a. Forward/Reflected Power Discriminator. The forward and reflected power discriminators
operate in a similar manner, therefore the reflected power discriminator will be discussed first
with additional comments about the forward power discriminator discussed last.
A current sample is taken from rf line by transformer T1. This provides a voltage across load
resistor R4 proportional to the line current. This voltage is applied to the anode of diode CR2. At
the same time, a voltage sample is applied to the cathode end of the diode (derived by capacitor
divider C7 and C8). The transformer phasing and circuit constants are set so that when the rf line
is terminated in its characteristic impedance (50 ohms) the two samples are equal in phase and
magnitude. Therefore, diode CR2 does not conduct and the reflected power output is zero. Any
and diode CR2 conducts in proportion to the unbalance. The dc output voltage diode CR2 is
proportional to the reflected power and is sent to the 60W/6W power level network for eventual
monitoring by the front panel meter.