Here is a typical matching transformer ,
http://www.radioshack.com , type 2062049 in the search box , it matches the 75 ohm coax to the 300 ohm connection of the antenna. Put silicon grease - not sealer - in the boot. Fill the boot with silicon grease and slide it up snug the matching transformer. Do not put silicon grease in the connector that is on the end of the coax. The best coax for the out doors to use is , RG-6U coax , is also called RG-6 coax. The connectors on the ends of the coax will be the compression type connectors. Not the crimp on connectors. The compression type connectors keep water out.