Cecil Moore wrote:
Jim Kelley wrote:
Evidently then you haven't adequately familiarized yourself with the
nature of the equations that you use.

The last term in the following power density equation
is known as the "interference term". If it is positive,
the interference is constructive. If it is negative,
the interference is destructive.

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

Ptotal = 50w + 50w + 2*SQRT(2500)cos(45)

Ptotal = 100w + 100w(0.7071) = 170.71w

The interference term is 70.71 watts of constructive
interference indicating that there must exist 70.71 watts
of destructive interference elsewhere in the system.
If the constructive interference happens at an impedance
discontinuity in a transmission line in the direction of
the load then there must be an equal magnitude of
destructive interference toward the source.



I share Tom B's suspicions. Since Cecil's analysis is leading to
physical absurdities such as "watts of destructive interference" and
vagueries such as "elsewhere in the system", it means that something is
wrong. It could be either in his statement of the problem, the
suitability of his chosen method of analysis, or the way Cecil is
applying that method; or any combination of the above.

Either way, it is Cecil's tarbaby, and nobody else needs to get stuck to
it.

The rest of us can continue to use the methods that have existed for a
hundred years to account for the voltages, currents and phases at any
location along a transmission line, and at any moment in time.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek