Any coax with PL259 connectors (I use RG8) and a PL259-BNC adapter to plug into the back of the radio. Works good on most everything but 800mhz digital, which isn't an issue for you, works ok on 800 analog. It's a quite good antenna for the price.
For the BCT15X you can use about 25-50 feet of coax with very little loss. The connection on the back of the radio is BNC Female so you will need a BNC male to fit the radio. If you use a cable with PL-259 connectors you can use a SO-239/PL-259 to BNC male pictured below: