Gene Fuller wrote:
OK, we are getting somewhere. According to the equation, we know that
interference has the same units as irradiance. Interesting. Does that
mean that interference doesn't work for fields? Are there multiple
definitions for interference?

My IEEE Dictionary is 130 miles away so I cannot look
up the technical definition for interference. The units
of irradiance are watts per unit area. In a transmission
line, we can consider the unit area to be constant and
simply drop the units of area. The resultant "irradiance"
equation for transmission line power is:

Ptotal = P1 + P2 + 2*SQRT(P1*P2)cos(A)

2*SQRT(P1*P2)cos(A) is the interference term in watts
where A is the angle between the two interfering fields.

This is all explained at: http://www.w5dxp.com/energy.htm
If the above equation is followed, adding powers is easier
than superposing voltages and then calculating power.
--
73, Cecil http://www.w5dxp.com