>"This one I haven?t been able to identify is (as closely as I can measure
with a tape measure) 1/8? larger over the dielectric than the 7/8?. "
Stan,
Is it possible you have a roll of 75-ohm cable? When I was employed by
AT&T Broadband, in some instances we used Commscope 1-inch corrugated
coaxial cable with a solid inner and foam dielectric. You could get a rough
idea by applying the simpler formula: Zo=138 × log10(D/d), or better still,
with a cable that long, use a VNA and get a S11 measurement by alternating
between 75 and 50-ohm terminations.
Paul, W9AC
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