I've been happily using Powermid IR extenders to make my modulated video easier to use throughout the house. But, sometimes I have noticed that the regular IR remote in the mail video room loses range (as if the batteries are dying, but even with new batteries), or that the distant locations don't seem to be effectively transmitting the signal.

Well, I diagnosed the problem, but I still can't figure out what's going on. It seems that my Macbook Pro laptop is somehow generating RF that is being picked up by the Powermid RF Receiver/IR blaster, producing a constant stream of junk IR signals that is interfering with my normal AV remote controls.

I tried turning off the Bluetooth and Airport networking on the laptop, to no avail. When the laptop is powered up, the Powermid goes nuts. When it shuts down, the Powermid is fine.

I should note that none of the other computers in the house do this (Dell desktop, Dell laptop, home-built desktop).

I'm at a loss -- does anybody have ideas for why this would happen, or what I can do about it?

I got the answer in the Macbook support forums, but thought I'd mention it here. The response I got was

If I recall correctly Powermid is a 900MHz RF system. AP and BT are 2400MHz and unlikely to interfere. The more likely scenario is RFI on an overtone harmonic of the system bus. The lap top may meet FCC class B specifications and still radiate unwanted RFI.

Reorienting the antenna or using the laptop in a remote or shielded area are about all you can do.

By changing the antenna from vertical to horizontal, the problem goes away and the powermid still receives fine from the other end of my house.

Amusingly, if I then turn the Laptop on its end, the problem reappears. I also found that the interference seems to be coming out of the back of the Macbook. If I turn the laptop 90 degrees from its usual orientation on the desk, the interference pretty much goes away. Turn it 180 degrees and it disappears entirely, even if I place the laptop within a foot of the Powermid receiver. If I leave the laptop in its original orientation but lift it a couple of feet, the interference also goes away.

So, the Macbook Pro seems to be shooting a horizontal beam of 418 Mhz radiation out its backside. That wasn't mentioned in the manual. :D