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Let's say you are using 100 feet of old RG-8 coax and that it has a line loss of 3 db for that 100 feet at your transmit frequency. Place your SWR meter at the antenna end of the coax. Your transmitter is putting out 100 Watts, into a perfectly matched (1:1) antenna. Your reflected power is 0%. your radiated power is 50 Watts, due to the line loss of 3 db.

Let's increase your SWR to 2:1. That means that about 10% of the power that reaches your antenna is reflected and 90% radiated. OK, 45 Watts radiated and 5 Watts reflected. By the time that 5 Watts gets back to the transmitter, it is down to 2.5 Watts and is reflected back to the antenna. By the time that it gets back to the antenna, it is down to 1.25 Watts. 90% of this is radiated, or 1.12 Watts. Add this to the 45 Watts and you have 46.12 Watts. This process continues until no more measurable power reaches the antenna. In this case, you might get another .03 Watts to radiate.

What does this mean? That of the 50 Watts that reached the antenna the first time, 46.15 Watts was radiated. Or, put another way, 46.5/50=93% of the power radiated. Wait a minute! didn't 194's chart say that we lost 10% (Actually it says 11%, I just rounded it to 10% for simplicity)?

Not all of the reflected power is lost. But, the silver lining of this cloud is, that it shows what a demon that line loss can be. We only have to use better feed line and our radiated power will jump dramatically, even with poor SWR. Also, it shows that if you place the SWR meter at the transmitter, you will get an erroneous reading. In this example your meter would read that 2:1 SWR as 1.6:1. All because of line loss.

Change that old RG-8 to a good quality RG-213 and your radiated power will jump to about 80 Watts. Go to 600 ohm open wire line and your power radiated will be an astounding 97 Watts. All with the same 10% reflected power, due to the 2:1 SWR. Even with a 10:1 SWR, the 600 ohm line will still get over 89 Watts out of the antenna. This is why good tuners are such a good deal.

Try this coax loss calculator and see what I mean.

Line Loss Calculator

Rich

<blockquote data-quote="Hamin&amp;#039; X" data-source="post: 72567" data-attributes="member: 1374">Let&#039;s say you are using 100 feet of old RG-8 coax and that it has a line loss of 3 db for that 100 feet at your transmit frequency. Place your SWR meter at the antenna end of the coax. Your transmitter is putting out 100 Watts, into a perfectly matched (1:1) antenna. Your reflected power is 0%. your radiated power is 50 Watts, due to the line loss of 3 db. Let&#039;s increase your SWR to 2:1. That means that about 10% of the power that reaches your antenna is reflected and 90% radiated. OK, 45 Watts radiated and 5 Watts reflected. By the time that 5 Watts gets back to the transmitter, it is down to 2.5 Watts and is reflected back to the antenna. By the time that it gets back to the antenna, it is down to 1.25 Watts. 90% of this is radiated, or 1.12 Watts. Add this to the 45 Watts and you have 46.12 Watts. This process continues until no more measurable power reaches the antenna. In this case, you might get another .03 Watts to radiate.What does this mean? That of the 50 Watts that reached the antenna the first time, 46.15 Watts was radiated. Or, put another way, 46.5/50=93% of the power radiated. Wait a minute! didn&#039;t 194&#039;s chart say that we lost 10% (Actually it says 11%, I just rounded it to 10% for simplicity)?Not all of the reflected power is lost. But, the silver lining of this cloud is, that it shows what a demon that line loss can be. We only have to use better feed line and our radiated power will jump dramatically, even with poor SWR. Also, it shows that if you place the SWR meter at the transmitter, you will get an erroneous reading. In this example your meter would read that 2:1 SWR as 1.6:1. All because of line loss.Change that old RG-8 to a good quality RG-213 and your radiated power will jump to about 80 Watts. Go to 600 ohm open wire line and your power radiated will be an astounding 97 Watts. All with the same 10% reflected power, due to the 2:1 SWR. Even with a 10:1 SWR, the 600 ohm line will still get over 89 Watts out of the antenna. This is why good tuners are such a good deal.Try this coax loss calculator and see what I mean.<a href="http://www.ocarc.ca/coax.htm" target="_blank">Line Loss Calculator</a>Rich</blockquote>

[QUOTE="Hamin' X, post: 72567, member: 1374"] Let's say you are using 100 feet of old RG-8 coax and that it has a line loss of 3 db for that 100 feet at your transmit frequency. Place your SWR meter at the antenna end of the coax. Your transmitter is putting out 100 Watts, into a perfectly matched (1:1) antenna. Your reflected power is 0%. your radiated power is 50 Watts, due to the line loss of 3 db. Let's increase your SWR to 2:1. That means that about 10% of the power that reaches your antenna is reflected and 90% radiated. OK, 45 Watts radiated and 5 Watts reflected. By the time that 5 Watts gets back to the transmitter, it is down to 2.5 Watts and is reflected back to the antenna. By the time that it gets back to the antenna, it is down to 1.25 Watts. 90% of this is radiated, or 1.12 Watts. Add this to the 45 Watts and you have 46.12 Watts. This process continues until no more measurable power reaches the antenna. In this case, you might get another .03 Watts to radiate. What does this mean? That of the 50 Watts that reached the antenna the first time, 46.15 Watts was radiated. Or, put another way, 46.5/50=93% of the power radiated. Wait a minute! didn't 194's chart say that we lost 10% (Actually it says 11%, I just rounded it to 10% for simplicity)? Not all of the reflected power is lost. But, the silver lining of this cloud is, that it shows what a demon that line loss can be. We only have to use better feed line and our radiated power will jump dramatically, even with poor SWR. Also, it shows that if you place the SWR meter at the transmitter, you will get an erroneous reading. In this example your meter would read that 2:1 SWR as 1.6:1. All because of line loss. Change that old RG-8 to a good quality RG-213 and your radiated power will jump to about 80 Watts. Go to 600 ohm open wire line and your power radiated will be an astounding 97 Watts. All with the same 10% reflected power, due to the 2:1 SWR. Even with a 10:1 SWR, the 600 ohm line will still get over 89 Watts out of the antenna. This is why good tuners are such a good deal. Try this coax loss calculator and see what I mean. [url=http://www.ocarc.ca/coax.htm]Line Loss Calculator[/url] Rich [/QUOTE]

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