334 pages. ISBN: 0964470721
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Preface
Amateur radio communication has progressed in many ways since its beginning in the early 1900's. General communications progressing from spark to CW and voice from AM to FM and SSB. Similarly, data communications as a mode of amateur communications has progressed from using onoff keying (OOK) to FSK, and from RTTY to more modern modes of communications (synchronous and errorcorrecting). There has been a lack of good technical background material in amateur radio literature on the principles and design of synchronous digital modems.The wealth and quality of literature in the professional world in the subject area is astounding, but much of it may not be readily accessible to the radio amateur, whether for reasons of advanced mathematics, or simple lack of availability.
In writing this book, the aim has been to bring a concise group of topics covering a broad spectrum of amateur synchronous digital communications subjects to print in one place, and to make it readily accessible to the radio amateur. This text aims to present the information in a clear and straightforward manner, with the maximum use of graphical and computerassisted aids, and with a minimum of rigorous mathematical theory. However, digital communications deals with the application and solution of statistical phenomenon, and a minimum background is necessary. Where practical, the appendices provide short summaries of some of the important mathematical concepts that will be needed in understanding certain areas.
Overall, the field of digital communications could be generally broken into two categories: bandwidthlimited communications and powerlimited communications. Much of the professional literature focuses on the former, while in practice the amateur is many times concerned with the latter. This text focuses more on the subject of powerlimited communications and emphasizes, through examples, the circuits and problems of the latter category of applications.
With time and the increasingly more crowded HF bands, however, the radio amateur will adopt more sophisticated data modems, offering higher throughput and narrower bandwidth operation under the demanding propagation conditions of the HF medium. This trend has already started and should accelerate as the cost of technology, particularly Digital Signal Processing, continues to decrease. So, this text includes information on the subject areas of DSPbased modem filters, and on forwarderrorcorrecting codes, whose use by the radio amateur will become dominant within a few short years. While the data rate of VHF and UHF communications will increase, it is expected that, for the radio amateur, these will remain powerlimited applications for some time.
In the preparation of this text, I have relied on the study of a number of exceptionally well written textbooks, and to the IEEE literature in the area, and these should be consulted whenever more depth or broader interest is desired. I would like to thank the reviewers of the text for many helpful comments, related both to the readability of the material, ...
(more in the book!)

Thomas C. McDermott, N5EG
Dallas, Texas August 25, 1995
Tom's first book signing party!
(January 5th, 1997)Tom McDermott, N5EG, Greg Jones, WD5IVD, Lon Cecil, WB5PKJ, Bob Stricklin, N5BRG, and John Koster, W9DDD (left to right)
Chapter 1  Introduction
 Definition of Information
 Source Entropy
 Fundamental Data Capacity
 Signal to Noise ratio  Eb/No
 Block Diagram of the Communication System
 Review / Definition of Some Key Concepts
 Eye Pattern
 Signal Constellation Diagram
 Chapter 1  References
Chapter 2  Additive White Gaussian Noise (AWGN)
 Definition of AWGN Noise
 Gaussian Distribution
 Calculating the BER given AWGN
 Generating a BER Curve
 Relation of Power Spectrum and AWGN
 Computing Noise and Signal Magnitudes
 Chapter 2  References
Chapter 3  Antipodal, Orthogonal, and Nonorthogonal Signaling
 Antipodal Signaling
 Orthogonal Signaling
 Nonorthogonal Signaling
 Analysis of FSK signaling
 Orthogonal Waveforms
 Orthogonal FSK Demodulators
 Chapter 3  References
Chapter 4  Carrier Transmission
 FSK  Frequency Shift Keying
 FFSK  Fast Frequency Shift Keying
 mFSK  mary FSK
 PSK  Phase Shift Keying
 mPSK  mary Phase Shift Keying
 OQPSK  Offset QPSK
 Received Phase Ambiguity
 Performance of PSK modulation in the presence of AWGN
 ASK  Amplitude Shift Keying
 MSK  Minimum Shift Keying
 OFDM  Orthogonal Frequency Division Multiplexing
 OFDM based on mary FSK
 OFDM based on ASK
 AFSK  Audio Frequency Shift Keying
 Summary
 Chapter 4  Reference
Chapter 5  Frequency and Impulse Response of Optimum Modem Filters
 Optimum filter criteria
 RaisedCosine Filter Responses
 Filter Response Partitioning
 Filter Impulse Response
 Filter Response to an Isolated Data Bit
 Eye Pattern Generation
 Equivalent Noise Bandwidth
 Some Frequency Response Defects
 ImpulseResponse Length Truncation
 Detailed StepbyStep Procedure
 DolphChebychev Transmit Pulses
 Chapter 5  Reference
Chapter 6  Matched Filters
 Matched filter for Rectangular Pulses
 Matched filter for SquareRoot RaisedCosine Transmit Pulses
 Use of the Matched Filter Symmetry to Equalize a Channel
 Chapter 6  Reference
Chapter 7  Data Codes
 Basic Data Codes
 DCBalance (One's Density) of the Code
 Scrambling
 Forward Error Correcting (FEC) Codes
 Linear Block Codes
 AWGN Performance of Linear Block Codes
 Statistical Performance of Linear Block Codes
 Other Properties of FEC Codes
 Interleaving the Codewords
 Golay Codes
 Longer Codes
 ReedSolomon Codes
 Convolutional Codes
 Decoding the Convolutional Code
 Convolutional Decoders
 Viterbi's Algorithm
 Summary of Viterbi Decoder
 Chapter 7  Reference
Chapter 8  Data Slicer and the Slicing Level
 Slicing Level Determination
 Source Statistics
 NonScrambled Data
 NRZICoded HDLC Calculations
 Scrambled Data Calculations
 Binomial Distribution
 Fixed SlicingLevel Methods
 DSPBased SlicingLevel Determination
Chapter 9  Clock Recovery
 The Importance of Accurate Clock Position
 Methods to Recover the Clock
 ClosedLoop Clock Recovery
 Clock Recovery Filters
 Filter Transfer Function
 ModulationBased Clock Recovery
 Chapter 9  Reference
Chapter 10  Carrier Recovery
 Deriving a Carrier Reference
 Carrier Generation by Rectification
 Carrier Generation by Multiplication
 Other Methods of Carrier Generation
 2PSK Carrier Recovery  Costas Loop
 Chapter 10  Reference
Chapter 11  Phase Locked Loops for Carrier and Clock Recovery
 Closed Loop Response
 Open Loop Response
 Lead Lag Filter
 Higher Order Loop Filter
 Parasitic Poles
 PLL Loop Lock time
 PLL Noise Bandwidth
 Types of Phase Detectors, Lockin Range
 Control Loop Dynamic Range
 Chapter 11  Reference
Chapter 12  Frame Alignment and Data Carrier Detect
 General Data Carrier Detect (DCD) Acquisition
 DCD and Frame Alignment based on Message Content
 Median Time to False Frame Declaration
 Maximum Average Reframe Time
 Going Out of Frame
 Other Message Content
 Framing on Short Transmissions
 Chapter 12  Reference
Chapter 13  Propagation Channel Models
 VHF and UHF Channel Models
 MinimumPhase and NonMinimumPhase Fades
 Rayleigh fading
 Circular Polarization
 Wideband Data Channels
 Rules of Thumb
 HF Channel models
 Signaling Rate Bounds
 HF Channel Simulation
 Coefficient Properties
 Bit Error Rate Performance of Rayleigh Faded Path
 Diversity Reception
 Approaches to HF Modem Design
 RTTY  Live With the Errors
 AMTOR  Simple Error Detection and Retransmission
 AX.25 Packet Transmission  300 baud HF
 More Recent Developments
 GTOR
 Pactor II
 Clover II
 Future Improvements
 Chapter 13  Reference
Chapter 14  Automatic Request for Repeat (ARQ)
 Simple ARQ
 Hybrid ARQ
 Performance of ARQ
Chapter 15  Testing Considerations
 Bit Error Rate vs. Received Signal Level
 Baseband BER Test
 Butterworth Calibration Filter
 Radio Characterization for Data
 Radiobased Test
 FSK  Transmitter Characterization
 Other Transmitter Characterization
 FSK  Receiver Characterization
 System Characterization
 Theoretical Eb/No vs. Received Signal Level (RSL)
 PseudoLevel Error Detection Margin
 Adjustment Aid  'Click' box
 Bit Error Rate Test Statistics
 Chapter 15  Reference
Appendix A  Some Useful Probability Distributions
 A.1 Probability of Events.
 A.2 Histograms, Probability Density, Cumulative Density
 A.3 Uniform Distribution
 A.4 Binomial Distribution
 A.5 Gaussian Distribution
 A.6 Poisson Distribution
 A.7 Rayleigh Distribution
Appendix B  PseudoRandom Binary Sequence (PRBS) Generators
 B.1 Properties of a PRBS
 B.2 Construction of the PRBS Generator.
 B.3 Autocorrelation Properties
 B.4 Self Synchronization
 B.5 Self Synchronous Scrambler and Descrambler
 B.6 Binary Polynomial Arithmetic
 Appendix B  Reference
Appendix C  Discrete Fourier and Inverse Discrete Fourier Transforms & Complex Numbers
 C.1 The Fourier Transform and the Impulse Response
 C.2 Complex Number Representation
 C.3 Description of a Signal using Complex Notation
 C.4 Complex Conjugate
 C.5 Discrete Fourier Transform
 C.6 Power Spectral Density (PSD)
 C.7 Symmetry Requirement for Frequency Response
 Appendix C  Reference
Appendix D  Correlation, Convolution, and Laplace Notation for Filters
 D.1 Convolution and Multiplication
 D.2 Convolution
 D.3 Frequency and Impulse Response
 D.4 Correlation
 D.5 Cross Correlation
 D.6 Autocorrelation
 D.7 Complex Signals
 D.8 Laplace Notation for Complex numbers
 Appendix D  Reference
 TAPR Information
 Index