Coax cable calculation
On Tue, 10 Apr 2018 08:11:37 0700, Jeff Liebermann wrote:
On Tue, 10 Apr 2018 16:42:43 +1000, Trevor Wilson
wrote:
Here's a question that stumped me back in the old slide rule days:
A coaxial cable, having an inner diameter of 0.0254mm (0.001") and using
an insulator with a dielectric constant of 2.56, is yo have a
characteristic impedance of 2,000 Ohms. What must be the outer conductor
diameter?
https://www.rfcables.org/coaxcalculator.html
 Select inches.
 Plug in any number for outside dia (D) trial an error.
 Plug in 0.001 for inner diameter (d).
 Plug in 2.56 for permittivity (er) (same as dielectric constant
in this example).
 Punch "calculate"
I used 1,000,000 inches for outside diameter and still obtained only
776 ohms. 1,000,000,000 inches yielded 1035 ohms. I don't think it's
going to make it to 2,000 ohms unless the coax cable is absurdly huge.
Almost sounds like an OLD ("slide rule") homework problem....
Jonesy
