Hi Paul, buy a tube (or 2!) of electricians' silicone grease 50g tube usually around £4ish. A bit squeezed into the end of co-ax will seal the cable a treat - won't take solder then though, only crimp type. If soldering, apply the grease after, squeeze a good bit into the connectors then assemble, may squeeze out a bit, which is good. You can also buy blind gland covers for outdoor cable, which will puul down over a joint, leave bottom end open for ventilation, a plastic drinks bottle can be used the same, with a hole drilled (slightly smaller than cable OD) in lid, doesn't look so professional though. Heat shrink can also be used for covering joints, any more hints wanted, just ask..........