Balanced line operators need a pair of identical thermocouple amp
meters arranged so as to be easily inserted in the line to measure the
current on each side simultaneously. It is probably easier to do this
if the operator isn't using the brown plastic window line. Genuine
ladder line, separate wire conductors held by spacers every few feet
is preferable, or better yet, open wire line -- parallel conductors
stretched taught and held in place with knob insulators on posts and
antenna support structures.
Once a balanced current measuring method is in place, readings can be
taken to ascertain the line balance (at times on a dead band) and
experimentation can be done to see what aids in balancing the
currents on the line. Grounding objects, or floating them, detuning
antennas--sometimes a near field unbalanced antenna not in use can be
connected to a run of coaxial cable or capacitor to ground and that
will detune it and help with the current balance on the antenna under
test.
It all sounds onerous, but once you get into it, it is kind of fun.
Another important factor is the balanced to unbalanced matching
network. I have found that a link coupled network helps eliminate or
attenuate RFI because there is no direct conductive path from the
balanced line to the unbalanced feed in the shack. My matching
network sits indoors right at the window entrance where the ladder
line comes in.
73
Rob
K5UJ
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