• International Telemetering Conference Proceedings, Volume 06 (1970)

      Unknown author (International Foundation for Telemetering, 1970-10)
    • The Effects of Using a Finite Number of Bits and Approximate Division in a Data Compressor

      Bjorn, T., Jr.; Harshman Associates, Inc. (International Foundation for Telemetering, 1970-10)
      In the design of a data compressor one of the basic problems is error due to the use of a finite number of bits in calculating various parameters. This is error due to truncation (or round off) after a set number of bits to the right of the binary point. Another error that could be introduced to the system is that error caused by the use of an approximate divide instead of a full divide. It is the purpose of this study to find the effect of these two errors so that (1) a judgment may be made as to how many bits to the right of the binary point are necessary, and (2) find if a double shift approximate divide may be used instead of the slower full divide. The study is divided into three basic parts (1) the effect of truncation (or round off), (2) the effect of the double shift approximate divide, an (3) the combined effect of truncation (or round off) and the double shift approximate divide. Each one of these error-causing phenomenon has two variations; i.e., an error caused while compressing data and an additional error caused while reconstructing. The error during compression distorts the tolerance limits, and the error in reconstruction causes distortion of the reconstructed line segment. Each of the errors leads to an overall error in data magnitude over and above the normal allowable error of one tolerance level. For all of the analysis the maximum run length of the compressed data is assumed to be 128. A summary of the study is found in Table 6.
    • The Upper Bounds of the Confidence Intervals of Bit Error Probabilities Based on a Markov Chain Bit Error Model

      Mizuki, M.; Vandenberg Air Force Base (International Foundation for Telemetering, 1970-10)
      Confidence intervals for the bit error probability of an actual PCM telemetry data can be determined based on the analysis of received redundant bits. The procedure usually requires the assumption of independence of bit errors. However, bit errors may occur in clusters under various conditions of multipath, injection of nonthermal noise of long duration, and bit jitters. As a representation of bit errors in clusters, a Markov chain model is introduced. Some results on the confidence interval of bit error probability are obtained as functions of a Markovian parameter, which designates the degree of departure from the binomial model. The computations are quite laborious compared to the case of the binomial model. This paper gives step-by-step instructions for computing the probabilities that r error bits occur among mn received bits which can then be used for the derivation of the confidence interval.
    • Format and Address Equation Generation by Computer

      Leighou, R. O.; Hill, K. H.; Martin Marietta Corporation (International Foundation for Telemetering, 1970-10)
      Addressable remote multiplexed time division telemetry systems are being used more and more. Most of these systems operate with serial addresses generated by a central unit where each data source has a unique address. Thus the address sequence determines the particular format. In one type of system, the address sequence is determined by transfer logic between a counter and an address shift register. It takes several man-weeks of effort to develop a format and the logic equations to implement the address sequence for that format. To avoid this effort, an algorithm and computer program that generates the formats and the logic equations has been developed and is described. The program data inputs are: the basic format configuration of addresses (channels or data sources) per frame and the frames per master frame; and the number and types of channels at each samples per master frame (S/MF) rate. The program outputs are: address assignments by program ID, telemetry formats sequences with program ID, and the set equations for the address output shift register. Several checks are made during the program and if program restrictions are violated or format generation is impossible, error messages are printed and the program may be halted.
    • Machine-to-Machine Compatability in Wideband recording

      Levy, Avner; Ampex Corporation (International Foundation for Telemetering, 1970-10)
    • Manned Space Flight Network Unified S-Bond System 1970

      Spearing, R. E.; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
    • Appendix A: Telemetering Standards Coordination Committee Report

      Gardenhire, Lawrence W. (International Foundation for Telemetering, 1970-10)
    • The Lunar Communications Relay Unit System Design

      Trachtenberg, B.; RCA Corporation (International Foundation for Telemetering, 1970-10)
      Lunar Surface Exploration by Early Apollo Astronauts was limited by the range capabilities and configuration of the surface communications. To permit greater scientific yield from manned lunar exploration, it was necessary to provide improvements in crew mobility plus communications compatible with extended extravehicular activity. Expansion of EVA and video communications capability was constrained by the requirement of interfacing with existing earth and lunar surface facilities, vehicle payload requirements, and crew operational considerations. Various trade-off s were conducted to permit rapid development of a feasible communication's system which are described herein. The revision of the EVA mission profile necessitated establishment of new signal design parameters compatible with mobile and fixed site relay configurations. The design approach selected required strict discipline to enable integration of the electrical, mechanical, thermal and human factor fields. The resultant design of the Lunar Communications Relay Unit is a portable communications package to provide relay-to-earth of voice, data and color television from lunar surface locations far beyond the LM landing site and relay of ground voice to the EVA crew.
    • Processing of NRZ PCM from 10 MB/Sec to 200 MB/Sec

      Gray, J. S.; Radiation Systems Division (International Foundation for Telemetering, 1970-10)
      The type of functions required to optimally process PCM plus noise are the same at low and high bit rates. At high bit rates there are severe constraints in synthesizing these functions due to limitations of present day devices and logic; and due to extrinsic effects of networks over broad baseband bandwidths. Techniques developed for signal conditioning, bit synchronization, group synchronization, and decommutation of NRZ PCM from 10 Mb/sec to 200 Mb/sec are presented. Multiple techniques were investigated in each area over the complete bit rate range of interest to ascertain performance versus complexity and cost effectiveness among different techniques at different bit rates.
    • Feedback in Data Transmission

      Ebert, P. M.; Bell Telephone Laboratories (International Foundation for Telemetering, 1970-10)
      A survey of the possible gains to be realized by the use of various feedback techniques is given. Noiseless information feedback is considered in detail, and a transmission system for this latter case is given and analyzed. This system is shown to achieve a transmission rate very close to the largest rate possible.
    • Data Tranmission Over Channels with Noisy Feedback

      Tong, S. Y.; Bell Laboratories (International Foundation for Telemetering, 1970-10)
      A low-cost error control technique is proposed for bulk data transmission with noisy feedback link. The scheme is ideally suited for tape-to-tape bulk data transmission as well as the store-and-forward type of data transmission system. By partition data into superblocks, the technique can be used for any feedback retransmission system. We also show that the scheme can be modified to correct synchronization errors and that noise in the feedback link can be made extremely unlikely to contribute to decoding errors.
    • VHF/UHF Antenna Calibration Using Radio Stars

      Taylor, Ralph E.; Stocklin, Frank J.; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      This paper describes a stellar calibration technique, using radio stars, that determines receiving system noise temperature, or antenna gain, at frequencies below 500 MHz. The overall system noise temperature is referenced to radio star flux densities known within several tenths of a decibel. An independent determination of antenna gain must be made before computing system noise temperature and several methods are suggested. The preferred method uses celestial and receiving system parameters to compute gain; whereas a less desirable method requires an accurately known output level from a standard signal generator. Field test data, obtained at 136 MHz and 400 MHz in the NASA space tracking and data acquisition network (STADAN), demonstrates that antenna gain and system noise temperature can be determined with an accuracy of 1 db. The radio stars Cassiopeia A and Cygnus A were used to calibrate 40-ft. diameter paraboloidal antennas, at 136 MHz and 400 MHz, and phase array antennas at 136 MHz. The radio star calibration technique, described herein, makes possible accurate station-to-station performance comparisons since a common farfield signal source is observed. This technique is also suitable for calibrating telemetry antennas operating in the IRIG 216-260 MHz frequency band.
    • Video Bandwidth, if Bandwidth and Peak Deviation in Notch Noise Testing

      Little, K. G.; Astro Communication Laboratory (International Foundation for Telemetering, 1970-10)
      This paper presents guidelines for conducting notch noise testing of telemetry transmitter-receiver systems. An understanding of the type of FM-FM modulation format which random white noise accurately simulates leads to certain convenient relations between spectral power density, video bandwidth, peak deviation and IF bandwidth. Notch noise measurements were made on video noise in a video limiter to determine the dynamic range required of a system which transmits random white noise faithfully. These measurements were of significant importance because they show that a great deal of excess IF bandwidth is required to transmit random noise spectra. Specifically, it was found that to achieve a 50 db notch noise measurement the system dynamic range may be as much as 10 times greater than the RMS value of the composite signals.
    • Notch Noise Loading Data on Baseband Tape Recording

      Heideman, W. R.; Nichols, M. H.; Aerospace Corporation (International Foundation for Telemetering, 1970-10)
      Notch power ratio tests were performed on a magnetic tape recorder/ reproducer, using direct recording in the baseband. For the equipment tested, it is concluded that the IRIG method of setting the record power level as that which produces 1% third harmonic on a single tone, does not necessarily result in an optimum record/reproduce cycle. It is concluded that the input and output levels should be set with reference to notch noise test data to optimize baseband tape recording performance for baseband recording of frequency division multiplexed systems. In order to interpret the notch noise data, it was necessary to assume two non-linear processes, one acting in conjunction with the record process and one in conjunction with the playback process.
    • Performance Evaluation Medthos for PCM Bit Synchronizer/Signal Conditioners

      Peavey, B.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      PCM Bit Synchronizer/Signal Conditioners (BSSC) possess 3 basic performance characteristics which directly affect the processing of PCM telemetry data. These characteristics are: bit error rate (BER), bit slippage rate (BSR), and bit sync acquisition (BSA). This paper describes proven methods to meaningfully, and accurately measure these characteristics with particular emphasis on BSR and BSA. These methods require relatively simple and inexpensive procedures and instrumentation, and could be used by manufacturers and users to evaluate and acceptance test BSSC. The basic principle employed in these methods is "fixed threshold frame synchronization" with a unique strategy. Thus, there is no requirement for bit delay between the reference and BSSC output data, and synchronization of the reference data in the comparator with the BSSC output data takes place automatically. Moreover, this approach to testing BSSC represents the actual situation in which the BSSC would be operating as part of the telemetry data system, and hence would provide a direct measure of system performance. In actual application, these methods proved to be very effective and accurate for input SNR of E(b) /N(0) > O dB, and slightly less accurate for E(b) /N(0) < O dB (data having more than 10% errors). In general, BSA and BSR measurement accuracies of 20-30 bits can be achieved. A detailed discussion of accuracy is presented in the paper. In addition, the BSR and BER measurement methods are applicable to assessing the performance of tape recorders (TR) as it affects the actual system performance, rather than just the peculiar TR characteristics of TBE (time base error), bit dropout, and wow and flutter.
    • Noiseless Linear Feedback and Analog Data Tranmission

      Butman, S.; California Institute of Technology (International Foundation for Telemetering, 1970-10)
      It is well known that noiseless linear feedback achieves channel capacity for the additive Gaussian channel. It has also been shown that it can be used to achieve the rate-distortion bound on the mean squared error for an arbitrary Gaussian source sent over the infinite bandwidth white Gaussian channel. However, it is shown here that noiseless linear feedback by itself does not suffice when the channel is bandlimited. It is shown that, out of the more than countable variety of Gaussian sources that ordinarily exist, only a countable subset can be transmitted via the bandlimited noiseless feedback link at the theoretical efficiency predicted by Shannon's rate-distortion bound. Thus, some nonlinear operations are necessary in almost all cases even with feedback.
    • A Burst-Trapping Code for Feedback Communication Systems

      Weinstein, S. B.; Bell Telephone Laboratories, Inc. (International Foundation for Telemetering, 1970-10)
      Many data communication channels are perturbed by "bursts" of noise separated by long intervals of comparatively low noise level. The block code described in this paper, a modification of the forward-acting scheme of S. Y. Tong, retransmits information which has been damaged by a noise burst in place of the parity-check digits of future blocks. The responsibility for error detection and correction is divided between the receiver and (via the feedback channel) the transmitter in such a way as to maximize the defense against both noise bursts and the occasional random errors between bursts. There is a fixed delay for decoding, in contrast to the variable buffering delay of ordinary retransmission-request systems. As a result, storage requirements are minimized and there is a constant throughput rate. The feedback channel can incorporate as much delay and be as noisy as the forward channel without significantly impairing performance. Simulation results are provided to illustrate the performance.
    • A Universal L-Band Telemeter for Use on Artillery Projectiles and Gun Launched Research Probes

      Richard, Victor W.; Hadowanetz, Wasco; Aberdeen Proving Ground; Picatinny Arsenal (International Foundation for Telemetering, 1970-10)
      A UHF (1520 MHz) telemetry system for use with artillery projectiles and gun launched research probes is described. The feasibility of a universal telemeter (UTM) is demonstrated which is based on the use of modular plug-in components available to meet a variety of instrumentation requirements, including ogive and rear mounting, thus, eliminating the need for the development of a special projectile telemetry unit for each application of in-flight projectile performance monitoring or gun probe experiment. The special, ruggedized components and techniques for pre-flight high acceleration testing are described. The components described include: broadband, omnidirectional antennas for ogive and base mounting in projectiles; a high gain, all polarization, fan beam receiving antenna; stabilized, high efficiency UHF transmitters; miniaturized voltage controlled oscillators; 8 and 16 channel commutators; button cell and g-activated reserve cell batteries; shock resistant, electrically compatible radome and encapsulating materials; modular assembly cases; and ogive and base mounted telemeter test projectiles. The physical and electrical characteristics of the components of the telemetry system are presented, along with laboratory and field performance data obtained from firing standard, 155 mm, spinning projectiles, including the reception of signals while the projectile is in the gun barrel.
    • Apollo Lunar Communications

      Sawyer, Ralph S.; NASA Manned Spacecraft Center (International Foundation for Telemetering, 1970-10)
      The Apollo unified S-band system was developed to handle ranging, telemetry, and voice data using one carrier. Television is transmitted in another mode with the same system. Frequent references are made to the unified S-band system in this report because other systems must work in conjunction with it; however, no description is provided because the S-band system is discussed thoroughly in numerous other reports. The astronauts must coordinate their activities on the lunar surface, and communications are required between them as well as between them and Mission Control Center. A VHF system that has performed excellently in providing voice and telemetry information for lunar-surface use is described in this report. Interest in television has progressed from casual to intense as the Apollo Program has matured; technology has evolved to provide color presentations using the same RF system that was once limited to black-and-white transmissions. The cameras that were developed for both black-and-white and color transmissions are described. Future lunar-surface operations will require traverses too long to be accomplished easily on foot. A system that permits long-range communications from a motorized vehicle on the lunar surface is described. Finally, brief descriptions of several communications-related lunar-environment experiments that have been proposed for the Apollo Program are discussed.
    • Quartz Crystals Units for High G Environments

      Bernstein, M.; U.S. Army Electronics Command (International Foundation for Telemetering, 1970-10)
      Quartz crystal units are commonly used to achieve frequency accuracy of the order of 100 parts per million or better. The usual crystal mechanical environments are quite benign compared with those encountered In high g telemetry, however, and the normal shock tests are only 100 g's. The preliminary, design of a ruggedized high frequency crystal unit is shown as well as test date on the behavior of these units when subjected to 15,000 g's of impact shock. A crystal resonator is quite fragile since at 20 MHz an AT resonator is only 3 thousandths of an inch in thickness. Higher frequency units appear to have a g limit only slightly in excess of 20,000 g's. At lower frequencies, the resonator is not the limiting element but the supports and bonds become unreliable. A trade-off must be made between a very stiff support, which will increase the acceptable g level, and the concomitant frequency instability due to changes in mechanical stress on the quartz resonator. These stress changes can be caused both by differential thermal expansion of the mount and quartz as well as by shock Induced effects.