There are plenty of big hardwood trees around here, especially in the valley along the banks of the river. Finding appropriate lumber for the job is not the difficult part; getting it up the side of the mountain, on the other hand, is.

Other Answers:

1. The flare-ups are irregular; some happen close together, some an hour or two apart.
2. Just more screeching, yes.
3. Similar effect to when this was tried by the beach: There's loud screeching when Jet holds the transceiver underwater, and less or no screeching when Martin holds it instead and Jet goes away.
4. No messages or other notifications when the attachment screeches at them, no.
5. Roughly a kilometer.
6. They don't see any signs of recent habitation (that doesn't necessarily mean there aren't any, though).