[Elecraft] how did I calculate the loss?

[John Buck]

Hi Charles,

I enjoyed reading the documentation you referenced at 
http://www.njqrp.org.  This is great construction and test documentation 
of an excellent design.  It is recommended reading for anyone 
considering building a balun.

As I read the documentation, the balun you studied was terminated in 50 
ohms on the input side.  When used in a typical K2 application with 
internal antenna tuner, the input and output impedance may be much 
higher (or lower).  What can be said about the performance when driven 
by and antenna tuner to match impedance's such as found with a G5RV type 
dipole fed with various lengths of 300 or 450 ohm twin line?  My problem 
is with the varying conditions for multiband use.  Yes properly applied 
Baluns are not very lossy.

In the case you quote, it appears that you were looking at the 
efficiency of the 4:1 balun when terminated with 50 ohms on the input 
and 700 ohms on the output.
If used with the K2 KAT2 or KAT100 the input impedance might be nearer 
200 ohms.  What impact does this have on the loss and on the saturation 
characteristics?

Aloha,
John KH7T

Charles Greene wrote:

> It's another of those bits of folk lore, that a balun is lossy except 
> at the design impedance.  I did some extensive loss measurements on a 
> 4:1 current balun working into 700 ohms at a high reactance instead of 
> 200+j0, and found the efficiency was 94% (it was 97% on a 200 +j0 ohm 
> load).  Find a place in the open wire line where the SWR is less than 
> 5:1 and place your balun there.  My tests are documented at: 
> http://www.njqrp.org/
>