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Re: [TenTec] SWR VS Power Loss

To: tentec@contesting.com
Subject: Re: [TenTec] SWR VS Power Loss
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Reply-to: geraldj@storm.weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 04 Jul 2008 12:56:28 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
On Fri, 2008-07-04 at 08:24 -1000, Ken Brown wrote:
> > Found this nice table.  Thought I would pass it along.  
> > http://www.firestik.com/Tech_Docs/SWRLOSS.htm
> >
> >
> >   
> "SWR (Standing Wave Ratio) affects the power output of your radio. The 
> following table shows the effect of SWR for a transmitter with 4 watts 
> of transmitted power."
> Using a standard power level of 4 watts, they are not talking to the 
> amateur QRP crowd, because those guys generally consider 5 watts to be 
> the regular QRP level. Who do you suppose this chart was made for? 
> Apparently for people who want some simple (not necessarily accurate) 
> explanation of why they should care about SWR, without the complications 
> of transmission line loss included. A quick truncation of the url to 
> find the home page reveals who their audience is.
> Checking a couple of values on this table, it appears the assumption is 
> that all of the reflected power just gets dissipated at the transmitter 
> and does not get reflected back towards the antenna.

But the data presented is just plain wrong except for the 1:1 case. All
the rest is trash. Its the same quality data as CB antenna gain claims.

> Just a single 
> reflection at the mismatch, and the reflected power is lost, that's it! 
> If there was a real good circulator (isolator) at the transmitter, that 
> would be nearly true.
73, Jerry, K0CQ

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