[Elecraft] Baluns and 450 ohm line

[Stuart Rohre]

Well put Ron!  Your expansion of the discussion on balance reminded me to
point out that besides the unbalance of doublets with unequal legs such as
the Windom, the equal legged doublet can introduce imbalance (unequal
feedline currents).  How does this happen?  In some locations, you might
have run one leg of the doublet over a roof of a building, while the other
leg is in the clear, with nothing under it.

Or, one leg might run closer to some overhead electrical wires than the
other leg.  There are various such influences that can upset the line
current equality you desire when using parallel feeders.  At least in this
area, I find RF ammeters still available at ham swaps, and a pair of matched
models is a good investment, if one wants to seriously explore the issues in
using parallel lines.  They were common tune up aids in the single wire
military aircraft radio outputs.
The idea is to upset both sides of the parallel line equally, by inserting
two ammeters one in each leg of the feeder, and compare the current
indications.  It helps to mount them in a non conducting box, and otherwise
avoid introducing losses and non symmetry to the measurement setup.
72,
Stuart K5KVH