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The following email was posted to the "Low Power Amateur Radio Discussion Group"

In my opinion it says it all as far as SWR is concerned.

(Ron Stark's added later note: In all cases the transmitter power was 100 watts)
(Ian Purdie's added note: My thanks to Ron, KU7Y for kind permission to reproduce his posting)

Subject: Re: Parallel Lines (was Re: loop formula)
Date: Sun, 23 May 1999 15:04:39 -0700 (PDT)
From: Ron Stark xxxxx@xxxxx.edu>
To: "Low Power Amateur Radio Discussion" <xxxxl@xxxx.EDU>

Hi All,

I'd like to offer something to help dispell the idea that a high SWR keeps power from getting to the antenna.....

If you can get a copy of Reflections by Walter Maxwell, do so! Or get the QST back issues on CD.

Chapter 4 was printed in QST October, 1973.

In it he talks about the Conjugate Mirror. I have also seen this talked about as the Conjugate Match. Larson antennas sent out an interesting paper a few years ago.

Leaving out the math, let me make this note....

When RF is reflected back down the feed line because of a
mismatch at the load, where does it go???

Does it all just fall out of the feed line?? No.

Does it all turn to heat in the transmitter?? No.

Does it just "disappear" into thin air?? No.

Most of it adds to the power from the transmitter and goes back to the antenna where it's used along with all the other power.

An example that Maxwell shows is using 175 feet of RG8 with a 1:1 match and a 3:1 match. There is a difference of 5.72 watts in how much power gets to the antenna in the two cases. That's 0.288 dB and is less than 1/12 of one S unit. He calls that difference insignificant and I agree.

I don't disagree with trying to get things as good as you can but I often see too many people that react by not putting up any antenna because they feel that what they were going to do just will not work!

Antennas are, to me, the biggest mystery of this whole hobby. I just can't believe that any of them can work!

Lets see.....I guess I should add that not everyone agrees with everything that Maxwell had to say!

Enjoy,

73, Ron, SOWP 5545M,

.........KU7Y.....ARCI #8829.....Monte "Ron" Stark.....
....ku7y@sage.dri.edu...........Washoe Lake, Nevada....
....QRP-L #17...ARS #49...NorCal #330.....NRA LIFE.....



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