The Slow Typer's Reply (hello echo echo echo)
Although this calculator was designed for coaxial feedlines, it also works for balanced line length from antenna to transmatch, or from antenna to short coax jumper connnected to a transmatch. You simply process the calculator results as follows:
(Resulting coax length in feet x 450 ohms)/450 ohms = ladder line length in feet
The final figure will give you a balanced line length that should easily be handled by a good external transmatch.
Be sure that you scroll to the bottom of the page after using the calculator; there you will find an easy-to-understand explanation of the concept.
Built-in antenna tuners are generally less tolerant of a mismatch, so you'd want a feedline length in multiples of a half-wave (current maximum points). That would be approximately 32', 64', 96', etc, although some slight adjustment might be required to compensate for variations in velocity factor.
And, quite seriously with full intent to be very helpful, you really can find a wealth of information at Cecil's web site: (W5DXP)
Last edited by K9ZMD; 07-17-2011 at 06:50 PM.