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What's with this 18 foot thing, it's nonsense. There's nothing 'magical' about 18 feet of coax, and it seldom, if ever, has any meaningful use. It amounts to trying to 'tune' an antenna system with the length of feed line. The simplest/best way to do that is by tuning the antenna. Then, the length of feed line makes no difference at all. If the antenna isn't at least close to being tuned correctly then feed line length can make a difference (usually not a good one though).
Of course, it also goes back to a lack of knowledge of what SWR is and how meaningful it is/isn't. SWR deals only with impedance matching, doesn't tell you anything about how 'tuned' an antenna. To understand that you have to know what impedance is composed of, how those 'parts' of impedance affect things, what's meaningful and what isn't.
I know that isn't what you want to hear but it doesn't affect the fact that you need to know that stuff. And until you do you are wasting your time and money.
Have fun.
- 'Doc

<blockquote data-quote="W5LZ" data-source="post: 392725" data-attributes="member: 129">What&#039;s with this 18 foot thing, it&#039;s nonsense.&nbsp; There&#039;s nothing &#039;magical&#039; about 18 feet of coax, and it seldom, if ever, has any meaningful use.&nbsp; It amounts to trying to &#039;tune&#039; an antenna system with the length of feed line.&nbsp; The simplest/best way to do that is by tuning the antenna.&nbsp; Then, the length of feed line makes no difference at all.&nbsp; If the antenna isn&#039;t at least close to being tuned correctly then feed line length can make a difference (usually not a good one though).Of course, it also goes back to a lack of knowledge of what SWR is and how meaningful it is/isn&#039;t.&nbsp; SWR deals only with impedance matching, doesn&#039;t tell you anything about how &#039;tuned&#039; an antenna.&nbsp; To understand that you have to know what impedance is composed of, how those &#039;parts&#039; of impedance affect things, what&#039;s meaningful and what isn&#039;t.I know that isn&#039;t what you want to hear but it doesn&#039;t affect the fact that you need to know that stuff.&nbsp; And until you do you are wasting your time and money.Have fun.&nbsp;- &#039;Doc</blockquote>

[QUOTE="W5LZ, post: 392725, member: 129"] What's with this 18 foot thing, it's nonsense. There's nothing 'magical' about 18 feet of coax, and it seldom, if ever, has any meaningful use. It amounts to trying to 'tune' an antenna system with the length of feed line. The simplest/best way to do that is by tuning the antenna. Then, the length of feed line makes no difference at all. If the antenna isn't at least close to being tuned correctly then feed line length can make a difference (usually not a good one though). Of course, it also goes back to a lack of knowledge of what SWR is and how meaningful it is/isn't. SWR deals only with impedance matching, doesn't tell you anything about how 'tuned' an antenna. To understand that you have to know what impedance is composed of, how those 'parts' of impedance affect things, what's meaningful and what isn't. I know that isn't what you want to hear but it doesn't affect the fact that you need to know that stuff. And until you do you are wasting your time and money. Have fun. - 'Doc [/QUOTE]

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