Platinum Z5 CD - 8-Way Divider; 8-Way Combiner

888-2408-002 4-9
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
The RF output of the Z-Plane board connects directly to the 3dB hybrid where it is
combined with the output of the second Z-Plane Combiner/Divider board. The Z
plane boards are identical, but the outputs connect to opposite ends of the 3dB
hybrid (one at the top and one at the bottom). This requires that one of the Z Planes
be physically inverted.
4.3.4.1 8-Way Divider
Refer to the Divider schematic for the following. Each 8-Way Divider is a 2-stage
Wilkinson divider. The 8 way dividers are located on the Z-plane boards in the
center of the PA assembly.
The input to the divider is first divided into two equal outputs at approximately 35
ohms by a two-way Wilkinson divider with a 70.7 ohm isolation resistor, R9. Each
of these outputs (each end of R9) is then divided into 4 outputs in a 4-way
Wilkinson divider.
The Wilkinson dividers contain terminating resistors which dissipate no power
when all of the outputs are correctly loaded, but if a PA is removed, resulting in an
open-circuit on an output, the Wilkinson circuit and the load resistors act to keep the
input impedance of the splitter near the nominal value of 50 ohms. Each output from
each 8-Way Divider is fed to the input of one PA Amplifier boards, at J1 - J8.
4.3.4.2 8-Way Combiner
Refer to the Combiner schematic for the following. Each 8-way combiner consists
of two 4-way Wilkinson combiners, called FOURSOMES, followed by a 2-way
Wilkinson combiner which combines the outputs of the two Foursomes. The
Foursomes are split up as follows:
• A1, A2, A3 and A4 - Front Right Foursome
• B1, B2, B3 and B4 - Front Left Foursome
• A5, A6, A7 and A8 - Rear Left Foursome
• B5, B6, B7 and B8 - Rear Right Foursome
The Wilkinson combiners include isolation loads (ISO loads) which dissipate no
power if all PA outputs are equal and in phase. These resistors are located on the
Isolation Boards and labeled RT1-RT8. The ISO resistors connect to the points
labeled E1-E8 on the Combiner schematic. If any input is lost due to failure of a PA
module, the associated ISO load will dissipate some power; approximately 150
watts, until the RF switch on the Isolation board disconnects the ISO load and
grounds that point (E1-E8) on the combiner. This now looks like an open to the 4-
way combiner output at E9 or E10 (the input to the 2-way combiner).