[Elecraft] High power tuner

[Don Wilhelm]

A balanced version of the "T" network is a physical monstrosity 
requiring that both ends of the capacitors float, but is possible.  The 
T network has the greatest matching range, but suffers from false 
matches resulting on high circulating currents in the tuner.

A balanced "L" network should not be difficult to produce, but if I may, 
I would like to put in a plug for my favorite balanced tuner which is 
IMHO is the old fashoined parallel (or series) resonant tank circuit 
using a link coupler.  No balun required, but it does not lend itself 
easily to band switching.  As a single band tuner, it is the ultimate 
IMHO, and the venerable Johnson Matchbox was an attempt to make that 
basic circuit bandswitchable. The Matchbox has some limitations in the 
matching range it can handle.  My Johnson Matchbox will only be pried 
from my hands over my "cold dead body" - I do not use it much, but it 
really is handy for creating artificial antennas with SWR in the 
workshop, and it works quite well as a bandpass filter when that is needed.

73,
Don W3FPR

On 11/26/2011 6:48 PM, Joe Subich, W4TV wrote:
> On 11/26/2011 6:00 PM, Vic K2VCO wrote:
>> The balanced output is not referenced to the case. So the balun is
>> functional when feeding a balanced line, not shorted as you suggest.
> You are correct, that the balun is not shorted when feeding a balanced
> antenna.  However, in that configuration it will *only* function as a
> common mode choke (if it is not constructed as a voltage balun).
>
> Any antenna connected to the "balanced" terminals will still not be
> truly "balanced" as it is not possible to generate a balanced output
> at the output of an unbalanced network by forcing balance at the input
> of that network.  It is quite likely that a "balun" at the input of
> an unbalanced network will only increase circulating currents (and
> losses) in the network.
>
> 73,
>
>      ... Joe, W4TV
>
>