[Elecraft] ATU efficiency and the Elecraft T1

[Stuart Rohre]

Another answer for Darrell, is that a balun is designed to see equal antenna 
halves either side of it.  (on its balanced side).

There is no advantage to using one on an end fed dipole.

If you were to feed with coax, to an end fed dipole, and that coax is 
quarter wave long, you would transform the high impedance of around 3000 
ohms at the end of dipole to something lower at the other end of coax.  But, 
because the coax is low impedance and the dipole end is high, you would have 
a lot of feedline loss from The SWR reflections.

That is the reason, low loss (with high SWR) parallel high impedance lines 
like ladder line or open wires are used to feed end fed dipoles.  You use a 
link at the tuner to couple to such lines.  The tuner has a tank coil and 
capacitor to tune it to each band of use.

The link has fewer turns than the LC tank, but can also have a cap for 
tuning.

If you had any RF issues on the tuner metal case, you could try a 1:1 cable 
choke formed by ferrite beads strung on a short coax, and that would then 
couple to the balanced line, if you were not using link coupling to the 
radio tuner.  However, use of the link and the isolation it affords, also 
reduces the pickup of suburban electrical noise.

Stuart
K5KVH