Airport receiver
 

Can a computer's wireless receiver or antenna get weak? My MacBook used to get 5 bars of signal strength in my den (80 feet from the router). Now it gets two. I can set my friend's MacBook right next to mine and it gets five bars where mine gets two. If I carry the computer right up to the router I can get five bars again, but it begins to drop if I get 6 feet away. Any idea what's happening?

Possible interference... try forcing your channel selection in your wireless router/AP to either channel 1 or 11...

Unlikely your computer.

It is possible the transistor first encountered by the radio signal as it comes down the antenna and onto the receiver board is faulty. This transistor is commonly referred to as the First RF (us radio guys like to keep it simple). I've seen this on occasion in two way radios but not in a long time.

Has your range also decreased?

Not sure I understand the question. The farther I get from the transmitter, the weaker the signal. At 80 feet the signal used to be adequate, now it isn't. I have to get within 5 feet of the transmitter to get a strong signal. Another, similar computer still gets a strong signal at 80 feet.
I'm going to change the transmitter channel tonight to see if that helps.

The answer is YES it can go bad.

I had a first-gen intel MacBook (2007?) and experienced the exact same problem at home. I even bought a new airport wifi transmitter hoping that the one I had was going bad. No change. I wiped the whole computer and started fresh. No change.

New laptop, problem gone. The antenna is around the screen, and I imagine that after thousands of opening-closings, the connection could have gone bad.

Forget it: I was thinking in a way-off least-likely scenario...

This is what is most likely your problem.

I've tried the computer on a number of different networks and come to the conclusion that it's got something to do with Safari. I can run Firefox all day on any wifi, but within a minute of launching Safari the signal drops to 20% no matter what network I'm using. I can't figure out why.

Check your activity monitor when you fire up Safari. Does it show high CPU or network usage after Safari is fired up and sits there for 20 seconds or so, without you doing anything?

There are some known security exploits for Safari that could be present.

I'd also ensure you have the latest software installed via Software Updater.

Depends on the actual notebook whether or not you can get to it, but changing the radio can be cheap and make big improvements.

I changed the G radio in my Dell out to an N radio, and even still using the G AP it almost doubled my actual tested speeds. Once I switched to an N AP it got faster yet. I think it was like $35.