Setting up a WiFi network from iMac... works on "old" iMac, not "new"

Question

Hello,
I hope I'm not crazy, or even worse, stupid.
I an running two iMacs in my home office. Old one= 21" 2 Ghz PowerPC G5, purchased summer 2005 and still running like a champ.  New one=27" 2.7 Ghz Intel i5. Purchased the new one July 2011. I have a cable modem plugged into the ethernet port on the old iMac. I've been accessing internet on new iMac with wifi and the internet sharing network I set up on old one. I also use wifi on my ipad and laptop. I have never had even a single dropped wifi connection on any of these devices.
I pretty much expected the same kind of result and performance when I reset the cable modem and plugged it into the new imac and took similiar steps to set up  internet sharing/wifi network on new iMac. This has not been the case.
What's happening is:
The cable modem plugged to new iMac is working fine; verified with ISP. I set up wifi network on new iMac and turn on internet sharing. I locate my network name on ipad, laptop, even the old iMac, and I see the name in the list, so I figure so far so good. The signal icon appears in menu bar as usual. I open a web site to verify it's working. And it's working...for about 20 seconds. Then I get alert messages that there is no internet connection.
After creating a bunch of new networks and changing channels, changing type of security, even passwords, I realized I wasn't going to figure this out by myself. I'm not a technical person; Apple spoiled me and I stopped learning how to do anything except plug stuff in 20 years ago.
I started researching online including these discussion boards and answers have ranged from "It's the iMac! It's a hardware problem they never fixed! The aluminum case gets too hot!" to, "there's no airport card and you have to buy an external router."  I gave up and called Apple, thinking surely they'd be able to give me a straight answer. Ha ha. Nope.
Of course the bottom line is I could buy applecare (haven't yet...haven't used the computer hardly and I'm still under warranty), I could buy telephone tech support, or I can take the machine to the geniuses.
I keep thinking this can't be that complicated. When I buy a new iMac--this is my 4th one--I expect things will get easier, not this complicated mess.
Oh, last I want to include I just reversed everything back to the way it was. My old iMac is connected to the cable modem and the old iMac is back to being my wifi network, sharing internet with the new imac, my ipad and laptop. Easy as pie.
I'm making an appointment with the geniuseses but hoping it's just something I'm too dumb to realize I'm doing wrong.
Thank you in advance for your patience; any help is much appreciated!

Answer 1

SuznK66 wrote:
It never occurred to me that the wireless network/internet sharing thing wouldn't work just as well if not better on a brand new machine with the improved technologies I pretty much expect. Metal could be interfering with the signal? The machine is aluminum!! I'm no engineer but that seems kind of...flawed.  I just don't understand.
I think the WiFi antenna is near an edge of the computer to avoid being encased in metal. It should work like t did in your old computer, but as I said, the use of a Mac to share an internet signal is much less common than use of a router so even if the newer computers have a non-optimal design, it might not get widely noticed in forums like these.
Sounds like AppleCare is what you want, so I'd get it and then have them check that your Mac is transmitting thru the wireless card/antenna as strongly as it should be. The antenna clearly works as you can RECEIVE a signal, but the transmitter uses different circuitry than the receiver. By the way, I think AppleCare is a good thing to get for iMacs and for laptops as they are very compact and tend to be more prone to thermal problems than other desktop computers.
I have no idea about routers aside from, of course, the apple air port one that the phone tech support guy mentioned. Are there others that are less money and just as good? I don't feel like rewarding apple for selling me a product that doesn't do what the earlier geration machines did without a problem. Seems like they shouldn't make another $200 because of their flaw. My old iMac's wifi signal was strong enough for a 3500 square foot house, 2 laptops and an iphone.
Would getting an external router definitely solve my problem? Which one would you recommend if I go that route?
I also did not understand why the Apple routers (Airport) were so much more expensive than other brands. So I purchased a linksys n router some years ago and it has worked quite well. They are very easy to configure through an ordinary web browser (some Mac folks prefer the Airport utilities that are used to configure the Airport routers, but I find the web browser interface very easy to use for the non-Apple routers), and they are in very widespread use (linksys isn't the only brand that is good for this, there are others, but I've had good experience with both Belkin and Linksys). You can get very high performing n routers from Belkin and Linksys for under $100. I'd get a router that has dual band (2.4 GHz and 5 GHz), and I think most include standard features like MAC filtering (a security measure), WPA2 security, and I thiink offering Gigabit ethernet ports would be good also in case you connect something to it like a hard drive server or a printer or want a fast local network sometime in the future.
I think the router will solve your problem and do a better job of wirelessly distributing your internet signal, but if the problem is due to a faulty wireless card (that receives fine but doesn't transmit properly) in the new iMac, I'd want to get that fixed under warranty (or AppleCare) now rather than later.
One more thing: if your wireless card in the new iMac is working properly but the physical layout is such that the internet sharing isn't working well, you OUGHT to be able to eventually get it to work by moving the other devices you are sharing with around to different locations, as eventually one should end up in a spot that works. If nothing can receive the shared internet from the new iMac, even when 3 feet away, then something might well be wrong with the new iMac's transmitter.