Section III - Implementation
FM Considerations


Antennas and Combining

Analog FM Signals

Multi-station Combining

Combining Digital Signals in the FM Band
Common Amplification
        Co-Synthesis
        Low-Level Combining
High-Level Combining
        The High-Level Combiner
        Why a 10-dB Combiner?
        Efficiency and Heat Load
        Mismatch and Isolation
            Turn-around Loss
            Minimizing Unwanted Interaction
            Directivity
            Isolation
Split-level Combining
        Efficiency
        Considering the Options
        Isolation

Combining with Antennas
The IBOC-to-Antenna Path
Dual-Feed Antenna
Separate-Antenna Operation
        Separate-Antenna Research
        Separate-Antenna Regulation
Multi-Station Antenna Systems
        Common-Line IBOC to Multi-Station Combiners
        Separate-Line IBOC and Multi-Station Combining

Crest Factor and Peak Power in Hybrid IBOC Transmission
OFDM Peak to Average
Relate OFDM to Analog
OFDM Peak to Analog Peak
OFDM RMS to Analog RMS
Hybrid Crest Factor
Difference Between Hybrid and Analog Crest Factors

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Chapter 13: TABLES
13.1 High-Level Combiner Power Budget
13.2 Comparison of Combining Efficiencies
13.3 IBOC-to-Antenna Paths
13.4 Three Stations Tested for Separate-antenna Performance
13.5 Multi-station IBOC Combining Options
13.6 Computation of Hybrid IBOC Peak-to-Average Power Ratio

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Chapter 13: FIGURES
13.1 Composite Baseband (Source: NRSC)
13.2 Creation of an FM Signal
13.3 Spectra of Frequency Modulated Broadcast Signals
13.4 Branch Combiner
13.5 Balanced Combiner
13.6 90-degree Hybrid
13.7 Co-synthesis and Low-Level Combining
13.8 High Level Combining Diagram (Courtesy of Shively Laboratories)
13.9 Combiner Signal Paths
13.10 Split-level Combining Diagram
13.11 Harris Coupling Coefficient Calculator on the World Wide Web
13.12 Common-Line and Separate-Line Topology
13.13 Quadrature-fed FM Antenna
13.14 Field Test Measurements of Digital-to-Analog Power Ratios for Combined- and Separate-Antenna Operation (Source: NAB)
13.15 IBOC and Multi-station Combiners
13.16 Illustration of Peak-to-RMS Relationships of Two Waveforms

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