The trouble with pre-made boots is they require a specific sized hole in the wall and if the opening is not the right size it won't fit. I have been using the canned foam with one addition, I use some pieces of high density packing material inside the wall, so the foam isn't required to fill the entire wall space, and to keep the stuff from dripping down on the inside while you are shooting the stuff in from the outside (its pretty liquid for a few seconds before it starts to expand into foam). I even stuffed plastic bags around one cable so that if it had to be removed someday the foam would not adhere to it. The can says the stuff is not UV resistant and should be used inside walls or doors but so far the sunlight hasn't "killed" it.
Besides acting as a drip loop, a one or two turn coil of cable outside the building adds inductance for the path of a possible lightning strike and when grounded properly will reduce the amount of energy that finally gets into the building, according to some lightning prevention studies. I've only seen this method used on a few commercial broadcast sites, perhaps because the person installing the cable is trying to keep the length of cable as short as possible to save coax and/or reduce costs or keep feedline loss to a minimum. Its also a trip hazard, what with the 1.5 ft bend radius of some 7/8 coax and for 1/5/8 its a huge loop but that's the way I would do it if I were asked to do a proper job. --- In [email protected], Chris Robinson <kf6...@...> wrote: > > If it is already a completed install , I would use a large crack and gap > filler silicone. I have not used any foam types so I cant say as to how well > they work, but if water is an issue, I would expect foam to act more like a > sponge then a sealer. > > If you can pull a drip loop into it that would be even better. sometimes a > person will leave enough cable to pull the loop into play other times they > cut and pull it short and tight and that sucks. I have made companies go > back and fix the proper way when I did installs in Ca. > > Good luck with it > > Chris > KF6NFW > > On Fri, Aug 14, 2009 at 11:56 AM, wa5luy <wa5...@...> wrote: > > > > > > > > > What is the best way to seal up the gaps around coax cable at the building > > cable entrance port? Our location has a panel with rubber knockouts. Some of > > the gaps are large. > > Unfortunately the original contractor that installed the cables did not > > leave a drip loop and after a heavy rain we get some water in the building. > > Also the gaps are easy access for bugs and mice. > > > > We have considered using Great Stuff foam insulation but are not sure if > > this is the thing to do. Suggestions appreciated. > > > > Wayne WA5LUY > > > > > > >
