For duplex systems the double shield of aluminum foil and copper braid is the problem. RG214 double shield is 2 layers of copper braid and is ok.
BB
+1 On the Braid Shied Mismatch.....
For the mobile repeaters. (i've done a bunch using superflex 3/8 and even 1/2 with that last 1-3' transition made w// RG214.)
For the most part, if the "end-user" person/agency is educated on how to properly handle the "cable", it usually works out well. (be careful with bend radius issues/kinking and crushing etc.) I even built one using a 100'+ length of 1/2" fsj4 for a Fire Dept using a rather tiny mobile repeater for fireground operations using an inexpensive 3db gain omni 2' fiberglass "stick" that we designed a small magnetic physical mount for to allow them to "stick it" onto a steel plate on an aerial ladder. the "transition" to very flexible cable was a 10' section of RG214 pre-fastened to the antenna and mechanically secured to the mounting bracket/magnet kit with a drip loop and a few pre-attached velcro straps to coil it all back up again. Installed a male "N" on the end and fastened a plastic/rubber style connection covering enclosure (hard to describe - but is "clipped" around the connection between the long length of superflex and the antenna rg214 lead. and it "locks" in place and then velcro straps secure it from opening . (offers a bit of protection from water infiltration) - and left additional lengths (all marked by colored heat shrink tubing near connectorized ends and every 2' or so on the entire length. helpful for identifying cabling when multiple runs are laid out in place during a hectic setup scenario as well as identifying the length of the cable when looking through a plastic bin or milk crate for a particular length. (blue=100' / purple=50' and yellow for 25' assemblies) Also, make sure to leave a "kit" of spare connectors/adapters/"oddball" parts and tools etc.)
Oops -- forgot to include: Remember about grounding/bonding issues. (all depends on antenna location / power sources / heights involved / etc.) but definitely an issue.
For your fixed sites: using 1/2" "Hardline" (foam core dielectric & FAIRLY flexible) FSJ4-50 style for the major portion of the run and switch out to a short RG-214 jumper (for the flex factor) is the way to go. Make sure to use SILVER or SILVER PLATED connectors and not the crappy Nickle Plated $.23cent variety.
If you are intimidated by the termination process of the Andrew/Commscope "heliax" portion of the project, you can readily find pre-terminated (factory) common lengths of the cable on FleaBay. (25/35/50/75 are the most common factory packaged assemblies) - The cost is not very much higher than the 3/8" (FSJ2) and, will really hold up well. Just be careful when buying -- Ensure you are not buying the 7/16"DIN connectorized cables mostly used for the cell phone industry as "jumpers" to equipment.
Just a tip-->
If assembling our own assy: You might wanna give the older connectors a shot - the "Solder Type". I've had better luck with long-term lifespan when using these vs. the "clickstop" etc. style connectors. It's considerably more work / tougher on a tower or roof on a frigid day / takes more time / connectors are brass in composition and color but I always use mil-spec dielectric and also corrosion inhibiting products on all connections anyway and always use multiple mil-spec double walled adhesive style heat shrink tubing over the area where the fitting attaches to the "cable" mostly as a strain relief, then wrap the finished connection (to "jumper" or antenna or anything else) with "silicone self-fusing tape" to keep the whole connection from turning into a gooey mess with adhesive etc from conventional tape or butyl mastic etc. -- but then I usually finish up by covering the self-fusing "tape" with several layers of scotch 33+ or 88 electrical tape and, if a really harsh environment, a coating of liquid scotchkote "liquid tape". If you ever have to service the connection (or even a grounding kit connection for shield ground kit) down the road, just carefully slice the whole thing open with a sharp utility knife or razor blade and ... violla-- a clean/dry connection to work with)
I've seen LMR-400 installs that work just fine / and have seen some that are true nightmares -- especially with "static" and "crackling" noises and intermittent problems. So, save yourself the aggravation and just do it the right way the first time.. It's fine for long portable runs / fixed base units / remote receiver sites / etc.. but for a fully duplex system (repeater) installation, stick with hardline / superflex / rg-214 / etc. - and remember grounding/bonding requirements and surge/lightning protection. Polyphaser is your friend. LOL
Good luck w/ the project. !
