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Re: [TenTec] SWR VS Power Loss

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] SWR VS Power Loss
From: Ken Brown <ken.d.brown@hawaiiantel.net>
Reply-to: ken.d.brown@hawaiiantel.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 04 Jul 2008 08:24:39 -1000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

> 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. 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.


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