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## [TowerTalk] Elevated vertical and transmission line basics

 To: [TowerTalk] Elevated vertical and transmission line basics "Bob Alexander" realex2@verizon.net Mon, 26 Dec 2011 08:43:53 -0600 mailto:towertalk@contesting.com>
 ```Good morning guys, The elevated vertical thread is covering what I have been lecturing about for 15 years. Several times a year I do a presentation at Hamfests or club meetings I call "Transmission Line Basics". The essential points I try to make are: 1. There are two impedance values on every transmission line. One is the Characteristic impedance which never changes unless the cable has been damaged or in rare cases has been designed to change characteristic Impedance along its length. The other is the impedance of the signal on the line. 2. A line terminated in a value equal to its Zo will have a signal Z all along its length equal to the load Z with the only changes due to line losses. 3. Since the signal Z is constant on the matched line, a signal applied to the line will have the same voltage, current and phase all along its length. Therefore no SWR 4. It's when a line is not terminated in a value equal to its Zo that things get interesting 5. A mismatched line is an impedance transformer. There is no point on the line where the signal Z will equal the line Zo. It may get close due to losses but never the same. 6. Since the Z constantly changes, the signal voltage and current change along the line length. The relationships of the changing voltage or current is SWR. 7. The Z mismatch seen by a transmitter is the value at the line input, not at the load. Sorry for repeating things several people have already said on this thread but like I said, I like to talk about transmission lines. 73, Bob, W5AH _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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