https://sites.google.com/site/scr269onuscgvessels/ Look at the pix above. Sure looks like LP 21 loop antennas to me. Still researching this topic. Ran into a couple of old Coasties who said that some rescue boats did have marine Band 2-3 MHz AM ADF capabilities, but they were not radio guys and didn't know details. Any info appreciated. 73 AF6IM