Does anyone have experience with the Ferra underground radio? I understand cavers and miners in Europe have toyed with it. It is supposed to work up to 1200 meters underground in data mode (less in voice mode), and up to 3km in a shaft or tunnel. It's 1810 to 2000 kHz. Would be very handy for cave rescue or spread-out expedition work. Weighs just under 5 lbs (2kg).