On 8/5/2016 11:49 AM, Danny Richardson wrote:
Identical current indication on a matched pair of thermocouple RF amp
meters do not necessarily mean the transmission is balanced as the
current magnitudes might be equal but the 180º phase difference isn't.
IF -- this is not always *necessary* -- we want to see if currents in a
2-wire feedline are unbalanced, I think a symmetrically placed ferrite
core of appropriate diameter around BOTH conductors, with a "secondary"
winding feeding a sensitive meter or 'scope (etc) is the way to go.
Also, we need to be aware that surplus thermocouple ammeter calibration
may not be as good as our other and modern instruments; OT's know this
-- and when to put up with it.
Don't be surprised if there's substantial CM current from other
sources; I've a local 10 kW expanded band AM station that occasionally
gives me fits with arcing (and for a time, melting) feedlines and
malfunctioning PA modules.
Cortland
KA5S
PS: My spell-checker suggests replacing "thermocouple" with
"thermonuclear".
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