Macbook Pro wi fi slows down when connected to external monitor

Why do I have difficulty with Wi-Fi or Bluetooth devices when USB 3 devices are attached to my computer?



Some USB 3 devices can generate radio frequency interference that can cause Wi-Fi and Bluetooth devices operating in the 2.4GHz band to have issues communicating with your computer. Here are some tips to avoid this issue:

• If your USB device has a cable long enough that you can move the device, place it away from your Mac—and make sure not to place it behind your Mac, or near the hinge of its display. The antennas for Wi-Fi and Bluetooth are located there, and USB 3 devices placed there might interfere with your wireless connections.

• If you're using adapters or dongles on a Mac computer with Thunderbolt 3 (USB-C) ports, plug them into the front port on the left side of your Mac, or into the ports on the right side (if your computer has them). These ports are the farthest away from the antennas, making interference less likely.

• To avoid interference on the 2.4GHz band using Wi-Fi, try using the 5GHz band instead. You can change this on your wireless base station. Bluetooth always uses 2.4GHz, so this alternative isn't available for Bluetooth.

from:

About USB on Mac computers - Apple Support

Resolve Wi-Fi and Bluetooth issues caused by wireless interference

Resolve Wi-Fi and Bluetooth issues caused by wireless interference - Apple Support

The actual problem is, lid closed or not. I am facing same issue and problem is noticeable when you close the lid.If you keep open the lid and make the external monitor as main display, you will not face that issue.

Connection of an external display is a Big Deal Internally. It creates a non-trivial level of memory-fetching activity inside your Mac. However, almost all of that increased activity is handled by the display-generator Hardware automaton. Simply connecting/activating a display does not impact processor utilization OR Wi-Fi performance in the way you report.

The "stock answer" was provided to help you think about your peripherals. USB 3 and USB-C Hubs are well known generate 2.4 GHz interference, and a model that is poorly shielded can be a problem.

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There is one older report of a display that generated so much Radio Frequency Interference (RFI), it would knock a NEARBY router off the air. The problem was quickly detected and recalled.

what Make & Model display is yours?

• LG-display recall -- to address Wi-Fi interference so severe, it knocks the Router off the air if too near the Router.

https://9to5mac.com/2017/02/03/lg-fixes-wifi-interference-problems-with-ultrafin e-usb-c-5k-display-new-units-unaffected/

if you hold down the Option key while you click on the Wi-Fi Icon on the menubar, you get a snapshot of current wifi operating parameters, like this older one. Please screenshot, photograph, or transcribe yours, so we have an idea of how your Wi-Fi is working. If you can do before and after, that would be even better.

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I strongly disagree.

As has been suggested above, a badly-shielded display cable could easily impact ONLY the MacBook Pro Wi-Fi, whose antennas are located along the back hinge.

no display:

Noise: -90 dB

yes display:

Noise -79 dB

that's a logarithmic scale. That noise is so strong some users are attempting to use a Signal level at -79 dB (it just misses, with -75 dB being too just weak to be stable. Signal strength RSSI and Noise are near-instantaneous measurements.

(Note: I am not certain you allowed your samples to stabilize before reporting. The [smoothed] Transmit rate with display active is higher than the Transmit rate with no display.)

so presumably you connect that display Directly to your Mac with an HDMi cable, Not through an adapter, is that right?

HDMI was invented for HD TV sets. it works great at its original resolution of 720i or 720p. At higher resolutions, it quickly develops issues that are complex to solve, and the cables and adapters required to solve are NOT intuitive.

HDMI cables you want for HDMI-only Displays (higher resolutions than 720p TV sets) are marked as Certified with an anti-counterfeiting tag and are labeled:

"Premium High Speed HDMI cable" or that + "with Ethernet" --OR--

"Ultra High Speed HDMI cable" or that + "48G"

Cables with No Certification tags are good for your standard 720p TV set, and not much more.

Cables that "shipped in the box" are often 'lowest bidder' cables, and are a known source of a broad range of issues.

<< I have not tried a premium HDMI cable, they cost a lot. >>

in the US, this reputable vendor has ultra cable for not much money. you should be able to find one as well.

Monoprice 8K Certified Ultra High Speed HDMI Cable - HDMI 2.1, 8K@60Hz, 4K@120Hz, 48Gbps, HDR, VRR, CL2 In-Wall Rated, 6ft, Black Product # 42674 - US$7.99

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A quick solution is to use 2.4 Ghz band from your router (if available) when faced with this issue.

5GHz connections already known to have trouble with obstacles like walls and steep angles, and whatever the display port is doing is just adding to the signal trouble thus resulting in wifi blackout.

May be Apple should look into hardware design to solve it.

Thanks

if this is a specific third-party display that is causing the problem, the issue is already identified.

That third-party display is creating Wi-Fi interference so strong, it cuts your internet speed in half.

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At the highest resolutions, the CABLES required to run these displays are not trivial.

what display(s) are being used?

what connection methods are being used?

In my case the problem was that my desk was setup in another room than the router, and I faced this issue only when I connect the external monitors.

What started working for me that I accidentally placed my MacBook's lid at an obtuse angle ~120 degrees while being on the 2.4 GHz network. 5 GHz still behaves the same and is see the issue.

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Its a Dell Monitor, and the best part that rules out everything else is this...

On the same desk I tested with a ThinkPad running Ubuntu and another HP Laptop runnign Windows.

Now everything is same, same Distance, same Monitor, same Cable, same Internet Router.

Internet signal/speed has no issue whatsoever in ThinkPad and HP Laptop when connecting external display!!

So I guess it puts spotlight on this really being an Apple issue, isn't it?

kulgod007

please start a NEW discussion with your particulars. This discussion is already complex and you are adding nothing by your additional (and slightly different) complaint. You are just making things more confusing.

If you wish to follow what happens here, just click the title 'subscribe icon'.

My complaint was that another reader, kulgod007, tried to hijack your thread. In direct response to what they wrote, I tried to send them away so we could keep working on your issues.

Have you tried a "Premium" certified HDMI cable?

any difference?