[Elecraft] Balun for KAT2

Sun Jan 13 19:42:00 2002

Jonathan,
While I didn't conduct testing to measure losses, I reasoned that a simple
W2DU choke type balun would have lower loss over a transformer type balun
wound over a toroid.  As such, that's what I'm using.  I connect out of my
K2/KAT2 through a short coax run to a Radio Works choke balun.  Then
directly to 450 ohm window line to my dipole, cut for 40M.  I let the KAT2
match the "mess" unconcerned about the short length of coax, but knowing
the choke balun will do the unbalanced-to-balanced conversion by
minimizing the current flow on the coax shield.  This combination seems to
tune OK on 40M on up.  This is my "portable" setup.

My next experiments will be with the "end fed half wave".  Primary goal:
reduce weight even further, down to a backpackable weight and size.
Another possibility will be a 300 ohm twin-lead dipole  -- e.g. QST, Feb
'02.

After reading W2DU's book "Reflections" I've really changed my view on
SWR.  Mr. Maxwell clearly demonstrates that SWR alone is not a reliable
indication of good antenna match (or performance).  In fact, a low SWR may
really mean high losses, low efficiency and other undesirable conditions!
So, I've begun to look toward improving efficiency -- not minimizing SWR.
Why?  Well briefly, a 50 ohm dummy load will indicate a 1:1 SWR, yet
radiate poorly!  All power entering the transmission line is radiated,
independent of SWR -- less losses (in coax, ground, etc.).  As such, I've
looked at elements in my antenna system that are low loss.  The W2DU type
choke balun is in this class.

73,
Steve
aa8af

"Jonathan Taylor, K1RFD" <[email protected]>
Sent by: [email protected]
01/12/2002 08:22 PM

        To:     <[email protected]>
        cc:
        Subject:        [Elecraft] Balun for KAT2

I just set up an 80m dipole with ladder line (600 ohm), and may soon
become
a believer in the open-wire feed.

When using it with an ATU such as the KAT2, with low power, what is the
most
efficient way to convert the KAT2 unbalanced output to the balanced line?

My first inclination is to build a small toroidal balun inside a box and
run
a short length of coax to the rig.  But I have also read that this type of
balun can be lossy when working through an impedance (on the balanced
side)
far from the design impedance.  (Is the coax length critical?)

Has anyone used the so-called "current baluns" offered by RadioWorks?