9/15/06
888-2586-001
4-5
WARNING: Disconnect primary power prior to servicing.
Section 4 Overall System Theory
Platinum Z16HD+
allowing greater redundancy. This also allows the PA Modules to be HOT-
PLUGGABLE, meaning that a PA module may be removed while the transmitter is
operating.
If a module is removed, the short interlock pins disconnect first, causing a 120mS
system mute. The RF switches on the Isolation Boards (the 2 for the affected module)
are activated isolating the modules output from the combiner allowing the transmitter to
operate with the module removed. At the end of the 120mS mute the system returns to
normal operation. With only one module removed the system should return to near full
power by automatically raising the APC (Automatic Power Control) voltage (a listing
of “Transmitter Power vs. Module Failures” is given in Section VI, Troubleshooting.
4.2.3
"5kW" Hybrid Combiner
The outputs from Z-Plane A and Z-Plane B are combined in a 3dB hybrid which is
specially fit in between the two Z-Planes. The same is true for Z-Planes C and D. Since
the Z-Planes already have the required 90 phase relationship they will combine at the
hybrid output with little or no power lost as long as all PAs are operating normally. Each
3dB hybrid has a reject or ISO load labeled ISO_AB and ISO_CD. They are attached
directly to the top of each hybrid. If there is any imbalance (phase or amplitude)
between the two Z-Plane outputs, AB or CD, the ISO load absorbs the imbalance. An
example would be a failed PA causing one Z-Plane output to be lower than the other. A
removed PA module would not cause an imbalance at this point since it would affect Z-
Planes A and B (or C and D) the same. The greater the imbalance, the higher the
temperature of the ISO load. A temperature sensor on the load monitors the temperature
for the Controller. If the imbalance is too great the controller will foldback the
transmitter power to keep the ISO load temperature within tolerance. The outputs of the
two "5kW" hybrids are -90 and -180 degrees (respectively) and attach directly to the
"10kW" hybrid, located below the power blocks.
4.2.4
"10kW" Hybrid Combiner
The two hybrid outputs are combined in the last 3dB hybrid, for a final output. This
combiner is located in a flat aluminum box below the power blocks, and just above the
power supplies in the Power Supply Compartment. This hybrid also has its own ISO
load called ISO_ABCD since it is combining the outputs from all four Z-Planes. The
temperature of this load is also monitored and used to detect imbalances between the
outputs of the two Power Blocks.
The transmission line Harmonic Filter attaches to the top rear of this box and connects it
to the output flange on the top rear of the transmitter. The Harmonic Filter has 3
directional couplers. One is for Forward Power, one is for Reflected Power and the third
is left available for on site use as a Demodulator or analyzer sample. The couplers are
designed for at least 30dB directivity.
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