Forums | MacLife

This looks promising.

http://bounav.free.fr/mods/ae_external_antenna/

How about one more Airport in the close vicinity of the BBQ ?   Or, what's the distance between your 2 airports now ?

Perhaps you should try to take the BBQ's stainless steel case out of the equation (at least temporarily) by attaching its AirPort Express (AE) to a short extension cord to the outside of the BBQ's case. It could be that the signal from your other AE may be attenuated due to other reasons like metalic backing to your house's insulation or by another wireless network in the area which is using the same channel as yours.

If your problem turns out to be interference from another WiFi, try setting your AEs to a specific channel: most WiFi use channel 11 by default (including AirPort), so try using channel 1 or (if that is also occupied) 6. While there is an automatic setting for AirPorts, I've found in my particular situation that choosing a channel substantially helped. Remember that there can be other sources of interference, some temporary like wireless phones that only interfere when being used, so this may not fix the problem permanently.

If the problem is due to something about your house interfering with the signal, then you might try Nefarious' idea of getting a third AE to act as a signal booster to get to the one on the BBQ.

If the BBQ case is the culprit, then your option may be to add an antenna that gets outside the case.

Something just occured to me: how hot does it get inside the box where the AE resides on the BBQ? I presume that this is somehow insulated or separated from the oven part, but if it gets too hot this may cause the AE to malfunction.

From your thorough explanation, my guess is that the source of your interference is something temporary like a 2.4 Ghz-band wireless phone--either yours or a neighbor's, depending on how close the houses are--which is causing the problem. There are other non-obvious problem makers for the 2.4 GHz band. One is a type of light (usually used outdoors) which used microwaves to excite its lighting element, and the microwaves it used were in the 2.4 GHz band (not likely in your situation, just an example of a non-computer usage).

You might let iStumbler run on your iMac and see if it records some burst of traffic/noise in the 2.4 GHz band and see if that coordinates with problems you have with the BBQ unit. As to tracking it down once you determine that it isn't anything on your property...well, good luck.  Short of getting a directional antenna to at least limit the possible directions or wandering around with iStumbler on a portable Mac I'm not sure what to do to further pin down your interference source.