Place your wireless base station close to your computer assuming that is the principal wireless device you have.
The most likely cause is network interference from your neighbours’ Wifi setups if you are using the same band and channel. Here’s a timely article for you from Macworld:
If you hold down the Option key on the keyboard, and select the Wifi icon in the menu bar, you’ll see the band and channels you and everyone else in your neighbourhood is using. Depending on your devices and your Wifi base station, you may be able to run on a 5 GHz band and not receive interference from your neighbours if they are all using the 2.4 GHZ band. This will give you the fastest throughput as well but is weakened considerably if your wireless signal travels through many walls. If the 5 GHz performance isn’t good, then use the 2.4 GHz band but select a channel that isn’t crowded. The only channels that do not overlap in the 2.4 GHz band are 1, 6, and 11. If no one else uses channel 1, then 1 will give you the best performance. You make these selections using the Airport Utility and the option to configure the Airport manually, assuming you have an Airport Extreme or Airport Express base station.
Currently Being ModeratedMay 23, 2011 11:31 AM (in response to Rick Lang)
Thanks, but I have no problems with the wireless network. My MacbookPro, iPhone works perfectly with my wireless network and I live in my house without the neighbors. But the Internet to a new iMac freezes sometimes (especially after sleep) and I have to reboot the iMac. My iMac has been updated.
From a terminal, "sudo dmesg" will show you the kernel ring buffer. You may see some interesting lines in there regarding the wifi.
Have you tried disabling the wifi and re-enabling it? There are multiple things to diagnose -- you may a have station -> AP association but are somehow failing to obtain / renew a DHCP lease.. or maybe the wifi module does not recover from sleep gracefully for some reason.
The contents of "sudo dmesg" might shed some light, though.
Good if you can provide more information. Are you using an Apple Airport Extreme/Express base station or another router? If it often fails after waking up from sleep, that may be a good indicator of what is wrong. If this is a new iMac you should call Apple Technical Support for your free support and get them to document you are having a problem in the event you have a defective or loose Airport card in the iMac. Can you take it to an Apple Retail Store?
I have the same problem. Disabling airport and re-enabling it on the iMac works. I have lots of other devices using the same wireless network without any problems. It's only the brand new iMac that misbehaves.
Currently Being ModeratedMay 30, 2011 12:44 PM (in response to Bo Boivie)
You can add me to the mix too. MBP, Apple TV, PS3 and MB all use the network through my Apple Basestation and all are fine. However, the week old iMac is sluggish at best.
Checked the channels and I am on Channel 1 using 2.4GHZ and everyone around is on other channels
Sorry to say that my brand new 21.5" iMac had the same wifi problems. Took it back to the store and got my money back after quoting Sale of Goods Act.
As Macs are supposed to 'just work' I think it's unacceptable that so many new iMacs costing a minimum of almost £1000 clearly DO NOT WORK.
My faith in Apple is severely dented especially after similar problems with 2 iPads and an aerial problem with iPhone4.
Get it sorted Mr Jobs! Quality control is appalling.
I feel like every single time I buy a new Mac, some "part" is defective. The last issue was with my MacBook, which needed to have the motherboard replaced (that took a couple of weeks to take care of, and I was not amused). I would also highly suggest not bothering with iPods! My experiences with the two I own have been awful. They break so easily after a few uses, and for no reason at all.
I no longer live close enough to the Apple Store to just take a cab (I can't afford a car these days, what with spending my savings on this new iMac!) to return my new iMac 21.5"--although the other two laptops and smartphone in the house work fine with the WiFi here, of course the new iMac does not. I am extremely frustrated with my recent Mac purchases. Someone needs to test these products before they are sold. They cost an arm and a leg for goodness sake!
If someone has a WiFi fix for the new iMac that does not require me to pay someone $120 to drive me to and from the Apple Store, I would really appreciate it!
Currently Being ModeratedJun 16, 2011 1:59 PM (in response to biscuitravioli)
I want to amend my above statement (you can delete it!) because I spoke to AppleCare today and the folks were very nice. I'm not sure my problem is solved (too early to tell) but I was very hot and bothered when I wrote that post. (I am, however, sticking to my story that my iPods have not been nice to me)
I also have the wifi problem with my new iMac. It connects when the computer turns on, but seems to disconnect every few minutes (randomly, maybe a few, maybe an hour). There are plenty of neighbors with wifi networks, but I've done my best to pick an uncrowded channel and the router is about 3 meters from my iMac anyway (in the next room). The other computers / devices in the house don't have this problem. I disable and re-enable AirPort to re-connect to the internet. Very annoying. Sometimes the wifi router needs to be reset, but I think it's only like once a week or 2 weeks that my iPhone can't see the internet either. It's very frequent with the new iMac.
So, what am I looking for in the sudo dmsg log? I can see this:
AirPort: Link Down on en1. Reason 8 (Disassociated because station leaving).
vmnet: bridge-en1: interface en is going DOWN
But what does that mean? Is that just when I turned the AirPort off/on? What are the other diagnostic tools / commands to run? What system logs might hold clues? Or is this really most likely a faulty wifi card?
Hey guys, I am new in the Mac World and I have bought an Imac a week ago, based on my good experience with Ipad 2. I am having the same problem with the wifi only with the new Imac (21'5 ") and not my Ipad. Do you think it is a problem with quality control in some machines ?
Currently Being ModeratedAug 13, 2011 10:01 AM (in response to supekudx)
From what I've heard Apple has been contacting some people with Wifi problems so they can understand them and fix them in a Lion 10.7.1 update which should come out soon.
If you can easily reproduce the wifi problem, then you can turn on AirPort logging. These are the commands a guy from Apple gave me to use:
sudo /usr/libexec/airportd debug +alluserland +alldriver +allvendor
sudo /usr/libexec/airportd debug +LogFile
sudo /usr/libexec/airportd logger
Note that you have to enter those commands in Terminal every time you restart your computer. That will save logs to /var/log/wifi.log, so if the problem reoccurs then you can note the time (hour - min - sec if possible) and give that file to Apple. (The only way I know to give it to them, however, is through bugreport.apple.com which has a horribly out-dated interface, so good luck there. Maybe you can talk to a genius at the Apple store?)
Hopefully the forthcoming 10.7.1 fixing most of the wifi isues, but if it doesn't fix yours then you'll have to do this logging to let Apple see what the problem is.
p.s. My problem is _mostly_ fixed by switching to a different channel. Apparently a neighbor is using some kind of dual-band setup that my iMac was not properly recognizing so the neighbor clobbered the channel I was using and my iMac didn't realize it. Switching to a different channel as far from that one as I could solved the problem. Now I just see an occasional drop of wifi when I wake from sleep, but I think that's a more common and better-understood problem that should be fixed (fingers crossed) in 10.7.1