[TenTec] balanced feedline light bulb test

[Stuart Rohre]

No, you piggyback the clip leads spaced apart onto bare wire of the parallel
line on one side.  ie clip, wire lead, bulb, wire lead, clip.  Start with
clips say a foot apart.  You may have to experiment to get spacing to get
bulb to glow at your power level.  This was usually used with 10's of watts.

Now, you clip a second bulb onto the other wire of the parallel line with
same spacing to compare bulb brightness which is proportional to current in
each individual line.

If you have insulated parallel twin lead or ladder line, you may have to use
capacitance pick ups of metal folded half around the one side of the ladder
line.  Or cut into the insulation, which is the disadvantage of this method.

It is attempting to replicate the current measurement by placement of RF
ammeters in series with each leg of parallel transmission line.

See illustration in ARRL HANDBOOK and Antenna Book from 1957 on for many
years.
-Stuart
K5KVH