Resolved Strange behavior: Connecting external display affects the wireless connectivity

Discussion in 'MacBook Pro' started by dikafe, Oct 14, 2012.

  1. dikafe, Oct 14, 2012
    Last edited by a moderator: Oct 14, 2012

    dikafe macrumors newbie

    Joined:
    Oct 14, 2012
    #1
    Hello!

    When plugging an external display in the mini display port, the internet speed decreases significantly. Not such of a big issue, but strange and unexpected behaviors are always annoying.

    I'm explaining my problem in details, but first let me apologize for bad English and/or lack of accurate technical terminology. Well, I have a MacBook Pro, connected via Airport to the router and by taking internet bandwidth tests (using the Speedtest.net), I've noticed large variations in speed performance (i.e. from around 20Mbps down to less than 1Mbps DL speed). Apart of the tests, the bad correspondence is obvious by using internet and further the WLAN (I have also attached an external HDD on the router). I live here for a short time, but I took the tests at different times during the day and for several days, since I'm unaware of how the ISP traffic might influence the speed and performance. I have restarted the router many times, which is located in the same room with the computer and functions under the 802.11g protocol (no firmware update have been found).

    I most of the times have plugged different stuff in the computer, like the external monitor, wireless keyboard, mouse, but recently i unplugged everything and tried a speed test next to the router. The speed reached the peak, so I moved the computer back to my desk, and the test scored similarly high-speed results. So in this case, I secured that the distance was not playing important role, as expected i guess, within a small room at a distance of 3-4 meters from the however low-class router. When starting to plug in the peripherals again, I noticed that, when connecting the external display and only then, the speed falls significantly (to around 1Mbps). Removing it, performing the speed test (speedtest.net again) and the results go high again (to around 15Mpbs). So, there they stop my observations.

    One of my assumptions is that power used to feed the signal for the external monitor affects the power that the wifi antenna is using (like as the computer was moved far from the router. However, the connectivity indicator still displays excellent communication with the router.) Is it this a silly idea? Or could it be any frequencies interference? I don't hope to a solution so much (due to the bizarreness of the case), but I would be glad for your opinions, ideas, suggestions, even reproduction of the issue. By the little I've searched, I haven't found a related thread, but I'd be happy, in case someone can lead me there. Finally, i'm sorry for the text's length, but I wanted to describe the situation as precisely as possibly I can think of.

    Cheers!
     
  2. stridemat Moderator

    stridemat

    Staff Member

    Joined:
    Apr 2, 2008
    Location:
    UK
    #2
    Are you able to connect to the router with a cable and then re-run your tests (with / without screen). Might help pinpoint the cause of the problem.
     
  3. dikafe thread starter macrumors newbie

    Joined:
    Oct 14, 2012
    #3
    Thank you Stridemat for your direct response! It took my some time to stretch cables and so forth, but as I mentioned the desk is not that far:). Anyway, I believe you have something on mind, because I took the tests again, and with either the external monitor in or out the results showed high scores (even higher of course than the wireless connection). I actually repeated a wireless test just now (monitor plugged) and the result is disappointing at 3Mbps against around 30 (on wired connection, DL speed always).
     
  4. stridemat Moderator

    stridemat

    Staff Member

    Joined:
    Apr 2, 2008
    Location:
    UK
    #4
    So it seems you have a problem with your WiFI then and not your Mac or the router.

    The only thing I can think about doing is to change the broadcast channel to a different one. Maybe the monitor is interfering with it. Worth a try :)
     
  5. dikafe thread starter macrumors newbie

    Joined:
    Oct 14, 2012
    #5

    Thanks again! I recently changed it in order to avoid interference, when the router was further in the apartment at that time and the signal very poor. So I'll try your recommendation and let us know.:)
     
  6. dikafe thread starter macrumors newbie

    Joined:
    Oct 14, 2012
    #6
    Such a pleasure! After playing around with different channels, I found one which worked pretty well!! Funny think: Even after more than one test, the results were always some better WITH(!) the screen, instead of without...:) Anyway, I would never expect that a wired device would interfere with the wireless network!...

    A note here (probably for newbies like myself, unless a local case): When switched to channel #13, the router would not being seen by the airport. Connecting it with cable I changed the channel to another that worked before. I guess the specialists out there know the reason.

    So, stridemat, you rule!

    (I'm trying to see how I declare the issue 'Solved'
     
  7. stridemat Moderator

    stridemat

    Staff Member

    Joined:
    Apr 2, 2008
    Location:
    UK
    #7
    Done it for you ;)

    For future reference if you edit your original post, click go advanced, the you can add a prefix.

    Glad I could help.
     

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