I did wonder about that, of course. Most RFID from phones and stuff is very short pulses. I can hear my phone emitting pips if I unlock it while sitting in the house even though my antenna is outdoors, attached to a shed. I'm in a suburban residential area in a small city so there aren't too many other things out here, and I've listened to this band before and never heard something quite like it. It's still possible, of course, that I was hearing some random thing, but it was definitely new to me, whatever it was.