^ Maybe that's it; I have a long commute (2 hours each way) to work through some pretty rural areas. I have never really checked to see what sort of coverage I get (WiFi on the train, so I am always working on my laptop), but I am going to look into that...
As for going into airplane mode while recording, I don't bother. Everything is balanced and, even if I turn my phone off, every other person in the venue will likely be using theirs continuously for the entire show. Plus I never get any calls. I guess I have just been lucky, because I haven't gotten any interference.
I think I might buy one of these just for fun. I usually run omnis on a wide (66 cm) bar and I am thinking I could easily, and pretty inexpensively, run this in the center of that bar. Almost no extra gear: some gaff tape, the mic, a cable.