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Re: [TowerTalk] Low SWR

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] Low SWR
From: Blair S Balden <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Mon, 01 Feb 2010 09:30:47 -0500
List-post: <">>
Hi Andy,
These values are important because SWR is a measure of how well the input 
impedance of your antenna system matches the output impedance of your 
xmtr/feedline.  Maximum transfer of power will occur when the output impedance 
of one stage matches the input impedance of the next stage.  Most of our radio 
equipment is designed with an output impedance of 50 ohms.  If this 50 ohm 
output impedance is connected to an antenna system with an input impedance of 
exactly 50 ohms, you get maximum power transfer and lowest SWR (1 to 1).  
Impedance is made up of resistance and reactance  (it's the vector sum of 
these).  Reactance comes in two forms, inductive and capacitive.  The total 
amount of reactance you have depends on your operating frequency and how much 
inductance and capacitance there is.  Inductive reactance acts opposite to 
capacitive reactance.  The two forms can be made to cancel each other out, thus 
reducing the total net reactance.  Changing the net reactance of the antenna 
system changes its impedance, which in turn will change the SWR.
Anyway, this is the way I understand it.  I'm sure others on here can shed more 
light on the subject.
Best regards,
Blair NP2F

----- Original Message -----
From: Andrew <>
Date: Sunday, January 31, 2010 11:29 am
Subject: [TowerTalk] Low SWR

> I have read that Reactance(X), Capacitance(C), and Inductance(L) 
> readings at
> Low SWR is useful info, how so?
> 73,
> Andy
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