Ralph Mowery wrote:

Roy what kind of coax do you recommend along the same type ? I soon plan on
putting up several beams, tribander for the low bands, 6 meter, 2 meter and
a 432 antenna. Should be running about 125 feet or so. While I know
hardline would be best for the VHF , I don't want to (can't spend the money,
easy to install for the rotator) so I want to stay with one of the
9913/lmr400 types. I have had a piece of 9913 up for about 10 years and it
seems to be ok, no water I can tell, I still would like to go with a solid
foam type instead of the hollow core .

Just looking at the specks and advertising can sometimes be deceiving.

Sorry, I'm not the best person to ask. A lot of the other folks here
have a lot more experience than I do with applications like yours.
Ruggedness and other physical properties can easily be more important
than the technical specifications of a cable under idealized conditions,
so I'd listen to people who have used cable for an extended period of
time in similar circumstances to yours.

As far as loss goes, you're bump up against the laws of physics. Below a
few GHz, dielectric loss in common coaxial cables is negligible. The
shield has much larger surface area than the center conductor, so the
loss ends up being dictated mainly by the diameter of the center
conductor -- the larger it is for a given cable Z0, the lower the loss.
Assuming a fixed Z0, the only ways you can make the center conductor
larger are to increase the cable outer diameter, or reduce the effective
dielectric constant of the insulation between center conductor and
shield. The effective dielectric constant is reduced by using foamed
dielectric coax, or even more by using mainly air dielectric, with a
minimal amount of insulation for physical support. Consequently, for a
given Z0 and outer diameter, and otherwise similar construction, foamed
dielectric cable has less loss than solid dielectric cable, because its
center conductor is larger. Mostly-air dielectric cable has less loss
yet for the same reason. (In the microwave region, dielectric loss
becomes significant, so there's a further loss reduction when the
dielectric density is reduced.)

A stranded center conductor or braided shield increase the loss
somewhat. It's difficult to find definitive data on just how much,
probably because of the number of variables involved, like shield weave
tightness and frequency. But the amount of increased loss can be quite
significant, judging by the actual loss of typical coax vs. the loss
predicted by the assumption of a solid center conductor and perfect
shield. Ian, G3SEK just posted a possible explanation of an additional
loss mechanism for aluminum-foil shielded cable like BuryFlex -- tearing
of the foil shield due to bending too sharply.

But I think amateurs often get too hung up on small amounts of cable
loss. It's admittedly sometimes very important, but not in most cases.
Cost, convenience, ease of use, connector type, and physical ruggedness
might well be much more important criteria. And again, there are a lot
of folks here who have a lot more relevant experience than I do, so you
should listen carefully to their advice.

I do fully agree with your last statement.

Roy Lewallen, W7EL