Historic Papers

Historic Papers

AM

• AM Transmitter Performance Without Filter Chokes, Wallace W. Wahlgren, Electro Engineering Works, San Leandro, CA. From 1964 National Elecronics Conference Proceedings. Scanned by John Lyles. 1.6MB
• The WLW 500kW Transmitter, Proceedings of the Institute of Radio Engineers, Volume 22, Number 10, October 1934. Describes the design and installation of the transmitter. Among the unique features are use of high level plate modulation with a class B modulator (with modulation reactor), a series fed vertical radiator, ability to operate at reduced power with portions of the transmitter removed from operation for repair, and use of coax between the transmitter and the antenna tuning unit. Another intersting feature is that the tower lighting AC wiring is enclosed in the output inductor of the antenna tuning network. A similar technique has been used relatively recently to get a variety of signals (AC and RF) across the base insulator of series fed towers. File provided by Stanley Adams. File size 5.4MB.
• A New High-Efficiency Power Amplifier for Modulated Waves - by W. H. Doherty, Bell Telephone Laboratories, Presented at the annual convention of the Institute of Radio Engineers, Cleveland, Ohio, May 1936.
• Ground Systems As A Factor In Antenna Efficiency - by G.H. Brown, R.F. Lewis, and J. Epstein of RCA, Proceedings of IRE, June 1937.
• The Pulse Duration Modulator: A New Method of High-Level Modulation in Broadcast Transmitters, H. Swanson, Gates Radio Company, IEEE Transactions on Broadcasting, December 1971. Scanned by John T. M. Lyles.
• Gates PDM Transmitters - High Level Plate Modulation without Modulation Transformers or Reactors, Hilmer Swanson, Gates Radio Company - 1972 NAB. Scanned by John T. M. Lyles.
• Modulation Systems for Amplitude Modulation - From the Edmund LaPort Archive (RCA 1920-1950) of the Smithsonian Museum of American History. Describes AM modulation systems including low level, class B high level, Doherty, and "out phasing" (AmpliPhase). Scanned by John T. M. Lyles.
• Powell Cathanode Modulation System, R. J. Rockwell, 1966. A system for high level, high efficiency amplitude modulation is described which avoids the use of a modulation transformer, thereby permitting the application of wideband feedback, resulting in very low distortion and a full power pass band of 20 to 20 000 Hz. File size: 2.6MB
• Technical Evolution of American Broadcast Transmitters - From the Edmund LaPort Archive (RCA 1920-1950) of the Smithsonian Museum of American History. A brief description of the history of AM broadcast transmitters and their manufacture. Scanned by John T. M. Lyles.
• A Plate Modulation Transformer for Broadcasting Stations, Loy E. Barton, Associate Professor of Electrical Engineering, University of Arkansas. Bulletin Number 8, Engineering Experiment Station, Fayetteville, AR, May 1930. Describes the design and advantages of the use of a modulation transformer for high level plate modulation. Includes transformer design for a class B modulator driving a class C RF amplifier. Does not include the use of a modulation reactor to remove DC magnetic flux from the transformer core. Scanned by John T. M. Lyles.
• Amplitude Modulation - 1973, Ronald Graiff, Allocations and RF Systems Engineer, American Broadcasting Company. Reviews the effects of AM modulation where positive peak is higher than negative (to FCC limit of +125%), carrier shift, etc. Scanned by John T. M. Lyles.
• Enhancing AM Signal Quality Through Improved Modulation Techniques, Brian C. Cox, Harris Corporation. Demonstrates how a PDM transmitter handles nonsinusoidal waveforms better than the typical plate modulated transmitter. Scanned by John T. M. Lyles.
• Performance Measurements and Test Techniques For Modern AM Broadcast Transmitters, Jeffrey Malec, Harris Corporation, Broadcast Division. IEEE Transactions on Broadcasting, June 1989. Discusses test techniques for AM broadcast transmitters including audio frequency response, thtal harmonic distortion, AM signal to noise, positive peak modulation capability, carrier shift, squarewave tilt and overshoot, audio intermodulation, transient intermodulation, out of band emissions, incidental quadrature modulation, CQAM L-R frequency response, efficiency, conducted emissions, temperature, humidity, altitude, line voltage variations and transients, electrostatic discharge, AC line phase imbalance and loss of phase, VSWR tolerance, and high voltage discharge into output network. Scanned by John T. M. Lyles.
• The Dependence of AM Stereo Performance on Transmitter Load Phase, Jerry M. Westberg, Westberg Consulting. This gives results of stereo performance done at 590kHz where a non-ideal load was rotated by use of a line stretcher. Scanned by John T. M. Lyles.
• Improving the Efficiency and Reliability of AM Broadcast Transmitters Through Class-E Power, David W. Cripe, Broadcast Electronics. This paper compares the operation of Class-D and Class-E power amplifiers and predicts how the performance and reliability of each is affected by the non-ideal conditions likely to occur in an AM broadcast transmitter. Scanned by John T. M. Lyles.
• Second Generation Techniques For AM Stereo Exciter Design, Edward J. Anthony, Broadcast Electronics. This paper reviews some of the improvements and new approaches developed by Broadcast Electronics during the design effort for the AX-10 exciter. Scanned by John T. M. Lyles.
• Spectrum Analysis - Amplitude & Frequency Modulation, local copy, HP Test & Measurement Application Note 150-1, 1996. Provides a nice explanation of why AM and FM generate sidebands, and how to use a spectrum analyzer to analyze AM and FM signals. 1.4M. Reproduced as authorized by Agilent Technologies. Contributed by Stanley Adams.
• Audio Signal Peak Energy Equalization - Patent 3,060,389 by L. R. Kahn, October 23, 1962. Basis for the Kahn SymmetraPeak
• Noise Free Radio - A proposal to run narrow band FM on the medium wave (AM broadcast) band by George W. Yazell, P.E.. Does not address relationship between FM bandwidth and demodulated signal snr. Uses relatively complex method of modulation and demodulation.

FM

• A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation, by Edwin H. Armstrong, Proceedings of the Institute of Radio Engineers, Volume 24, Number 5, May 1936. This paper, for the first time, demonstrates the noise reduction advantages of wide band FM over AM. Prior analysis explained that FM required a wider RF bandwidth with no advantage. The frequency modulation was created by generating a phase modulated carrier at a relatively low RF frequency, then running it through a series of frequency multipliers to arrive at the broadcast frequency (about 40MHz). A later design included a hetrodyne circuit so the broadcast frequency could be changed without having to retune all those frequency multipliers. The phase modulation is generated by adding the unmodulated carrier to the output of a balanced modulator shifted 90 degrees (quadrature amplitude modulation). The paper also discusses the use of both AM and FM subcarriers on the FM carrier. A suggested use of the subcarrier is facsimilie broadcasting (a predecessor to today's data broadcasting proposals). The paper includes the received image of the front page of the November 24, 1934 New York Times. File contributed by Stanley Adams. File size 2.7MB.
• A Receiver For Frequency Modulation, J. R. Day, Columbia University, as published in Electronics, June 1939. This is one of the very first of the commerical receivers, it rivals the REL and GE in performance and in circuit design. This type of receiver was built primarily for commerical use for those pioneer broadcasters. It was designed and described by a worker of the MHL in which EH Armstrong was director at this time and inventor of the System of FM Communications. Contributed by Stanley B Adams. 871k
• The Composite Signal - Key to Quality FM Broadcasting by Geoffrey N. Mendenhall, P.E., Broadcast Electronics, a tecnical paper oriented toward helping the station engineer better understand how the transmission system affects the composite signal. Scanned by John T. M. Lyles.
• Fine Tuning FM Final Stages, by Geoffrey N. Mendenhall, P.E., Broadcast Electronics, how tuning an FM transmitter affects FM sidebands and synchronous AM. Scanned by John T. M. Lyles.
• Early FM - Several New York Times articles on early FM including transition to the existing band in the late 1940s.

• FM Stereo Report and Order, 1961. Contributed by Mark Humphrey. File Size: 171kB. This R&O established the standard and rules for FM stereo operation in the US. The system numbers referenced in the document are:
  

  1 - Crosby-Teletronics Corporation
  2A - Calbest Electronics
  2B - Multiplex Development Corporation
  3 - Electrical and Musical Industries (EMI Percival)
  4 - Zenith
  4A - General Electric (identical to Zenith)
  5 - GE Alternate Proposal
  6 - Philco

• Installation Methods for Protecting Solid State Broadcast Transmitters Against Damage from Lightning and AC Power Surges, by John F. Schneider, Broadcast Electronics, Inc.. Scanned by John T. M. Lyles.
• A Study OF RF INTERMODULATION BETWEEN TRANSMITTERS SHARING FILTERPLEXED OR CO-LOCATED ANTENNA SYSTEMS, by Geoffrey N. Mendenhall, P.E., Broadcast Electronics. This paper describes a method by which the mixing loss between two FM transmitters can be accurately characterized. Manufacturers of transmitters can then supply this data to consultants and designers of filterplexed FM systems. Filterplexer characteristics, as well as antenna isolation requirements, can be tailored to the specific requirements of the transmitters being used. The end user can rest assured in advance of construction that the system will perform to specification without fear of overdesign or underdesign of the components within the system. Scanned by John T. M. Lyles.
• Optimum Bandwidth for FM Transmission by Edward J. Anthony, Broadcast Electronics, 1989. The purpose of this paper is to determine how much bandwidth is required for low distortion FM transmission, and at what bandwidth the point of diminished returns regarding distortion improvement is reached. Scanned by John T. M. Lyles.
• Transmitter Performance Requirements for Subcarrier Operation by John T.M. Lyles and Mukunda B. Shrestha, Broadcast Electronics. This paper discusses how the characteristics of the transmission system (bandwidth, linearity, etc.) affect subcarrier operation (crosstalk, distortion, etc.). Scanned by John T. M. Lyles.
• Design of Tube Amplifiers for Optimum FM Transmitter Performance by Mukunda B. Shrestha, Broadcast Electronics. This paper discusses various topologies of the input and output circuits of a vacuum tube power amplifier and analyzes their effects on the transmitter amplitude and group delay responses. Results of computer circuit analysis and actual measured data of a typical transmitter with two different topologies are compared. Design considerations for optimum transmitter performance to achieve the desired level of transparency to a wideband FM broadcast signal is also discussed including recommendations for compensating the group delay of the transmission system. Scanned by John T. M. Lyles.
• The Significance of RF Power Amplifier Circuit Topology on FM Modulation Performance by Mukunda B. Shrestha, Broadcast Electronics. This paper discusses various topologies of the input and output circuits of a vacuum tube power amplifier and analyzes their effects on the transmitter amplitude and group delay responses. Results of computer circuit analysis and actual measured data of a typical transmitter with two different topologies are compared. Design considerations for optimum transmitter performance to achieve the desired level of transparency to a wideband FM broadcast signal is also discussed including the effects of RF power amplifier tuning on the FM modulation performance. Scanned by John T. M. Lyles.
• Transmitter Cooling Systems: Design, Operation and Maintenance by Jeffrey H. Steinkamp, Broadcast Electronics. A thorough description of the cooling considerations in transmitter design and installation. Includes analysis of airflow, measured temperature rise, etc. Scanned by John T. M. Lyles.
• Spectrum Analysis - Amplitude & Frequency Modulation, local copy, HP Test & Measurement Application Note 150-1, 1996. Provides a nice explanation of why AM and FM generate sidebands, and how to use a spectrum analyzer to analyze AM and FM signals. 1.4M. Reproduced as authorized by Agilent Technologies. Contributed by Stanley Adams.
• Audio Signal Peak Energy Equalization - Patent 3,060,389 by L. R. Kahn, October 23, 1962. Basis for the Kahn SymmetraPeak
• Multiplex Frequency Modulation Transmitter, patent 2,773,125 by Edwin H. Armstrong, December 4, 1956.
• Circuitry for Multiplex Transmission of FM Stereo Signals with Pilot Signal, patent 3,122,610, by Antal Csicsatka, July 22, 1960. The DSBSC L-R with 19kHz pilot FM stereo method adopted in the U.S.

TV

• RCA Color Television System - Requirements for Compatible Color Television Systems - RCA Broadcast News, Jan/Feb 1954. Analysis of the RCA invented NTSC color television system.
• What Ever Happened to Channel 1 - A history of US television channel allocation. By John Reiser. See also Why don't US TV Sets have a Channel 1? by Bob Cooper.

Other

• Behind the Scenes at a Broadcasting Station By CARL DREHER, "Radio Broadcast", November 1923
• The Map Method for Synthesis of Combinational Logic Circuits, M. Karnaugh, November 1953. The origin of the famous Karnaugh Map method of simplifying logic.
• A New Standard Volume Indicator and Reference Level, H. A. Chinn (Columbia Broadcasting System), D. K. Gannett (Bell Telephone Laboratories, Inc.), R. M. Morris (National Broadcasting Company), 1939. This paper describes the development of the VU meter. 149.5kB Illustrations 91.8MB Scanned and contributed by Bill Ruck
• The Volume Unit, ABC Operations and Engineering, 1968. ABC general information on the Volume Unit. 2.3MB. Scanned and contributed by Bill Ruck
• Aspects of Audio Testing, ABC Operations and Engineering, 1966. Discusses VU, dBm, audio proof of performance, and discussing audio levels with telephone company personnel. 13.8MB. Scanned and contributed by Bill Ruck
• Personal Safety Considerations with Broadcast Transmitters, by Mukunda B. Shrestha, Broadcast Electronics. This paper discusses the various hazards which may be encountered, the safety requirements for transmitting equipment including standards and protective circuits, devices, and methods used in a typical broadcast transmitter to achieve the desired safety level. Scanned by John T. M. Lyles.
• Practical RFI Elimination Techniques For The Broadcast Engineer, by William L. Ammons, Broadcast Electronics. The paper deals with three major areas of Radio Frequency Interference: sources and modes of interference, techniques used in newly designed equipment to prevent RFI, and a discussion of the practical techniques a station engineer can use to minimize RFI in the station equipment. Scanned by John T. M. Lyles.
• Radio Antennas, Edmund Laport, 1952. Famous engineering text by the director of antenna and transmission line development at RCA Manufacturing. This text was downloaded from http://www.LuLu.com which offers various e-books. Submitted with request that all engineers find value in its' pages. Submitted by Stanley Adams
• Technical Notes on Multi-Channel Recording from Ampex - Discusses applications and technology behind multichannel recording, especially audio applications. Discusses signal to noise ratio verus track width, dealing with crosstalk, synchronous recording with playback of adjacent track. 1959. 13.6M. Contributed by Tim Hughes.

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