The Airport on my MacBook Pro seems to search for networks every 15-20 seconds or so - (at least, if I move the cursor over the icon in the menu bar, it shows that it searches often) . When I was trying to stream music, that seemed to be one reason for so many dropouts. It also seems to effect Skype and iChat quality. The other Macs do not seem to search anywhere near as frequently as the Pro (in fact, as I write the Pro and MacBook are side by side and the MacBook has not once started searching for networks). We have many networks in our neighborhood, but the home network I use is on the top of the list of preferred networks. What is going on with the Pro and how can I get it to stop searching so frequently?

Does the MBP scan as frequently as you think at any location you try it? It seems to me that the issue may indicate either a local signal strength or an MBP reception problem. The latter may be hardware or settings related.

How can you tell how often AirPort scans?

The only time I'm aware that it's scanning is when I click on my menu bar icon, and it invariably scans when I do that.

Sorry for late reply, guys. Was profiting from last days of summer to head up Mt. St Helens....

As experiment I have all three computers side by side, 2' away from Extreme. Clicked on Airport icons in menu bar and all three drop down menus are visible. All three cmputers are logged into same network. MacBook Pro is "Looking for network" every second. MacBook and PowerBook G4 have not searched once.

Any thoughts? Mind you, the Pro is the laptop that had a large mug of tea poured into it 3 years ago, and has since then always been funkier.... but not sure why this would affect Airport....

I assume there's a difference in OS versions, that would almost certainly affect it. And perhaps the hardware itself is playing a role in scanning?

Also are you comparing them all while they're connected or not connected?

There is more detailed scan information available in console iirc.

spmcc123,

1.)
PowerBook G4 1GHz PowerPC / Wireless Card Type: AirPort / Wireless Card Firmware Version: 9.5.2

When booted from a Mac OS X 10.4.11 or a 10.5.8 volume, and when clicking the AirPort icon in the menu bar, the only items displayed are:
• AirPort: On
• Turn AirPort Off

The PowerBook G4 never reports "Scanning..." or "Looking for Networks..."

2.)
MacBook Pro 2.4 GHz Intel Core 2 Duo / Card Type: AirPort Extreme / Firmware Version: Broadcom BCM43xx 1.0 (5.10.91.27)

When booted from a Mac OS X 10.5.8 volume, the initial list reads:
• AirPort: Scanning...
and then changes to
• AirPort: On
There are no changes after this.

When booted from a Mac OS X 10.6.4 volume, approximately every six - eight seconds, the list alternates between:
• AirPort: on
• AirPort: Looking for Networks...

Clicking on the AirPort icon invokes the scanning / search for networks. The difference for me seems to be hardware.
[edit to insert]
And operating systems – Leopard and Snow Leopard.

Thanks for the detailed analysis! But the poor layman still wants to know: "what can and should I doooooooooo??" nothing?

Good question!

In the interest of narrowing the solution space to your problem try the time honored, tried and true troubleshooting step of creating a new user account on your Macbook Pro (System Preferences > Accounts and click on the plus (+) sign at the bottom of the list of user accounts) then logging onto the new account connect to the network and then see if the MBP continues the too frequent search for the WiFi network. If it does not continue to search then we have narrowed the solution space to something in your user account. There are lots of ways to go from there so let us know what happens.

If the network hunting continues in the new account, I would go online find the page for my nearest Apple Store and make a Genius Desk appointment and take the MBP in to let the "geniuses" see what they can figure out. There are a lot of good folks here with a lot of knowledge, but there is only so much that can be done without laying hands directly on the hardware. (At this point you may wish you were still under Applecare. )

An off the wall suggestion presents itself to me. I haven't suggested this in a long time, but another thread on these forums reminded me of something that cannot hurt, takes minimal effort and time, and has been known to help in some really surprising situations. Open Disk Utility, select your hard drive and run Permission Repair. It probably won't change a thing, but as I said it cannot hurt anything and there is an outside chance it might help.