On Sun, 6 Jun 2010 14:21:16 -0700 (PDT), Keith Dysart
wrote:

The 100W forward and 50W reflected have no relation to actual powers

From HP Journal V4n5-6:

The multi-hole coupler design has now
been extended to a 3 db coupler, that is, a
coupler in which half the power entering the
main guide is coupled into the auxiliary
guide.
....
The -hp- multi-hole couplers consist of
two sections of wave guide mutually coupled
by two rows of coupling holes (Fig. 2).
Power entering the input arm of the coupler
flows down the main guide and divides at the
coupling mechanism. Part of the power con
tinues down the main guide where it will be
incident on any device connected at the end
of the guide. The other part of the power is
coupled into the auxiliary guide. It is a prop
erty of directional couplers that the power
coupled into the auxiliary guide flows essen
tially in only one direction. In the -hp- coup
ler, this power flow is in the same direction
as the power in the primary guide.
....
R E F L E C T O M E T E R S E T - U P
....
Two directional
couplers are connected back-to-back
as shown.
*******
I will leave it to the readership to imagine why.

73's
Richard Clark, KB7QHC