Is it possible to reverse calculation of coax transformation ratio?

[4L4AGU]

Say we have some antenna, feed with 12 meters of RG-213 coax. Impedance at TX end is say R28-jX 200, frequency is 7.1 mhz. Knowing coax type and it's characteristics, can we calculate it's transformation ratio, so we'll know what is the antenna impedance at feedpoint?

[N3OX]

Sure, it can be solved for. One easy way to do that is to use VK1OD's calculator:

http://vk1od.net/calc/tl/tllc.php

Choose your coax type, length, and frequency and choose "Zin" in the drop down "Mismatch" menu instead of "Zload"

I get a load impedance (at the antenna) of 1.3-j62 for your stated parameters.

73
Dan

[4L4AGU]

Heheh, I've being used that calculator for ages, but haven't thought about it that way. Thanks. The parameters I provided were just example, no real system.