4-14
888-2586-001
9/15/06
WARNING: Disconnect primary power prior to servicing.
Platinum Z16HD+
Section 4 Overall System Theory
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IPA Forward Power (IPA FWD PWR). A sample of the IPA forward power is taken
by the directional coupler (shown right after K3 on the schematic) and detected by
CR1. The DC voltage at TP1 will therefore be relative to the IPA output. This is sent
to the controller for monitoring and main/alternate IPA switching.
4.4.2.7
Air Flow Sensing
Airflow is sensed as the difference in temperature between a heated sensor, RT1, and an
ambient sensor, RT2 on the IPA Backplane Boards. RT1 is actively biased via R3 which
will cause a steady increase in temperature with no air flow. Under normal operation,
the voltage difference between the two sensor outputs will stabilize at some value
depending on the amount of air flow. If the airflow is reduced or non-existent, then RT1
will heat up increasing its voltage output, whereas RT2 will stay the same. At about
25% of nominal air flow the voltage difference between the two sensors will reach a
threshold where the controller will turn the fan to high speed to compensate for the
reduced airflow. If the airflow is still insufficient after switching the fan to high speed,
the transmitter will be shut off.
4.4.2.8
IPA Interlocking
The signals IPA1_PCB_OK and IPA2_PCB_OK are the interlock signals for the IPA
boards. The interlock connections on the IPA board (and the PAs as well) are shorter
than the other pins. This causes the interlock connection to break before the RF contacts
when the module is unplugged. This gives the controller time to shut off the IPAs (via
the IPA gate voltage, IPA1_GATE) so that the connector contacts do not arc.
4.4.2.9
IPA Power Divider (3dB Hybrid)
The IPA power divider is actually a 3dB hybrid which splits the IPA output into 2 equal
amplitude signals 90 degrees out of phase to drive the Z Planes at J5 and J6. Remember
that the output of the Z Planes is recombined using another 3dB hybrid which requires a
relative 90 degree phase angle between the two input signals. The reject port on the
hybrid is connected to an external Reject Load (JP3 is not installed) mounted in the
bottom plate of the PA compartment directly behind the IPA Backplane Boards. The
hybrid is integrated onto the IPA Backplane Board.
4.4.3
Z-Plane Combiner/Divider Boards
There are four Z-Plane Combiner/Divider assemblies in the Z16HD+ transmitter, A, B,
C and D. These two assemblies provide all inputs to and outputs from the PA modules.
The Z Plane is the overall term for the combination of the Combiner and Divider
boards. There is a separate schematic for each part of the Z Plane in the schematic
package. The first page of each schematic is identical and is a block diagram of the
entire Z Plane.
Summary of Contents for Platinum Z16HD+
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