Haven't seen any response to this, James, and am probably not going
to be much help.

I've just used RG58 variants for up to 100' in permanent 
installations around the yard, 10 to15 years in some cases.   One of 
them runs through about 70' of rigid PVC electrical conduit IPEX 
#032907 and is buried.   Mind you, I've heard that although such 
conduit will keep the groundwater away from the coax, water vapor 
will condense inside, leading to a wet interior anyway.   That coax 
still seems to work,so maybe it's dry...or maybe not.
On DXpeditions, I've run over 500' of  RG58 coax to DKaz'es and such, 
and not suffered particularly.
best wishes,
Nick

At 22:26 2019-01-27, James Niven wrote:

I am curious as to what type of coax everyone uses for DKAZ antennas and
also general international shortwave band listening dipoles?
It's time to revamp my antennas and I want to use the right cable that will
last for a while.
I have read that RG-8U is good for long runs of a 100 to 150 feet, and if I
was to bury my coax, which is the best pipe/conduit to use to bring my
cables into the shack?
thanks
James Niven
Austin, Texas