"Flying Pig" wrote in message
...
..

That said, there's gotta be a reason the military uses milspec stuff, at
well over double the cost, perhaps included being the double braided
jacket making RF migration/insertion pretty much impossible...

Ideas about that?


Double braid still gives only 95% shielding. The LMR400 is 100% shielded
because of the solid foil in the outer jacket.

As far as the "milspec" hype:

http://en.wikipedia.org/wiki/Coaxial_cable

"A series of standard types of coaxial cable were specified for military
uses, in the form "RG-#" or "RG-#/U". They date from WW II and were listed
in MIL-HDBK-216 published in 1962. These designations are now obsolete. The
RG designation stands for Radio Guide, the U designation stands for
Universal. The current military standard is MIL-SPEC MIL-C-17. MIL-C-17
numbers, such as "M17/75-RG214," are given for military cables and
manufacturer's catalog numbers for civilian applications. However, the
RG-series designations were so common for generations that they are still
used, although critical users should be aware that since the handbook is
withdrawn there is no standard to guarantee the electrical and physical
characteristics of a cable described as "RG-# type". The RG designators are
mostly used to identify compatible connectors that fit the inner conductor,
dielectric, and jacket dimensions of the old RG-series cables."

If someone starts quoting "milspec" you can bet they haven't a clue what
"milspec" even means. A fair amount of "milspec" electronics can't endure
automotive temperature ranges, oil field conditions or other industrial
settings. Buy what suits your application best. The center conductor in the
PTFE filled RG-214 is prone to migration because teflon is easily displaced.
There are minimal bend radius for the cable.

If you have any leakage in your cable (such as RG214 does with only 95%
shield) and you place it in a conductive solution (such as salt water) you
are in effect adding a third coaxial conductor to the transmission line.
This will change the impedance of the line, increase signal loss and radiate
radio energy.

On Sun, 13 Dec 2009 16:16:34 -0700, "Stanley Tobasco"
wrote:




Double braid still gives only 95% shielding. The LMR400 is 100% shielded
because of the solid foil in the outer jacket.

Aluminum foil as I recall - good stuff indoors.