For a great tutorial on waterproofing coaxial connectors, check out this post by Paul, AE5JU, over at K9ZW’s blog. I didn’t use Scotch 130C Coax Seal like he does since by the time I discovered its existence I was out of time to acquire it for this project. Next time!
[Update: After the helpful comments I received on this from VE3WDM and others at amateurradio.com, I’ve ordered some coax seal and plan to finish the job as soon as it arrives. What I’ve done here is better than nothing — certainly good enough until I can get the good stuff — but it doesn’t afford long-term protection.]
[Update: When I went to put on the coax seal, I discovered my nice pretty electrical tape already coming apart after less than two weeks! Use coax seal! Another thing I’ve learned about is “Magic Tape,” the self-amalgamating silicone tape you can easily find even at stores like Target and Walgreens. Some hams have told me it works great to put over the coax seal.]
What I did do was wrap the connectors with teflon plumber’s tape, then covered it with black 3M electrical tape. The teflon tape is intended simply to keep adhesive from gumming up the connector. I put several layers of electrical tape down and made sure to wrap the last layer up, i.e. toward the sky, so that the turns are stacked like shingles on a house with their seams pointed downward. Here’s a slideshow: