[Elecraft] Balanced solution for KAT500 tuner?

[Adrian]

A UK G call did a graphed efficiency comparison test with the 1:1 coming out
on top. I will post it when re-found.

Also from
http://www.theladderline.com/doublets-ladder-line-and-automatic-remote-tuner
s  ; (spell-checked)

"There is also some debate about whether the balun should be a 1:1 or 4:1. I
think 4:1 has been quite popular in the past. This perhaps comes from the
thought that the ladder line is higher impedance than coax so we need to
step down to get it closer to the coax impedance. On the forums, people who
have modelled the antenna with software like EZNEC seem to make a fairly
compelling argument that a 1:1 balun is more likely to present an impedance
within the range of the tuner over a wide range of frequencies. The
impedance will depend on the length of the ladder line so it's a bit of a
gamble but I'm getting good results from a 1:1 current balun.
 
After doing some reading and playing with a home brew balun, I finally took
the lazy way out and splashed out on a serious balun. It's a DX Engineering
BAL050-H10-AT. It's not cheap but I think it was a good investment. I don't
have any hard evidence to show how good it is compared to a cheaper balun
but I have a feeling that it contributes to the good performance I get with
this antenna. I've had absolutely no "RF in the shack" or similar problems
even at the old QTH when I had the ladder line coming into the shack.
 
An interesting fact that I learned from the forums is the reason ladder line
works more successfully than coax in a multiband situation like this. The
common belief is that ladder line "doesn't care" about high SWR. It's true
that ladder line usually has lower loss than coax at a given SWR but that's
not the whole story. Another rather simple factor is that the characteristic
impedance of ladder line is higher than coax so therefore, for a typical
wire antenna over a wide range of frequency, the average SWR on ladder line
tends to be lower than it would be with coax and that helps keep the loss
low."

-----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 8:37 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Balanced solution for KAT500 tuner?


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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