LMR cables, or any with braid-over-foil, will expand and contract if used outdoors (or in other non-controlled environments), which tends to occur in repeater situations. After a while, this slight mechanical shifting will cause problems, including noise, as the braid rubs over the foil. Dis-similar metals then act as rectifiers (point-contact) as corrosion creeps in. Same thing can happen if the coax is allowed to flex in the wind.
Sharp bending, or repeated bending, will also break the foil and/or mylar wrapping (i.e. inner shield), thus reducing the effectiveness of the foil. The mylar will stretch a little bit, the foil usually fractures. I had two LMR400 jumper cables that have become totally useless due to repeated bending in a 2ft radius arc. I'm pretty sure that this topic has been covered in a couple of articles on www.repeater-builder.com, but perhaps it needs some more definitive statements. Bob M. ====== --- skipp025 <[EMAIL PROTECTED]> wrote: > Depends really.... > > 9913 is a good cable to use if you run modest > lengths, the cable > doesn't have to move a lot and you don't run really > high power. > > Here's the dope... > > The coax is most often a very cost effective choice. > The loss for modest > length runs is not bad. > > You should pay serious attention to the coax > material and mechanical > construction issues for your specific application. > The center > conductor is often mounted in foam or a hybrid air > foam type layout, > which has a potential to become problematic. > > It is possible the center conductor can migrate out > of alignment with > sharp radius bends and heated center dilectric > problems. Because of > these two issues I'm not much of a fan about using > any foam center > coax. There's also a crush problem I'm not going to > address in this > post... > > But I have friends who run 9913 with great results. > > My coax choice before 9913 would be RG-214 mil spec. > > > Stay away from LMR dissimilar metal type coax cables > in/for > duplex (repeater) operation... > > cheers, > skipp > > > > "Howard Z." <[EMAIL PROTECTED]> wrote: > > I have read that one should use dual-shielded > cables. > > Which cables are these? > > Is Belden 9913F7 a good choice? > > Here is its description: > http://www.therfc.com/9913f.htm ____________________________________________________________________________________ Be a better Globetrotter. Get better travel answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545469
