About 3 years ago, having bought my house and living here for a couple of years and figuring that I wasn't going anywhere for a while I decided to set up my first semi-permanent antenna (are any antennas actually "permanent?") Up until this point, I had dealt with water intrusion and other environmental issues by simply bringing the antenna and coax inside when not in use... so, looking to waterproof my connections I turned to what I believed to be the standard in coax waterproofing - coax seal.
I won't even dignify it by posting a link, but everyone knows what it is - it looks like something that was dug out of a sewer lift station... and it WILL cause you problems one day - not the day you put it on, but the week, month or year down the road where you have to take the shit off to undo the connection. DO NOT USE THIS GARBAGE.
I actually discovered that it sucked about a week after using it when I went to undo one of my connections - and despite my best efforts to remove it at the time, the reasons why I hate it linger to this day. My preferred product now:
silicone tape - about the same cost of coax crap, available at a home depot near you. Also sold at parts stores (for a little bit more.) Goes on and comes off easily, far more durable and sucks 100% less. For an extra tight seal - before using the silicone tape, lightly coat the coax on both sides of the splice with a little clear silicone RTV. This will make sure the coax seal "sticks" to the cable and you get a 100% waterproof assembly.