[Elecraft] OT Tuner ranges

[Bob McGraw K4TAX]

My findings and applications agree with Victor's statement that a 1:1 
current balun, specifically a Guanella balun design with added common 
mode choke is the preference for using a tuner to feed a balanced or 
open wire line.    For the life of me, I have never been able to 
understand the general belief that a 4:1 balun should be used with open 
wire feed line.   Maybe it is the "400 ohms" or "450 ohms" that is 
attracted to the number "4" in the balun ratio that is the attraction.   
I view it the case of the  "tuner lemmings" where one started it 
{incorrectly as it may be} and the rest followed.

By now most of us are well aware of the need for a 4:1 Guanella balun to 
be wound onto two separate cores, not just a single core.  
Unfortunately, most balun manufacturers are clueless and continue to 
promote these single core baluns for OCFD antennas.   A few (e.g., Balun 
Designs and Palomar Engineers) have either dual-core’s or even hybrid 
baluns.

The secondary reason that the single core 4:1 Guanella is not 
appropriate.    If you wrap both winding's onto a single core, each 
winding has half as many turns as when you wrap them onto separate 
cores.  Since inductance (and CMI) increases with the square of the 
number of turns, it is obvious that a single core balun could never work 
anywhere nearly as well as a dual-core balun.

But the primary reason is, in HF antenna applications, a 4:1 Guanella 
Balun wound onto a single core has no CMI at all; ZERO.  In fact it can 
even generate CMC.  (Source: G3TXQ).  Therefore, by definition, it is 
not even a balun at all. – Yes I have read Sevick too and he shows a 
single core 4:1 Guanella balun as well as a dual core, but he fails to 
explain the difference.  The single core will only work in applications 
that are 100% ground independent, or “floating.”    No HF antenna 
located here on mother earth is ground independent; thus the single-core 
4:1 Guanella is not suited for HF antenna applications.

As to tuner ranges, add a length of coax or insert a piece of equipment 
in the path and the Z  +j   is now different. Hence the appearance match 
range will be different.

73

Bob, K4TAX





On 5/24/2018 3:05 AM, Victor Rosenthal 4X6GP wrote:
> I believe that the K3 tuner does have more range than the one in the 
> KAT500.
>
> My experience with this kind of system (tuner -> balun -> open wire 
> line) is that the 1:1 balun works much better from the point of view 
> of losses and choking off RF in the shack.
>
> What do you mean that the 4:1 balun has less range on 160 than the 
> 1:1? If you are saying that the SWR curve is broader, then that could 
> just be because of losses in the balun.
>
> 73,
> Victor, 4X6GP
> Rehovot, Israel
> Formerly K2VCO
> CWops no. 5
> http://www.qsl.net/k2vco/