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Buck wrote:
I am a little confused, so bare with me..... I put up an antenna with 50 ohm of impedance. I feed it with any length of 300 ohm feed less than 1/2 L. Then I run 1/2 L of 50 ohm feed to the radio and I have the 50 ohm match? Nope, 50 ohms is only one of an infinite number of impedances you might encounter. For 50 ohms, you feed it with 1/2WL of 300 ohm feedline. This is similar to (but not exactly like) a G5RV used on 20m. I put up a 300 ohm antenna. I feed it with 300 ohm twin lead for less than 1/2 L and 1/2 L of 50 ohm feedline. Is this a 50 ohm match? Nope, you cannot transform the impedance of a 300 ohm antenna using 300 ohm feedline. You need reflections to cause an impedance transformation. A 300 ohm antenna impedance is not within the green doughnut area below. The range of impedances that can be matched with a length of 450 ohm ladder-line are represented by the green doughnut at: http://www.qsl.net/w5dxp/smith.htm The impedances outside the green area cannot be matched by only one 450 ohm matching section. The area in the doughnut hole cannot be matched by only one 450 ohm matching section. -- 73, Cecil, http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
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