[Elecraft] Balun for K-1

[Ron D'Eau Claire]

In the KISS tradition, I'd like to throw in an observation made today
with my doublet fed with open wire line. I was using a T-match ATU with
a balun and measuring the current in each feeder to see how well
balanced they were. 

A mystery arose. Just for fun, thinking about the post earlier today
about ignoring the balun,  I disconnected the balun and simply connected
one side of the open wire feed to the hot output of the ATU and the
other feeder to the case of the ATU. The currents in the two feeders
remained in balance! Connecting an earth ground (strap about 4' long to
a ground rod) to the case right where one feeder connected did not
affect the tuning or the current in the feeder. 

I checked this on all bands from 40 through 10. On a couple of bands the
balance was horrible. I should point out that my doublet is not well
balanced, physically. Space limitations have one end of the doublet
closer to the ground than the other. There is an obvious difference in
the impedance presented at the ATU by each half, if they are fed
individually as end fed wires. It is more apparent on the higher
frequencies. So the balance is never "perfect" under any conditions. But
the installation is probably typical of a great many Ham setups where we
don't have two supports at 60 feet out in the clear to string the
antenna between. 

On only one or two bands did the balun help the balance. On the rest the
feed currents were more or less in balance and they were about the same
with or without the balun. The bands where the balun seemed to do the
most good were those where the feeders presented a relatively high
impedance to the ATU, as evidenced by the current being very low. 

As someone pointed out earlier today, you may not need a balun at all! 

 I've used a doublet fed with open wire line a great deal over the
decades, but always with a true link-coupled balanced ATU, so I never
had an occasion to try this experiment before. Whenever I ran a balanced
line with a single-ended ATU I assumed (bad word, "assume") that I had
very poor balance in the feed line and it was radiating as much as any
other part of the antenna. Not necessarily so, it seems...

Ron AC7AC
K2 # 1289