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Re: [TowerTalk] balanced line loss on a mismatched antenna

To: "Gary Slagel" <>, "TowerTalk" <>
Subject: Re: [TowerTalk] balanced line loss on a mismatched antenna
From: "Paul Christensen" <>
Date: Mon, 27 Feb 2012 19:11:08 -0500
List-post: <">>
Another thought...

Although you cannot vary the 450-ohm SWR, you can vary the line's 50-ohm SWR 
by changing line length to possibly reach close to 50+j0 at the line input, 
and perhaps without the need for the tuner.  The key to this exercise is 
knowing the antenna feedpoint Z from EZNEC.  The rest is easy to solve.

Paul, W9AC

----- Original Message ----- 
From: "Gary Slagel" <>
To: "TowerTalk" <>
Sent: Monday, February 27, 2012 6:07 PM
Subject: [TowerTalk] balanced line loss on a mismatched antenna

Hi all,

I need some input on line loss when using 450 ohm balanced line to feed a 
mismatched antenna.

According to an online loss calculator, if I have a 150ft run of 450 ohm 
balanced line and an SWR of 100 to 1 I have about 3.5 db of loss at 7.0 mhz. 
If I have a 10 to 1 SWR that same feedline will have about a .5 DBI loss. 
I'm thinking of a w8jk style antenna that has 2 44ft elements on a 16ft boom 
fed with 450 ohm balanced line for 40 meters. EZNEC says the swr at the 
antenna will be over 100 to 1. I think I can tune the antenna with the 
feedline and get it down to a more reasonable level, maybe 10 to 1, at the 
tuner end. Then the tuner will tune it to resonance so the xmttr can put its 
full load into.

Question is, since the swr is 10 to 1 at the radio end of the feedline but 
100 to 1 at the antenna end of the feedline, am I going to see the 3.5 db 
loss from a100 to 1 swr or the .5 dbi that a 10 to 1 swr would give me.

Thanks for your input!

Gary Slagel

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