Owen Duffy wrote in
:

....
Of course it doesn't matter, which unit system you use, but if you
start adding 'forward' and 'reflected' power in dBm because it is real
convenient, you have peformed a vector addition of power. Is that
valid?

I should have said "...you have peformed a flawed vector addition of
power..."

Owen

Owen Duffy wrote:
I should have said "...you have peformed a flawed vector addition of
power..."

The correct method of adding power comes to us from the
field of optics in the form of the irradiance equation.
If we multiply irradiance by the cross-sectional area of
coax, we get power.

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

where 'A' is the angle between the electric fields
of the two phasors.
--
73, Cecil http://www.w5dxp.com