It's a 300 ohm to 75 ohm adapter. Just like a older TV would use. Screws on one end and a female F connector on the other. Link is below.
http://www.amazon.com/75-to-300-Ohm-Matching-Transformer/dp/B000E9U9A8/ref=sr_1_3?ie=UTF8&s=electronics&qid=1241407945&sr=1-3
http://www.amazon.com/75-to-300-Ohm-Matching-Transformer/dp/B000E9U9A8/ref=sr_1_3?ie=UTF8&s=electronics&qid=1241407945&sr=1-3