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2013 MBA Wi-Fi very slow when AC adapter is plugged in?

WiLLGT09

WiLLGT09

macrumors regular
Original poster
Nov 13, 2007
213
29
I've come across a strange problem today. I recently rearranged my computer setup to a standing desk in another room, which in fact is even closer and in direct line of site to my Apple Airport Extreme. I noticed once yesterday, after setting everything up and once again this morning when I woke the computer from sleep, that my internet speed was horrifically slow (2.88 MB/s as opposed to the 50+MB/s I normally get). In the same location, on the same 5GHz wifi network, I ran Speedtest on my iPhone 5S and got the 50+MB/s I was expecting. Now I've been using this exact same setup (External Monitor, Apple BT keyboard & mouse and Belkin Thunderbolt dock) in another room, with no problems with internet speed -- all while plugged into the AC adapter of course.

I've gone through a bit of trial and error: unplugged everything and use the MBA on the couch - fast internet. Later, I had everything plugged in on my standing desk and tried a series of steps:
  • opening screen from clamshell mode (slow internet)
  • keeping everything plugged but moving MBA closer to router (slow; ext monitor not causing interference, I assume)
  • unplugging Thunderbolt cable but leaving AC adapter in (slow internet)
  • then unplugging AC adapter (fast internet).

What?!

Now, if I then plug the AC adapter back in, my internet seems fine. I'm typing this write now, all plugged in, and just got 56+MB/s down.

The only thing that's really changed in all this is the electrical outlet I'm using with my surge protector/power strip. Could that be causing an issue? Otherwise, I'm not sure what's going on, considering everything's fine after re-plugging in the AC adapter.

Thanks!
 
There are things that only happen when plugged in and on wi-fi, updates, apple match, genius updates, backups, iPhone backups, etc...

This should quiet down over time.
 
bit density said:
There are things that only happen when plugged in and on wi-fi, updates, apple match, genius updates, backups, iPhone backups, etc...

This should quiet down over time.
Click to expand...

Yeah, but months and months of this setup plugged in at another desk (on another AC outlet) with no issues? Still seems odd.

Also, as for this morning "iTunes match, genius updates, backups, iPhone backups" would not be occurring, as iTunes was closed, my Time Machine drive is not plugged in and nor is my iPhone.

Thanks!
 
Thanks. I did some brief searching, but nothing related really popped up. If you can find the thread (despite not having a solution), I'd love to read it.

Side note: Wi-Fi still going strong now. I have Wireless Diagnostics monitoring running right now, so we'll see if anything pops up.
 
Boyd01 said:
I think this is it. Sorry, close but not the same. This thread had to do with wifi vs external disks.... https://forums.macrumors.com/threads/1695154/
Click to expand...

Thanks! I do have a USB 2.0 hard drive attached to the USB 3.0 port on the Thunderbolt dock...but when I first experienced this (though not this morning), I did have my iPad attached directly to one of the USB 3.0 ports on my MBA. Maybe that's causing some issues?

However, that thread mentions and this article says that:
"...there are interference issues between USB 3.0 and the 2.4 GHz band"
Click to expand...

But, both my MBA and iPad use my Airport Extreme's 5GHz network, so I wouls think there wouldn't be a problem?
 
I do not have an AAE but my Netgear router has shown some funky behavior from time to time. After doing some research I found others that had similar issues and it appears that it is simply radio interference.

Changing the channel on your wireless network to a fixed channel rather than auto fixed the issue for me. You will have to go through some trial and error to find the best channel but start high and see how it works.
 
troutspinner said:
I do not have an AAE but my Netgear router has shown some funky behavior from time to time. After doing some research I found others that had similar issues and it appears that it is simply radio interference.

Changing the channel on your wireless network to a fixed channel rather than auto fixed the issue for me. You will have to go through some trial and error to find the best channel but start high and see how it works.
Click to expand...

Ah, thanks. I had manually set the channel for the 2.4Ghz network, but for some reason left the 5GHz on Automatic. I've just changed the setting to a static channel (161). We'll see how it goes. Is there a particular channel that's better? I guess I could do a process of elimination if need be, but I've alway felt like I'm just picking one at random?
 
WiLLGT09 said:
Ah, thanks. I had manually set the channel for the 2.4Ghz network, but for some reason left the 5GHz on Automatic. I've just changed the setting to a static channel (161). We'll see how it goes. Is there a particular channel that's better? I guess I could do a process of elimination if need be, but I've alway felt like I'm just picking one at random?
Click to expand...

Unfortunately it is just a guessing game. Start at an upper channel and do a speed test and see if it is what you were use to getting. If not, go low, test again, go middle, etc. You'll find the sweet spot.

I simply got lucky when I did mine but I have a lot less channels as well.
 
As weird as it sounds if I position my computer a few degrees off axis, the link speeds with drop to like 2Mbps whereas one position it will connect at something like 550Mbps. It's confusing me to as well, though I do not have a line of sight to the access point.
 
OK, I just experienced this now. I woke my computer after being asleep overnight. I ran a SpeedTest after a few minutes: 2.79 Mb/s down, 0.75 Mb/s up, 378 ms ping -- terrible.

Then I unplugged the ac adapter, and immediately put it back: 57.59 Mb/s down, 11.62 Mb/s up, 9 ms ping -- Excellent.

This is very bizarre.

EDIT #1: Ok, I've been able to replicate the issue again. I let my computer sleep for about 10 minutes or so, and swapped AC adapters. I had been using my old MacBook Pro power cord with the MagSafe 2 adapter (this is the same power cord I've been using for months at my old desk with no issue). Nevertheless, to rule out any power adapter oddness, I used the standard MBA ac adapter, and I still experienced the issue: wake computer, slow internet, unplug and re-plug ac adapter (or disconnect the laptop from power -- I unplugged and re-plugged the surge protector), now have fast internet again.

It seems odd that it also seems somewhat related to waking the computer from sleep, but again, this is an issue I've never experienced prior to moving my desk.

Also, while this is the same surge protector I've been using for months and months at my old desk, could there perhaps been some issue with that? I've also used this particular outlet in my apartment before to charge my MBA with the regular MBA ac adapter, though not using the surge protector, and never experience this Wi-Fi problem before.

EDIT #2: Ok, did another little test this morning. Let my mac sleep a bit again, but unplugging everything except the power cable and moving it away from the standing desk and onto the couch. After bout 10 minutes or so, I wake the computer, leaving the power adapter plugged in, and the Wi-Fi speed was excellent. I'm guessing, for whatever reason, I'm getting some strange interference, probably from the Samsung LCD monitor I'm using (even though it's not sitting in between the computer and the router.)

The only other thing I can think of is that I recently installed the Knock app to use my iPhone to unlock my Mac. Since that uses Bluetooth Low Energy, could that be causing some kind of issue? I suspect not, again, since I'm using a 5GHz wifi network.

Thanks!
 
Last edited:
Solved...I think

OK, so last night, I tried another test: leave everything plugged in, but move the MBA itself as a far away from the monitor, keyboard, etc and close to the router (~5ft away). I left the computer asleep and then woke it up -- slow internet. Therefore, I basically ruled out any sort of interference.

The only thing difference with my computer setup other than moving physical locations was that I installed Knock, and that was somehow conflicting with wireless networking. Perhaps toggling the Mac onto battery power then back to AC powered down bluetooth or something as a normal battery-saving thing. (?)

Nevertheless, I uninstalled Knock, repaired permissions and did a full shutdown and restart. (Granted it could had been a simple permission and restart that would fix it and not caused by Knock at all -- but Knock is not really a a necessary app for me regardless.) This morning, I woke my MBA, while all plugged in and setup on my new desk, and all is fine.

Anyway, thanks for all the help everyone! Hopefully my issue is solved!
 
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