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Re: [Amps] Autotuner for Amp Input

To: n1rj@roadrunner.com, amps@contesting.com
Subject: Re: [Amps] Autotuner for Amp Input
From: TexasRF@aol.com
Date: Sat, 9 Oct 2010 06:45:55 EDT
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Hi Roger, 50 ohm to 50 ohm matching can be done with two components by  
using them as a parallel tuned circuit.
 
I have had good results on 6m using a parallel tuned circuit and taping the 
 inductor for both the input and load connections to achieve step up, step 
down,  or no step transformations. Minimum Q is determined by tube input C 
and strays,  maximum Q can be set as desired by the L/C ratio of the circuit.
 
This is not a great solution for multiband amplifiers but sure works well  
for singlebanders.
 
73,
Gerald K5GW
 
 
 
 
 
In a message dated 10/8/2010 11:43:44 A.M. Central Daylight Time,  
n1rj@roadrunner.com writes:

Here is  a good site for calculating impedance matching  networks:

http://bwrc.eecs.berkeley.edu/research/rf/projects/60ghz/matching/impmatch.h
tml

In  the old days when exciters had tubes and tuned outputs, most linear 
amps  had
input Qs of from 1 to 2 or thereabouts. With the advent of solid state  
exciters
without tunes outputs, the requirement seems to be for a  higher Q to 
provide the
flywheel effect. Measures recommends a Q of  5based upon Eimac  
recommendations:

http://www.somis.org/D-amplifiers4.html

An  L network matching 50 Ohms to 60 Ohms (3x3-500Z) has a Q of .44! I  
addition,
an L network will not match 50 Ohms to 50 Ohms. This requires  a 3 
element network.

73,  Roger























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