Cecil, W5DXP wrote:
"A ham I knpe uses parallel runs of RG 62 as a compromise. That gives
him a characteristic impedance of 186 ohms for his 30 foot underground
section."

Yes. It`s balanced to ground and has twice the characteristic impedance
of a single run of coax. In the case of twin runs of RG 82, that is
twice a value of 93 ohms, or 186 ohms, center conductor to center
conductor.

I recall analog microwave radios which had their baseband signals wired
with twin runs for each direction of transmission like that to obtain a
shielded and balanced baseband system. It must have been good for the
coax business and it made for a quiet radio too.

Best regards, Richard Harrison, KB5WZI