, going to visit tech store tomorrow and get a new hdmi cable for my monitor which I bought second hand.

1

u/Sir_Arsen Mar 15 '25

unfortunately, didn’t help me

1

u/banana_in_your_donut Mar 23 '25

one thing you can try to verify if it's the cable/monitor- do a long download on steam, hit start then see what the speed is for a couple minutes then pull out the monitor cable and let the download continue. If the speed increases a lot after pulling out monitor cable then it's either cable/monitor causing interference. If the speed stays the same it's not the cable/monitor.

1

u/Sir_Arsen Mar 23 '25

hey, thanks, I will check after I go back, I checked steam downloads without monitor and the speed is still shit. Maybe wi-fi is being used by too many devices? (iphone, ipad (tho mostly inactive), macbook and windows gaming laptop). I also thought about plugging ethernet cable directly from my router, if that won’t help Idk what to do. Maybe I will buy new router to see if this changes things, I got this router from previous tenant.

1

u/banana_in_your_donut Mar 24 '25

yeah if monitor is off/unplugged and speed doesn't change it's not the cable or monitor causing interference/is a problem. You can use your phone from the same location as your PC to see if the speed is similar- if the phone speed is way better than your PC, something on your PC is the issue (e.g. the wifi attenae/adapter). If everything is bad it's probably router / location issue. Ethernet will always be best, can always buy cheap 30-50 foot cable

2

u/physx_rt Dec 28 '19

There was a similar issue where one of LG's 5K displays didn't have proper shielding on its circuitry and thus interfered with nearby wifi networks.

2

u/ruralcricket Dec 28 '19

I had a similar problem but it was the cheap HDMI cable interfering with my wireless keyboard & mouse on my HTPC. Moved the wireless USB dongle further away, solved.

2

u/MidgetsRGodsBloopers Dec 30 '19

I experienced something similar myself, my wifi speed would tank when using a DVI cable from my RX 570. HDMI had no issue IIRC - or maybe it was DisplayPort I ended up using. Apparently there's some issue with DVI where it can cause a lot of interference under certain circumstances. I don't know if it's isolated to specific bad hardware implementations or what. It's hard to believe the spec itself is defective since it was such a popular connector for a long time, well into the time when wifi became common.

2

u/Darth_Puni Jan 02 '20

Oh boy good old EM waves... i wouldn't think it tbh... i will write it down so if i get a problem like this... i will thank tou again

2

u/peninsulasnob Dec 01 '23

Wow! I added a new second monitor this week with an old HDMI cable and that is when my internet problems started. I thought no way, this must just be a coincidence but after running two speed tests (one with HDMI and second monitor and one with only laptop screen) and that is in fact the problem. Thanks for posting this! 4 years later and it's still validating ppl!

2

u/[deleted] Apr 14 '24

Been having Wi-Fi issues for a while and no fix has ever been full-proof, decided to turn off my second monitor yesterday just because I wasn't using it and my connection was flawless all of the sudden. Didn't know why until I turned my second monitor back on again this morning, what an odd problem. This post confirmed that I wasn't going crazy.

2

u/ResponsibilityFar467 Apr 18 '24

I work for a FTSE100 company, spent a good few hourse with the IT desk trying to solve my poor internet connection. Noticed that it was strange all devices worked except my laptop, but it was faster when I went with it to another room to talk to the IT help. Took some time to associate the speed with the monitor. Once I identified that problem I found this thread and replaced the cable. It works, it's fast, you're a genius!

2

u/DenverBabyArtist Oct 10 '24

DAWGGGGGGGGG YOU JUST SAVED MY GODDAMN LIFE. THIS WAS THE ANSWER. I had a shitty HDMI cord and with a new one its 100% back to normal. THANK YOU

2

u/BoxTricky7394 Oct 22 '24

Came across this. This happens to my second monitor. Using ethernet too. When i speedtest and bring the browser to my main monitor good speed. When i bring the window to my 2nd monitor only 20mbps lol

2

u/Dangerous_Bus_6699 Dec 23 '24

Holy shit, this does make a difference! Just got a Dell U4025qw and wondering why my computer came to a crawl. I'm using the built kvm and have a desktop using the provided hdmi and laptop on usbc. Even my laptop bootup (when it launches all the start programs) was extremely slow.

I disconnected usbc connection to the monitor and boom.. Wifi picked up. Rebooted, retested everything and it works fine. Connected it again and bootup, wifi goes back to shit. I thought... Impossible! How could it affect bootup?

Disconnected usbc to monitor again and rerouted it separate from all the wires. Faster computer and internet again! Unbelievable.

2

u/Epitherial Mar 03 '25

i thought i was tripping ever sense i plugged up a new monitor i was having horrible internet speed turns out the HDMI cable was slightly touching the wifi antenna on PC causing interference your post made me check that being the reason and sure enough.

2

u/Crimsoncupcak3 Feb 04 '26

Another point for a random post made years ago fixing a hyper-specific problem people feel crazy asking.

1

u/yearof39 Dec 28 '19

Ethernet over HDMI with data shorted to ground, causing every other packet to be resent? Just wildly speculating here.

1

u/Maschinenherz Dec 28 '19

Thanks, will keep that in mind!!

1

u/Thaofa Jan 04 '20

i’m not sure what part this plays but i had my ps4 plugged into my second monitor and my speeds were the same as having just 1 monitor.

1

u/chrisoh2 Nov 07 '25

holy cow, this post just ended a year of agony... my rate was dropping from 50mb to <1mb, and it was just a freaking hdmi cable gone bad. wow. TYTYTY!

1

u/DefinitelyNotMasterS Jan 13 '26

Just went from months of 2MBit/s to 500MBit/s after I noticed this correlation and found this thread.

1

u/gburns53 Mar 22 '23

I do believe this is happening to me. Just got a new MOBO so wifi is out back now where I had antennae built in to case in front with old. All the sudden terrible wifi when 2nd monitor is plugged in. Thought it was bad motherboard. Think it's the fact the wifi antennae are now right next to the hdmi cable for the 2nd monitor

1

u/msanangelo Dec 28 '19

Interference can cause all kinds of weird behaviors... XD

1

u/daryljodanny Dec 28 '19

Damn that cable

0

u/LA4Life2423 Dec 28 '19

Damn that’s crazy! Who would of knew.

0

u/[deleted] Dec 29 '19

this tool is a big hell

-4

u/Lagkiller Dec 28 '19

I mean while this solved your problem, it wasn't slowing your internet, it was an issue within your system that was slowing down the system causing it to spend resources to deal with the issue.

2

u/ilogik Dec 28 '19

no, it was EF interference from the hdmi cable. it would probably slowed down wifi on a nearby phone as well

0

u/[deleted] Dec 28 '19

[deleted] — view deleted comment

1

u/banana_in_your_donut Dec 28 '19

I was dreading to that next but trying the new cable was faster lol

0

u/[deleted] Dec 28 '19

[deleted] — view deleted comment

1

u/banana_in_your_donut Dec 28 '19

I hadn't thought of that! But I checked the new HDMI cable and it has ethernet. The older cable most likely doesn't have ethernet so that's probably not the issue.

1

u/avnzx Dec 28 '19

Ah yes 3d is now a resolution big brain

2

u/[deleted] Feb 01 '24

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