[Elecraft] Balanced solution for KAT500 tuner?

[Adrian]

It comprises as per conjunction;  the input;

http://www.palstar.com/manual_bt1500a.pdf

"Input balun 1:1 current type balun

Impedance Range 2500 +/- j2500 160 m to 20 m
(assuming Resistive load) 1000 +/- j1000 17m to 10m

A single-ended L-network - the most common variety - uses a certain value of
inductance (L) and a certain value of capacitance (C) to effect a match at a
particular
frequency for a particular antenna feedline impedance and length. For
coaxial cable systems, the single-ended L-network provides the lowest loss
of
any network matching system. However, one limitation is that with the
capacitor
on the antenna side of the coil, the system is limited to antenna terminal
impedances
greater than about 50 Ohms. If we wish to use the single-ended network
with a balanced feedline, we have to add a balun on the output side of the
network.
Baluns work best with very low values of reactance on their output
terminals,
a condition that is difficult to obtain with most antennas that use parallel
feedlines.
The balanced version of the L-network overcomes this limitation by providing
a
true balanced output directly from the network. For a particular antenna,
operating
frequency, and transmission line impedance and length, the matching circuit
requires the same total circuit inductance and the same output capacitance
as the
single-ended network. However, the balanced circuit divides the inductance
into
two equal series portions, one in each leg of the network. The shunt
capacitor has
the same value in both versions of the L-network.

Unlike the single-ended L-network, the legs of the balanced L-network are
both
above ground potential. Hence, both the input and antenna sides of the
network
are balanced. In order to accommodate the single-ended transmission line
from
the transmitter, the tuner places a 1:1 choke (current) balun between the
input
side of the network and the transmitter coax connector. The balun converts
the
unbalanced input from the transmitter to a balanced condition for the
network.
As well, it suppresses currents that might otherwise appear on the braid of
the
transmitter cable."

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of David Gilbert
Sent: Sunday, 30 September 2012 10:57 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Balanced solution for KAT500 tuner?


Sorry for any confusion.  I thought you were trying to say that a balanced
antenna tuner with a balanced current choke was generally more efficient
than an unbalanced tuner with a balanced current choke.  Was that your
intent?  If so, why?

73,
Dave   AB7E




On 9/29/2012 3:37 PM, David Gilbert wrote:
> I don't believe that is necessarily true.  Can you cite a reference to 
> back up that statement?  Or at least describe in physical terms (Q, 
> currents, voltages, component loss, etc) why that would be so? I'm 
> honestly curious what the difference would be.
>
> 73,
> Dave   AB7E
>
>
>
> On 9/29/2012 2:13 PM, Adrian wrote:
>> 1:1 current balun has proven more efficient in conjunction with the 
>> appropriate balanced (matchbox style)tuner.
>>
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net 
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Robert G. 
>> Strickland
>> Sent: Sunday, 30 September 2012 4:26 AM
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] Balanced solution for KAT500 tuner?
>>
>> Jim...
>>
>> Is there anything to be gained in putting a 1:1 "balanced isolator" 
>> at the feed point of an antenna that is fed by a "parallel wire" feed 
>> line? Does such an arrangement achieve feed line isolation while 
>> preserving the ability of such an antenna to be driven on various 
>> bands other than its resonant frequency? Thanks for your input.
>>
>> ...robert
>>
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