• New Concepts for Telemetry Converters

      Friend, Larry; Motorola, Inc. (International Foundation for Telemetering, 1966-10)
      Future requirements to convert present VHF telemetry receivers to L and S-bands can be satisfied by relatively simple solid state microwave converters. Use of the recently developed Schottky barrier diodes in balanced mixers along with high frequency field effect transistors in the intermediate frequency VHF preamplifiers, show considerable promise of providing low system noise figure (e.g. 5.5 dB) and low intermodulation distortion. These broadband converters have the potential advantages of minimum cost, size, weight, and power consumption, thereby providing a convenient and practical means for converting existing telemetry systems to the new frequency bands. Design considerations and predicted performance characteristics are presented for solid state converters of this type.
    • Application of Walsh Functions to Data Acquisition Systems

      Morton, Walter (International Foundation for Telemetering, 1966-10)
      The Walsh functions are considered with respect to the following system functions: 1. Concise signal representation. 2. Arithmetic operations. 3. Convolution and filtering. 4. Transfer function analysis. 5. Special measurements and functions: 5.1 Phase. 5.2 Digitally controlled function generator (DCFG). 5.3 Power density spectrum. 5.4 Correlation functions. The foregoing operations are required of equipment in the following areas of application: 1. Seismic data processing. 2. Hybrid data systems and simulation studies. 3. Special purpose Instrumentation.
    • Error Detection and error Correction Under the Conditions of Quarternary Decision Logic Techniques

      Brothman, A.; Yanis, C.; Halpern, S. J.; Miller, A. H.; Sangamo Electric Company (International Foundation for Telemetering, 1966-10)
      The hardware and theory of a multi-threshold bit decision technique called Quarternary Decision Logic are described. Quartenary Bit Decision Logic results in two simultaneous decisions on each received bit of a binary digital transmission: (1) a binary status decision; and, (2) a reliability decision which reflects on the presence/absence of multilation in the bit. Both decisions are based on a Shannon Integration of the received information over the whole bit interval. The ability to assess bit mutilation is then used to develop adjustable security-enforcing restraints on error correction and the receiving process itself. These restraints are developed by a Word Security Logic which keeps a "mutilation count" on each received word, The "mutilation count" per word results in a "Correction Permit/Inhibit" and a "Receiving Permit/Inhibit" output on each word. The "Correction Permit/ Inhibit" output bars error correction when the risk of a spurious correction is high. The "Receiving Permit/Inhibit” output blocks receiving when the risk of a direct evasion of security is high. The improvement in bit decision security and the improvements in security against spurious correction and direct evasions of Error detection are evaluated quantitatively in comparison to conventional single-threshold techniques, These improvements enable secure operation with lower redundancy coding systems because of the information gain which Quarternary Decision Logic provides. The possible contributions of Quarternary Decision Logic to self-adaptive data transmission systems and to automatic line equalization are explored in the section entitled "Conclusions".
    • RF Intermodulation Characteristics of VHF Telemetry Preamplifiers and Receivers

      Jeske, Harold O.; Sandia Corporation (International Foundation for Telemetering, 1966-10)
      Tests have been conducted on ten preamps and six receivers to quantitatively determine their linear operating range. The range of linear operation was determined by the measurement of, or the effects of, intermodulation (IM) products that were produced by the simultaneous application of two input signals. Measurements were made at a frequency equal to twice the frequency of one signal source minus the frequency of the other signal source. Tests of the ten preamps, which included eight solid state units, indicated that their dynamic range varies from approximately 46 to 70 db. Since the IM products of interest vary as the cube of the input signal, the output IM products may vary over a 72 db range, between the preamps tested, for a given input condition. It was found, under the best conditions with some receivers, that their proper operation was prevented by the presence of two signals that were less than 30 db larger than the desired signal. The two interfering signals were located well outside the rated - 60 db bandwidth of the receiver. The results of the tests should provide receiving system designers and operators with a better insight into the problem of RF intermodulation interference. Since no known military interference specifications consider intermodulation as investigated, it is believed that some standard test procedures should be developed by the telemetering community for preamp and receiver testing.
    • Polarization-Diversity Telemetry Receivers

      McCann, R. P.; Jones, R. D.; Sandia Corporation (International Foundation for Telemetering, 1966-10)
      Studies at the Langley Research Center of the National Aeronautics and Space Administration have shown that certain physical properties of extraterrestrial surfaces can be determined by analysis of impact-acceleration, time-history signatures obtained by instrumented projectiles (penetrometers). This paper considers the theory and design of a polarization-diversity receiver developed to receive and combine FM/FM penetrometer telemetry data. The signals are radiated by a set of orthogonal magnetic dipoles fed in time quadrature to obtain an omnidirectional radiation pattern similar to the pattern from a conventional turnstile. A special polarization-diversity receiving system is required to reduce the effects of fading of the RF carrier resulting from random changes in the orientation of the radiating antenna system. Various combining techniques are evaluated. Finally, a maximal-ratio, postdetection, dual-channel receiver with dual conversion and subcarrier discrimination developed specifically for the application is described.
    • Reconstructing a Serial Pulse Train from Parallel Data Recorded on Magnetic Tape

      Hadady, R. E.; Kinelogic Corporation (International Foundation for Telemetering, 1966-10)
      On-board data stores in deep-space probes, spacecraft, satellites, and aircraft, frequently require the extensive bit storage capability of a magnetic tape recorder. For compatibility with other systems, it is necessary in some cases to be able to reproduce the data in serial form at a synchronous rate. To take maximum advantage of the storage capability of magnetic tape, however, it is desirable in many instances to record the data in a parallel format; i.e., the technique used in magnetic tape recorders used with ground based computers. Reconstructing a serial pulse train with a synchronous bit rate from parallel data recorded on magnetic tape involves some problems which are peculiar to magnetic tape recording equipment. Variations in tape speed (flutter), dynamic skew (wobble) of tape as it passes over the record and playback heads and static skew of the data on the tape resulting from head gap scatter and mean gap azmuth alignment results in nonsynchronous data being generated during playback. To provide synchronous data output, it is therefore necessary to provide a buffer between the output of the magnetic tape recorder and the system accepting the data. Recorder characteristics are examined with respect to their effect on the degree of non-synchronism. Furthermore, the size and complexity of buffers necessary to provide synchronous output data is considered.
    • Predetection Diversity Combiner

      Casson, William Holton; Defense Electronics, Inc. (International Foundation for Telemetering, 1966-10)
      Pre-detection diversity combining provides a number of advantages in telemetry data reception, particularly when used in conjunction with pre-detection recording equipment. These advantages include optimal ratio signal combining before pre-detection recording, pre-detection signal-to-noise ratio and threshold improvement, higher improvement in demodulated signal-to-noise ratio as compared with postdetection combining, and a number of operational simplifications, which are further enhanced when the combiner is used with dual channel receivers. Laboratory tests verify predicted performance. Additional quantitative field data is needed, but preliminary results indicate excellent performance, and no problems in maintaining phase lock have been experienced.
    • An Experimental Investigation of the Capture Performance of FM Receivers

      Castellano, A. J., Jr.; Data-Control Systems, Inc. (International Foundation for Telemetering, 1966-10)
      This paper reports on the investigation of the effect of telemetry receivers capture ratio on overall system accuracy. Receivers with normal and improved capture ratio were compared to evaluate the methods used to measure capture ratio, determine the effect of I-F filter characteristics on capture ratio, and establish the penalty of bandwidth and distortion results including waveforms, photographs and spectral diagrams for various values of co-channel interference.
    • International Telemetering Conference Proceedings, Volume 02 (1966)

      International Foundation for Telemetering, 1966-10
    • Channel Noise - A Limiting Factor on the Performance of a Class of Adaptive Techniques

      Raga, Gerald L.; Electro-Mechanical Research Inc. (International Foundation for Telemetering, 1966-10)
      The effects of channel noise on a class of adaptive sampling techniques based on the concept of removal of redundant data samples were investigated. Assuming a system of fixed bandwidth and fixed transmitter power, the channel noise forces the adaptive system to operate at a lower bit error probability than the equivalent PGM system since in the adaptive system each transmitted bit represents more information. This limitation was partially overcome by adding error criterion of unequal weighting to the data which enabled the system to operate at essentially the same bit error probability as the PCM system with a net coding efficiency greater than the coding efficiency of the error-correction code. Experimental results from subjective tests, and the RMS error demonstrate that a new error criterion must be developed for the class of adaptive techniques.
    • PCM Transmission with Minimum Mean-Square Error

      Clark, G. C.; Totty, R. E.; Radiation Incorporated (International Foundation for Telemetering, 1966-10)
      One source of error in PCM transmission of analog waveform is the bit errors made in the binary sequences representing a particular level. Using a mean-square error criterion, the contribution of this (channel) error to the overall reconstruction error is examined. In particular, general simplified error expressions are derived for arbitrary sequence assignments including error correcting coding. Results are given for the power gain resulting from use of several error correcting codes. The criterion used here is mean-square error (rather than word probability of error) and the coded sequence is constrained to occupy the same time interval as the uncoiled sequence.
    • Desired Telemetry System Characteristics for Shock, Vibration, and Acoustic Measurements

      Himielblau, Harry; Subcommittee G-5.9 on Telemetry Requirements; SAE Committee G-5 on Aerospace Shock & Vibration (International Foundation for Telemetering, 1966-10)
      For over a decade structural dynamicists and acousticians have registered general dissatisfaction concerning the limitations of telemetry systems, especially the insufficient number of channels and insufficient data bandwidths. To spell out the users' need for present and future telemetry, a representative group of dynamicists was organized under the SAE. Requirements for number of channels per flight, data bandwidths, minimum dynamic range (with stationary and transient data signals considered separately), certain accuracy, phase and other characteristics were established. The subcommittee is hopeful that this information will spur the telemetry community into developing and standardizing on new systems with superior characteristics.
    • Low Level F. E.T. PAM Multicoder

      Gregory, Terence R.; General Devices, Inc. (International Foundation for Telemetering, 1966-10)
      This paper describes a new all solid state airborne low level PAM multicoder that employs N-channel FET for all the analog switching functions of the system. The unit features a 72KHz true chopper amplifier that affords complete isolation between input and output. This unit is fully developed and went into production in June 1966 offering many advanced features to airborne telemetry system users. Each input channel presents a true differential analog switch into the low level D. C. amplifier. The operating characteristics such as C. M. R. (100 db) out to 1KHz, no D. C. drift or gain-change, and selectable pedestal levels add to ease of operation and flexibility. Heavy use of integrated circuits was also made including monolythics, hybrids and discrete elements. The gating logic, chopper amplifier front end, and carrier amplifier/synchronous demodulator each have a separate power supply winding thus providing excellent isolation for user applications. Mechanical construction employs plug in boards affording ease of manufacture and complete interchangeability of boards between units. The system is discussed as to unique features and techniques necessary to build the unit and satisfy stringent specifications.
    • A New Analog Magnetic Recording Technique

      Johnson, W. R.; Jorgensen, F.; Fairchild Winston Research (International Foundation for Telemetering, 1966-10)
      The magnetic recording process using ac bias is reviewed and applied in a discussion of recording heads. The difficulties in obtaining a sharp gradient are explained. A new magnetic recording head that overcomes the weaknesses of conventional heads is described and compared with the conventional ring core head. Performance data are listed and show improvement in frequency response, decrease in harmonic and intermodulation distortion, reduced electronics and higher reliability.
    • Magnetic Tape Recorder Spectral Purity

      Bradford, R. S.; 3M Company (International Foundation for Telemetering, 1966-10)
      The data recovery and reduction processes of various telemetering systems have clearly demonstrated the critical role of flutter and time errors in instrumentation recording and reproduction. One of the effects of these errors is that of "frequency smearing" of individual recorded/reproduced sine wave components. The advent of precision tape speed servo control has reduced these errors to a point where a detailed examination of the residual effect becomes both possible and profitable. The detailed measurements of the resultant spectrum of a recorded/reproduced sine wave component are described. These are quantitatively analyzed and interpreted in terms of the flutter and time error characteristics of the recording/reproduction system.
    • New Concept in High Reliability Tape Recorders for Spaceborne Data Storage

      Burdorf, D. L.; Kinelogic Corporation (International Foundation for Telemetering, 1966-10)
      The need for large bit capacity in on-board data storage for deep-space probes, spacecraft, satellites, and aircraft, has created a requirement for a tape recorder of ultra-high reliability. In an ideal recorder, the conventional capstan would be eliminated and the reels would be driven such that the linear velocity and the tension of the tape between reels would be constant from the beginning to the end of the reel. The heads would also be the only elements in contact with the tape. Reliability would be enhanced by driving the reels, rather than the tape, through a reduction in the number of moving parts. Reducing the number of elements in contact with the tape would also increase tape life. The Iso-Elastic Drive, closely approaches the ideal recorder drive system. The reels are driven by a seamless polyester belt which is in direct contact with the periphery of the tape reel. The belt is driven at constant linear velocity (resulting in low flutter) and in such a manner that it generates a constant tension in the tape connecting the two reels and passing across the heads. Constant tape tension in a high-reliability recorder is necessary in order to optimize 1) tape tracking and guidance, 2) effective bias level on the tape during direct-type recording, 3) playback level, 4) head wear, and 5) drop-outs. The Iso-Elastic Drive reduces the number of moving parts by approximately 30% as compared with conventional recorders. The tape drive has the additional desirable characteristic of operation equally well in either direction.
    • Magnetic Memory Techniques for High Accelerations

      McAlexander, J. C.; Cook, S. C.; Bell Telephone Laboratories; Sandia Corporation (International Foundation for Telemetering, 1966-10)
      A system to obtain and record impact data at accelerations of 3000 g’s has been designed around a 1024 word, 12 bits per word, piggyback twistor memory. Memory construction and potting techniques were developed to minimize the effect of large acceleration forces. The memory and system tests prove that the memory can withstand shock signatures beyond its original design requirements.
    • A User Controlled Test Data Computing System

      Fink, A. J.; Boeing Aerospace Group (International Foundation for Telemetering, 1966-10)
      Test data systems have not yet fully capitalized on the use of digital computers for the handling of test and test related data. Advancements in computing technology will make it possible to improve total efficiency of test information systems by coupling data sources to data users through remote terminals connected directly to large timesharing computing systems. The concepts which can be applied to effecting this coupling are described.
    • UHF Telemetry Systems Design for The Edwards High-Range

      Blakely, R. T.; Bosinoff, I.; Heenan, N. I.; The Mitre Corporation (International Foundation for Telemetering, 1966-10)
      A systems design analysis for the Edwards High-Range UHF telemetry receiving station network is described which takes into account reliability, availability, design adequacy, and initial and operating costs. Alternate High-Range configurations investigate the utility of sites using omnidirectional, sector, and steerable antenna systems in both the manned and unmanned modes of operation. In the analysis, reliability, availability, and design adequacy are combined as a measure of system effectiveness in a manner that permits the system design to be selected on the basis of maximum system effectiveness for a given total systems cost. Finally, an operational guideline is presented that permits the future programming of the range operation and expansion to be premised on probable losses incurred due to down-time.
    • A Scientific Lunar Payload Communications System

      Wilker, L. B.; Space-General Corporation (International Foundation for Telemetering, 1966-10)
      Based on the selection of scientific instruments suitable for application to the payload, conceptual designs were synthesized of payload packages, including the supporting subsystems. Parametric and/or conceptual design studies were conducted of such areas as communications. The primary communications link was to be payload to lunar survey probe communication facility carried with the Apollo vehicle, e.g., modified LEM. No burden was to be placed on the basic Apollo communication system. Payload-to-earth link was also to be considered as an alternate mode, particularly for the long duration instrument operation. The communications system described in this report is a natural outgrowth of the mission requirements and presents a realistic approach to a solution of the communications problems. As such, the system described could be readily instrumented, utilizing current state-of-the-art hardware and techniques.