Topband: Zo of an individual CAT5 twisted pair

[Tom W8JI]

> Actually, the balance of a circuit is defined by its impedances to the 
> reference plane.

By function, if the voltages and currents are balanced (currents equal and 
opposite and voltages to surroundings equal and opposite), the system is 
balanced.

It is important to point out to everyone that simply looking at current, 
which is what most (if not nearly all) people and articles do, cannot tell 
us if the system is balanced or not.

Worse yet, in many places, articles and "test equiment" looks only at scalar 
currents. QST articles on baluns and transmission line testing, and even 
things like articles about using meters to measure balance and a 
transmission line balnce meter sold by MFJ, look only at scalar current.

We can have balanced impedances to the "reference plane" in the line, or 
space around a line, and still have imbalance in the **system**.  On the 
other hand, if we have equal and opposite currents through the conductors 
along with equal and opposite voltages to the line surroundings (or 
"reference plane"), we have a balanced system.

The important point is voltage from each conductor to surroundings is what 
really determines the gender of balance, because ideally both coax and 
twinlead have equal and opposite currents in the two conductors.

73 Tom