9/15/06
888-2586-001
4-3
WARNING: Disconnect primary power prior to servicing.
Section 4 Overall System Theory
Platinum Z16HD+
4.2
RF Flow Block Diagram Description
Figure 4-1 is a block diagram of RF flow of the Platinum Z16HD+ transmitter. Not
shown on this diagram is the power supply and control/monitoring associated with the
advanced Controller and Diagnostics system.
4.2.1
RF Source
Once again, due to the different hardware configurations, there are many possibilities of
RF signal origination within the transmitter. The RF chain may begin with either an
HDx-FM exciter, or a BoostPro amplifier output. Or, in FM backup mode it may begin
with any one of several Harris FM exciters. To simplify terminology this RF origination
will be called RF Source by the controller, and throughout this manual. However, there
may be times when text discussing certain circuitry may still use the original term
exciter. Also, there may be certain pieces of hardware that still contain the word exciter
in the part description, on its silkscreen labeling, or as part of the schematic
representation.
4.2.2
PA and IPA Modules
There are 16 PA modules and 2 IPA modules in the Z16HD+ Transmitter. All of the
modules are identical and interchangeable. Each module is made up of two separate
amplifiers, one on each side of the heat sink, which are referred to as PAs. The term
module is reserved for the combination of heatsink and 2 PAs. The modules are Hot-
Pluggable which means they can be removed and replaced while the transmitter is
running. They are also symmetrical which means that they can be inserted into the
transmitter with either side facing up (they cannot be inserted wrong).
4.2.2.1
IPAs
The Z16HD+ has 2 IPA Modules, each of which is made up of 2 power amplifiers or
PAs. The IPA Modules are identical to, and interchangeable with, the PA Modules. The
2 IPAs on each IPA Module operate in Main/Alternate mode, meaning that only one of
them (per module) is active at a time. The block diagram shows that IPA_AB1 and
IPA_CD2 are the normally active amplifiers. RF switching on the input and output of
the amplifiers is activated by the controller if a fault is sensed in one of the active IPAs.
The IPAs can also be switched manually using the IPA Status Menu in the Diagnostics
Display [STATUS D,B]. Both IPAs are switched together for optimal phasing. For
example if IPA_AB1 failed, the controller would switch to IPA_AB2 but it would also
switch to IPA_CD1. Each IPA Backplane Board has a phasing adjustment to minimize
system imbalance if an IPA is replaced.
The active IPA outputs are split using 3dB hybrids built onto the IPA Backplane Boards.
Each hybrid provides 2 equal amplitude outputs 90 degrees out of phase. The two
Summary of Contents for Platinum Z16HD+
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