On 09 Mar 2013 10:33:58 GMT, Rob wrote:

Jef wrote:

First look at the center
conductor. The larger the beter as that is where most of the loss is. Solid
wire will have slightly less loss, but if used with a rotator, it can flex
enough to break over the years. Then look at the shield, especially the
braid. It should be around 95% or beter. This is where the next loss is.
Most of the low loss coax has a foil type shield plus 95% or beter braid.
That applies for under 1000 Mhz anyway. Look at the velocity factor. The
low loss will normally be .80 or higher.

Just to point out that the diameter of the centre conductor is fixed by
the impedance of the coax, the outer diameter, and the dielectric
constant of the insulator. So for a cable that will fit in a PL259 or N
type it means that you will only have a very limited choice or inner
diameters that are dependant on the dielectric used, and that dielectric
is likely to have just as significant effect on loss as the diameter of
the inner, more as the frequency goes up. However, lower loss insulators
generally have a lower dielectric constant which also mean a larger
diameter inner, for a fixed outer diameter.

Jeff

Also, it needs to be pointed out that the original poster asked about
differences in make of coax, while the discussion now focuses mainly
on type of coax.

Of course, that is a different topic. There are differences between
types of coax (solid center vs stranded, solid dielectrum vs foam
or air or helix or bamboo etc, foil shield vs braid or both), but
what the OP asked is if an LMR-400 from one manufacturer is equal
to an LMR-400 from another manufacturer.

In that case, the diameters, insulation types, braid types etc should
be the same and it is only thw manufacturing quality that would be
different.

However, always check. There always are manufacturers that try to
get away with using less copper in the braid, for example. Copper
is expensive these days.

Thanks to you, Ralph, and Jeff for your kind responses and some great
information - just what I needed. I've a little more research to do, but I got
the answers I was looking for, and more. I really appreciate it. This is a great
group.

73, Bob KB2ZGN