Thank you all!

@K1TTT
Yes, that's the technically idea solution, but I am trying to use
common materials that cost perhaps 5x less around here.

@'Doc
You have a point. I wrote RG-6-"type". There's a ton of various cables
types that are sold commercially as "similar" to RG-6. I referred to
the sat-tv cable that everybody uses around here, and you find it in
every electrical supplies shop. This cable is designed for use at
about 2GHz, which is the IF at which signals are sent down from the
LNB to the receiver.
- solid copper center conductor
- foamed PE dielectric
- 100% AL first shield, perhaps .1mm foil
- probably 60% AL second shield, stranded
- insulation 3kV DC test, in practice not a problem (if you don't
crush/melt the foam :-)
- emphatically NOT rated for power, tested and perfect up to 50W QRP
and RX, theoretically could take 1kW if well matched and not overheat
(see specs, do the math) but I never tried and ever will, I'd guess
will take 100W OK. I should do a high-current DC test perhaps.
- pain in the rearend to mate the AL to anything, must be pressure-
only, must be silicon grease coated on penalty or corrosion, but after
all this is how perhaps 300 million sat-TV systems work at 2GHz.
- loss 2dB/100m (m not ft) @ 10MHz, not bad
- ...75 ohm, but I either make my own impedances, or not care, or use
tuners, and 75 is OK for many applications.

@KD7HB
Plastic tape is probably the simplest and best, perhaps without even
wrapping the whole length - at a 30deg. angle spiral wrap I would need
240ft of tape! :-P. Also, tape is much gentler than sttap in terms of
pressure per unit of surface. Dish installers never use nylon straps
outdoors, just several turns of black, weather resistant PVC tape, and
it lasts at least 5-10 years. In my case, the drop is all inside a
flue line, well protected. Maybe I should use a large rope just for
wider surface. I'll do an overload test and see.

But another post around her tells me that perhaps there's a was to
test the line at 2GHz...

Thanks again to all.