I wouldn't use silicon compound. Just wrap with tape. If you want to
keep moisture out, just put a bit of silicon grease in the connector. If
you ever have to take that cable off in the future to check something, and
believe me you will, coax seal or the like is a real pain. I tried it for
a bit when I was doing commercial satellite installs as well as commercial
two-way, and soon gave up on it. Just my two cents.
73s
Butch Bussen
wa0vjr