Pete Bertini wrote:
As an academic exercise, for example using a tapered
line to match an OCD with a known FP impedance of 200 ohms
down to a 1:1 balun at the 50 ohm coax line transition point.
What is the recommended minimum length of cable needed to
perform a four to one characteristic impedance change in the
open wire for relating to the wavelength?


What's the VSWR and frequency spec?

50 ohm balanced pair might be hard to come by.. the usual 276*log10(D/d)
equation is only valid when Dd. (D = spacing, d = diameter) and just
ballparking 50 ohms means that the spacing between the wires is about
10% more than the diameter (D/d 1.1). 200 ohms is more like D/d = 3