Danny Richardson wrote:
. . .
Additionally, checking feed line balance by measuring current using
RF amp meters of each leg of open line will not accurate due the fact
that RF amp meters do not give any phase information. Roy corrected me
on that some time ago.

The thing to do is run both conductors through a single ferrite core
(type 43 is fine) -- you can squeeze them together or use a short piece
of two close spaced two conductor wire. Wind a secondary of 10 turns,
and terminate the secondary with about 50-100 ohms. Measure the
secondary voltage with an RF voltmeter (diode, capacitor, and DVM) or
scope. This directly measures the common mode current. Then compare that
to the reading you get with only one of the conductors going through the
core.

Roy Lewallen, W7EL