LOOKS LIKE LOTS of Penguins! The card is a QSL ( I'm a Ham Radio Operator) The term QSL means confirmation of radio contact. Gives call sign of the stations,equipment used, time,frequency,and signal report 1-5 Strength 1-9 quality Example 59 would be a great signal. I'm also US NAVY vet. Antartic service was very difficult to get, you could not have any dental fillings (air temps can go to -100 f) Nice card. Also very dificult contact for Ham radio operators , because of radio wave propagation around the polar regions (northern lights-Aurora borialsi)KC4USN is call for Antartica research station. These cards are only sold when a Ham operator dies (he is then refered to as a "Silent Key") 73 K4YYY
"Home brew rhombic" is not a handle; it's the shape of antenna used, probably made out of the ubiquitous scrap metal that seems to proliferate in polar habitats.
BTW, I have bought lots of QSLs from living breathing hams. Move down south, the cards get sold and the ham shack dismantled. "Bigger and better" at the other end, but it never seems to happen, too much golf, fishing, and boating to CQ again.