I'll be mounting an A99 to my chimney. Bottom of the 99 will be in the 23 to 36 foot range. I'll be using a 10 foot galvanized mast that will be sunk into the mounts about 3 feet. That will leave about 7 feet of mast above the top mounting bracket. For coax I have a 100ft run of LMR 400UF. My question is do I just attach the coax and zip line it to the mast in a straight run down? I see a number of references on the forums to using a choke or balun. Any suggestions?