TX Line Calculator

Version 1.0  26 April 2015

Summary

This is a special purpose calculator which performs simple transmission line
calculations. Given three line parameters, the Widget calculates the value of a
fourth. Two formulae are used, one for coaxial cable, the other for parallel
line.

Instructions When the Widget is started, it displays a window with four fields.

Enter data into the three green fields, then press the RETURN or ENTER key. The
Widget computes a fourth value and displays it in the fourth field.

Which of the four values is to be computed can be set in the Widget's
preferences or by clicking the amber button, which reveals a menu from which the
output mode (output field) can be chosen.

Coaxial Cable and Parallel Line

The Widget uses two formulae, one for coaxial cable, the other for parallel
line. The formula to be used can be chosen in the Widget's preferences or by
clicking the green button, which reveals a menu from which the input mode
(Coaxial Cable or Parallel line) can be chosen.

For coaxial cable, the formula used is: Z0 = Zv * ln(o / i) / (2 * π * sqrt(e)),
where Zv is the characteristic impedance of a vacuum, o and i are the outer and
inner cable radii, e is the relative permittivity of the dielectric, and Z0 is
characteristic impedance of the transmission line.

For parallel line, the formula used is: Z0 = Zv * ln(s/r) / (π * sqrt(e)). where
Zv is the characteristic impedance of a vacuum, s and r are the line separation
and line radius, e is the relative permittivity of the dielectric, and Z0 is
characteristic impedance of the transmission line. The value of Zv is taken to
be 376.73031346177066 ohms.

Units of Measurement

Because the measurements of length only appear in the
ratios (o / i) and (s / r), they can be in any units desired, provided the same
units are used for both.

License

The Tx Line Calculator is Copyright © 2007 Harry Whitfield (G6AUC). This program
is free software; you can redistribute it and/or modify it under the terms of
the GNU General Public License as published by the Free Software Foundation;
either version 2 of the License, or (at your option) any later version. This
program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details. You
should have received a copy of the GNU General Public License along with this
program; if not, write to the Free Software Foundation, Inc., 51 Franklin St,
Fifth Floor, Boston, MA 02110-1301 USA

Widget Concept, Coding and Documentation

Harry Whitfield <g6auc@arrl.net