Topband: W8ji ATR-10 design 160M?

[Tom W8JI]

Respectfully, the X match is nothing but a  common T-match with a fixed 
capacitor in one leg. In a normal T-match, operating Q can be varied over a 
wide range by adjusting L/C ratios.  By restricting range of one leg, 
operating Q range is limited. So it actually **is** a T match, it just has 
two adjustable branches instead of the more common three adjustable 
branches, restricting the operating Q range and matching range.

The ATR10 is more like the common old Johnson matchbox, with the exceptions 
instead of a link it has a tap and it is single ended. The tap sets the 
operating Q, just as the link ratio sets the operating Q in a Matchbox. 
This restricts the matching range and operating Q range.

Tuners that fix the operating Q at a certain value, or limit the operating Q 
range, will always restrict matching range. The operating Q restriction 
limits peak voltages or currents by preventing grossly improper adjustments, 
but the very same thing that limits voltages or current by definition also 
limits matching range.

An L network limits matching range the most of any network for a give range 
of component values, but also limits operating Q the most. It has only one 
operating Q available at any given impedance ratio. The Q varies with load 
impedance. You cannot have too much Q, or it won't match.

This is, unfortunately, the way the world works. Everything is a tradeoff of 
matching range, cost, complexity, and power rating. No single network, just 
like no single balun, is all things to all cases.

The widest matching range for a given cost is a T network with two 
adjustable capacitors and one shunt inductor. Unfortunately, people think 
(and articles repeat) the silly idea that the proper way to tune is to start 
with capacitors at half and tune for maximum receive.

Most of any improvement centers around preventing people from doing 
something silly, by limiting what they can do. There isn't any magic 
circuit.

Tom

----- Original Message ----- 
From: "N4XM Paul D. Schrader" <n4xm at iglou.com>
To: "Jim GM" <jim.gmforum at gmail.com>
Cc: "topband" <topband at contesting.com>
Sent: Wednesday, October 16, 2013 11:01 AM
Subject: Re: Topband: W8ji ATR-10 design 160M?


> Jim,
>
> I did not make the comments you said I made below.  And the XMATCH Antenna
> Tuner is NOT a "T" match.
> It is a patented circuit.  This unique circuit is a United States Patent.
>
> And see http://n4xm.myiglou.com
>
> Paul  N4XM