• Some Operational Considerations in Deploying Anti-Jam Communications

      Goldman, Herbert B.; Hughes Aircraft Company (International Foundation for Telemetering, 1977-10)
      Operational and deployment considerations are described to enhance the performance of jam resistant communications. The potential different ground propagation characteristics of spread spectrum and CW type waveforms are used to the advantage of the communication system. Emphasis is placed on the use of tactical relay to continuously optimize against the jammer. Tactics such as spoofing are described as a technique in confusing the intelligent jammer. The objective of this paper is to illustrate how anti-jam communications with nominal AJ performance improvement can effectively be employed in a ground environment. These include the brute force and the so-called intelligent or sophisticated jammer. For many years the utilization of anti-jam communications has been stifled in anticipation or the optimum solution against the optimum jammer. When evaluating a "one on one" scenario where the jammer is dedicated to jamming a specific link there is an unending subset of tradeoffs of optimum techniques to consider. However, when the jammer is trying to disrupt communications along a broad geographical axes. the techniques of jamming and communicating should be based on more general operating conditions. The ground communications environment in the presence of ground-based jamming presents the greatest opportunity for improving performance as a function of propagation anomalies and the use of relay. Airborne terminals within line of sight of the jammer have the most severe jamming environment. Ground based terminals generally will have an advantage of terrain against the ground based jammer. Those links that exhibit poor communications margin should always have the option of an alternate route in a jamming environment. The alternative to an alternate route is to provide excessive performance margins for worst case analysis. Unfortunately there is a significant cost factor associated with this latter approach. An important element of the scenario is the concept of position location. The use of position location and reporting equipment enables the apriori determination of appropriate links by different classes of users. As an example an aircraft can maneuver close to a ground terminal for communications to utilize the advantage of range ratio. This can be done in the worst case of a close Air Support Mission where the FO must provide voice or digital data to direct a strike at several mobile targets. At high altitudes the AC may be jammed but at low altitude the link may be viable. At low altitudes the aircraft A-G link will be constrained to a small geographic area and must therefore know which area to cover. The use of GPS can also be enhanced at low altitudes against the ground based jammer if acquisition of the GPS signal can be speeded up. The use of a digital matched filter (DMF) for CA code acquisition can provide this capability.
    • A Test System for a Miniature Neutron Detector

      Balls, Jerry D.; Bowers, John L.; The Bendix Corporation (International Foundation for Telemetering, 1977-10)
      A flexible automated test system for calibrating and testing a miniature neutron detector, used in telemetry systems, is described. The test system is cost effective, easily calibrated and maintained, and was available for use 6 months after design initiation.
    • NASA Standard Communications and Data Handling Subsystem

      Robinson, Daniel L. (International Foundation for Telemetering, 1977-10)
      At the 1975 International Telemetering Conference Charles F. Trevathan discussed the Multimission Modular Spacecraft (MMS) in general and the Communications and Data Handling (C&DH) subsystem in particular. The National Aeronautics and Space Administration's Goddard Space Flight Center (NASA GSFC) Is managing the MMS program and is integrating the first spacecraft, the Solar Maximum Mission, in-house. Contracts have been let for the Modular Power Subsystem (MPS), Attitude Control Subsystem (ACS) and the Communications and Data Handling (C&DH) Subsystem. The C&DH subsystem provides the command and telemetry link between the spacecraft and the terrestrial system; distributes commands to and collects telemetry from all spacecraft systems via a duplex serial multiplex data bus and Remote Interface Units (RIU's); and contains on board computation capability. The C&DH is a single 4 x 4 x 1- 1/2 foot module. The staffed module weighs 270 pounds including 60 pounds of mission unique equipment. The future for this kind of versatile hardware is exceptionally bright as it is cost effective and its modular structure permits repair, refurbishment and even modification/dating in space.
    • ARIA - An Inside Look

      Gast, Robert H., Jr.; Wright-Patterson AFB (International Foundation for Telemetering, 1977-10)
      The Advanced Range Instrumentation Aircraft (ARIA) is a mobile telemetry platform originally designed in the mid 1960s to meet the challenging voice and telemetry support requirements of the NASA Apollo Program. Since its inception, the telemetry instrumentation has been continually updated and improved. Each telemetry subsystem on the aircraft, Antenna, RF, Communications, Recording/Timing, and Data Separation is examined to provide an overview of the present capabilities. Additionally, signal processing methods employed for the realtime retransmission of analog and digital telemetry data are examined including the use of a minicomputer for digital signal processing.
    • Characterization of Tape Recorder Flutter in an Airborne Environment

      Rieger, James L.; Naval Weapons Center (International Foundation for Telemetering, 1977-10)
      While many methods are known for measurement of tape recorder flutter, most are intended for a laboratory environment, or at worst for situations where environment is under positive control. When the tape recorder is placed in a dynamic environment which is the source of the data to be recorded, tape flutter has a significant effect on the data accuracy. This paper describes some of the consequences of such flutter, and a method for separating the effects of flutter in the recording process from those encountered in playback; such information is required for the characterization of airborne tape recorders and for validation of data obtained.
    • JTIDS Modular Design to Use SAW Devices

      Grasse, Charles L.; Teledyne MEC (International Foundation for Telemetering, 1977-10)
      The Joint Tactical Information Distribution System (JTIDS) concept is designed to integrate the military's needs for communication, navigation and identification equipments into a cost-effective avionic suite. A key element to be used in achieving these goals is the surface acoustic wave (SAW) bandpass filter...in the form of a bandwidth selectable module. In order to satisfy the JTIDS requirements of today, as well as the Tactical Information Exchange Systems (TIES) of the future, it is necessary to utilize state-of-the-art SAW resonator/filter designs ... in conjunction with more conventional SAW bandpass filter technology. It is this approach that will make possible the quality performance required in a small, low cost module.
    • Encoding of Telemetry Data in a Standard Video Channel

      Rieger, James L.; Naval Weapons Center (International Foundation for Telemetering, 1977-10)
      Various methods for compressing of a television image to fit a channel of reduced bandwidth are available; most are difficult and/or expensive to use, and many degrade the resulting picture appreciably. This paper describes an alternative method of placing the signals which accompany the picture within the passband of a picture, and separating them again at the receiving end with minimum crosstalk and picture degradation.
    • Comparison of SAW, CTD and Conventional Digital Devices

      O'Clock, G. D., Jr.; Rockwell International (International Foundation for Telemetering, 1977-10)
      Two solid state technologies, which help to make certain types of signal processors, bandpass filters and matched filters more realizable and practical, will be evaluated and compared in this paper. Both of the technologies of interest have been developing over the past nine years. Both approaches can provide design simplicity, small size and low cost potential on a volume production basis.
    • MSK Modulation for Multiple Access

      Magill, E. G.; Fairchild Camera and Instrument Corporation (International Foundation for Telemetering, 1977-10)
      Minimum Shift Key (MSK) is known to possess desirable qualities, such as low spectral sidelobes and dual channels quadrature in both phase and sampling time. It is also a robust signal, tolerant to considerable amplitude limiting and spectral filtering. MSK modulation of Pseudo Noise (PN) sequences can be used to effect a communication network with multiple access, which can be of either random or assigned synchronism. Such a network exhibits resistance to jamming by external signals in the form of processing gain. This approach leads to multiple access terminal designs which are coherent, with a single RF front end which is not phase locked. A particularly effective implementation outlined in this paper utilizes a Charge Coupled Device (CCD) filter matched to the PN sequence as the basic correlating device for multiple access.
    • A Practical Look At Antenna And Propagation Requirements in Biotelemetry Systems For Fresh Water Fish

      Lindsay, J. E.; Long, F. M.; Weeks, R. W.; University of Wyoming (International Foundation for Telemetering, 1977-10)
      Propagation from a transmitter/antenna implanted in a fresh water fish is discussed. The choice of operating frequency based upon fish size, antenna efficiency and refraction effects is presented. The implanted linear antenna is placed laterally along the fish. It is shown that for parallel polarization (E in the plane of incidence) the wave, in air, has polarization dependent upon the elevation angle of the receiving antenna. For perpendicular polarization the polarization of the wave is always horizontal. Hence the polarization of the signal in the air depends upon the fishes position in the water. This leads to the conclusion that ground based receiving antennas should be circularly polarized so that either case can be handled. For air-borne tracking, the major cone of reception places the aircraft at higher elevation angles and hence requires a horizontally polarized antenna. Since the fish can be at various azimuthal angles, a circularly polarized antenna placed beneath the aircraft is dictated. The paper concludes with a discussion of an actual operating system as used by the U.S. Fish and Wildlife Service on the Truckee River.
    • A Frequency Modulated S-Band Telemetry Transmitter

      Homa, M. L.; Ward, J. H., Jr.; E-Systems (International Foundation for Telemetering, 1977-10)
      The need to efficiently collect data from remote locations has resulted in the widespread use of radio frequency telemetry. This paper addresses the requirements, considerations, and implementation of such a system. Since many components of a telemetry link are subjected to harsh operating environments, considerations of system constraints imposed on the transmitter by these conditions will be presented. Several design approaches of an S-Band frequency modulated telemetry transmitter will be offered, and tradeoffs associated with each discussed. Having selected the most desirable transmitter design approach a pictorial display of the hardware used to fulfill the requirements will be presented along with measured performance data. The key circuits discussed will be an S-Band VCO, parametric divider, buffer/power amplifier, and stabilizer/modulator. The RF circuits employ microwave integrated circuit construction while the stabilizer/modulator utilizes thin and thick film hybrid technology. Extensive use was made of computer analysis resulting in uniformly producible circuits that provide good correlation between measured and specified performance. This helped to produce a 25% reduction in production cost over the previous discrete component design of 1969 vintage. Basic circuit design lends itself well to special mechanical configurations, as well as flexibility in modulation formats and RF power output levels. By using the computer aided design approach, five percent RF bandwidths were realized which would enable the transmitter to be frequency agile for secure or multivehicle telemetry.
    • EDP Tape - Performance and Reliability - Past, Present and Future

      Fiori, J. J.; General Services Administration (International Foundation for Telemetering, 1977-10)
      This report was prepared by the Electronics Division, Federal Supply Service of the General Services Administration and is intended to share with all interested parties, the information and experiences with EDP Computer Tape gathered by the GSA since 1966, when it assumed the responsibility to support procurement of these items for all Federal agencies. It is hoped that the information contained herein will be of benefit to the tape-using community and will lead to a better understanding of the Government's role in providing high quality computer tape to meet current and future data storage applications. The General Services Administration's active involvement in the program to supply high quality computer tape to Government agencies was initiated through the development of Interim Federal Specification W-T-0051. The specification was based upon technical requirements received from the tape-using community and inputs supplied by the tape industry. GSA Laboratory facilities are utilized for product qualification testing, specification development testing and quality assurance testing. It is from all of these sources that the data presented herein was gathered. To establish some kind of perspective, it should be noted that these results are representative of the over 25,000 reels of computer tape sampled, tested and evaluated annually by GSA in support of annual procurement volumes of approximately 1 million reels. In addition to presenting quantitative data showing how tape quality levels have increased over the past four years, the report also addresses past problems and recent improvements, and further attempts to identify those remaining areas in which the tape industry must concentrate its future developments.
    • New Types of Flush-Mounted Telemetry Antennas

      Sindoris, Arthur R.; Jones, Howard S., Jr.; Reggia, Frank; Department of Army (International Foundation for Telemetering, 1977-10)
      Over the past few years new and unique types of cavity-backed, slot antennas have been developed that mount flush to the surface of a missile. These antennas have been designed and built to operate in the 300 MHz to 3 GHz frequency range and to produce low-gain (typically isotropic) wide-angle coverage with moderate radiation efficiency. As well as insuring good electrical performance, the basic design employs a copper-clad, dielectric-loaded cavity into which the radiating slot is machined or etched. This construction technique provides four important advantages: (1) The almost arbitrary shape or form factor of the cavity allows flush mounting to the surface of the missile or sandwiching between internal components with only the radiating slot exposed to the exterior of the missile. (2) Fabrication is simple. (3) Cost is low. (4) Mechanical strength is high. The cavity backing the slot is filled with a moderately high, dielectric constant material (such as a silicone, Teflon, or epoxy fiberglass) with a relative permittivity in the 2.5 to 4.5 range to decrease the size of the cavity and to provide mechanical strength to the antenna. The RF connection to the cavity is made by an inductive post and a coaxial connector. A 50 ohm input impedance is obtained over frequency bandwidths of 3 to 10 percent. By connecting two or more of these slot antennas together in a prescribed phase and amplitude relation, the direction of the radiation pattern can be controlled. Sidelooking or forward-looking patterns are possible by simple changes in feed network cable connections. The easy tunability of one of these new types of antennas allows application over greater than a 2:1 frequency range without any change in antenna dimensions.
    • Telemetry Antennas for Deep Space Probes

      Brejcha, Albert G.; Smith, Charles A.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1977-10)
      The requirement for real time imaging telemetry and the continued increase in science payloads on deep space missions have played a major role in the evolution of deep space probe telemetry antennas. This paper describes the high data rate telemetry antennas that were flown on the Mariner Mars 1969 and 1971, the Mariner Venus Mercury 1973, the Viking 1975 and the Voyager spacecrafts. Performance parameters are reviewed and general design concepts are described. The Mariner Mars 1969 and 1971 antennas were single frequency (S-band), one meter diameter antennas. The Mariner Venus Mercury 1973, Viking 1975 and Voyager antennas were dual frequency (S and X-band), with diameters of 1.4 meters, 1.5 meters and 3.7 meters respectively.
    • VHF Adaptive Array Test Results

      Zeger, Andrew E.; Burgess, Lawrence R.; General Atronics Corp. (International Foundation for Telemetering, 1977-10)
      A four-element Anti-Jam Antenna Array (AJAA) system has been built to provide protection for U.S. Marine Corps inter-command post communications in the 30-76 MHz band. A unique and important feature of the AJAA system is its ability to spatially null jammers down to a level below that of the desired signal. This capability and the prevention of accidental cancellation of the desired signal is achieved by using the desired signal's direction-of-arrival (DOA) in a prebeamformer located ahead of the adaptive beamformer. A positive S/J at the array output is required to prevent capture by a co-channel interference in standard FM field radios. Antenna range tests were performed on the AJAA system using AN/PRC-77 radios as far-field signal and jamming sources. Results of these tests show that the AJAA provides an intelligible FM voice signal at its output while simultaneously suppressing three jammers.
    • Best Source Selector System

      Alday, J. R.; Fleet Analysis Center (International Foundation for Telemetering, 1977-10)
      This system was developed in order to fulfill a need existing at the Fleet Analysis Center (FLTAC) Field Station-Caribbean, Telemetry Site at Roosevelt Roads, Puerto Rico. At the Field Station there exists four 16-foot diameter, two 8-foot diameter missile telemetry tracking systems plus a four frequency downlink Airborne Data Link (ADL) aircraft. With associated receivers, total number of video sources can be on the order of forty. Although all sources are recorded on magnetic tape and can be played back, only one or two sources can be displayed on high speed oscillographs simultaneously in "real time." The Best Source Selector System (BSSS) was developed in order to display, in real time, a continuous composite missile telemetry record which may consist of several individual sources. This System has been used continuously for the past three years for all missile telemetry operations at the Atlantic Fleet Weapons Training Facility (AFWTF), Puerto Rico. It has saved many man-hours of labor, searching tapes for bits and pieces of data and consequently, preliminary flight analysis and reporting to firing units (QUICKREPS) have been speeded up many fold.
    • Approximate Design Formulae and Procedures for Designing Hybrid Telemetry Systems Using an FM Carrier

      Lantz, Norman F.; Nichols, Myron H.; The Aerospace Corporation (International Foundation for Telemetering, 1977-10)
      Approximate engineering design formulae are presented. These are based on Rice's model of pop plus fluctuation noise in FM receivers. Several design examples are given. One hybrid system contains a baseband acoustic signal plus a PCM/FM subcarrier and another system contains a baseband PCM signal plus two PCM/FM subcarriers. Depending on carrier modulation parameters, the design formulae show that either pop noise or fluctuation noise in the carrier discriminator output may predominate in determining the bit error probability in the baseband and/or subcarrier services. Examples of each are given. The hybrid systems mentioned above were simulated in the laboratory. Test results are presented and show satisfactory agreement with the design formulae.
    • Detection of Scattered Optical Fields with Focal Plane Ring Detectors

      Vilnrotter, Victor A.; Hughes Aircraft Company (International Foundation for Telemetering, 1977-10)
      It is demonstrated that when communicating through scattering channels order-ofmagnitude improvement in system performance is possible by employing focal-plane processing techniques to recover some of the scattered radiation. Maximum a-posteriori and suboptimal system structures are derived and their performance evaluated. System sensitivity to the errors in the optimal weighting functions is discussed.
    • ECM/ECCM Effects on Voice Transmissions

      Buskirk, Ronald L.; Nossen, Edward J.; Government Communications Systems (International Foundation for Telemetering, 1977-10)
      An evaluation methodology for conventional and ECCM voice communications is presented, wherein intelligibility of the received message rather than error rate or signal-to-noise ratio is the quantity measured. This allows the engineer to include the psychoacoustic phenomena of a human listener in his system design considerations. Analyses have been performed which allow transformation of speech articulation test results into data more meaningful to the communications engineer. Since message intelligibility is established after baseband reconstruction of the voice signal, this method is universally applicable to most voice transmissions. It is insensitive to the nature of the medium, modulation, and interference sources. Examples are presented showing applications of these guidelines to the design of frequency hopping radios. Tests run on a simulator confirm the analyses. A sample tape is available to demonstrate some of the effects.
    • Understanding & Specifying Hi-Density Digital Recording Systems

      Schulze, Glen H.; Bell & Howell (International Foundation for Telemetering, 1977-10)
      Rapid advancement of hi-density digital recording technology has left most user organizations in a confused and bewildered state with respect to understanding and, more importantly, specifying hi-density recording systems. Users attempting to acquire advanced hi-density hardware either without procurement specifications or with incomplete or shallow specifications will probably gain the needed experience too late, after an unusable system has been delivered. Several prominent user facilities have recently bought and accepted hi-density recording hardware and immediately been forced to retire the equipment from use to avoid disastrous embarrassment. Other users have had to redesign accepted equipment before it could be used. One user who blindly accepted a proposal to convert several newly ordered analog recorders to a digital format had to remove and dispose of the digital electronics after delivery and revert back to analog methods. The ability to professionally specify and technically monitor a hi-density recording system contract can only be based upon a thorough understanding of the high density digital coding, recording, reproducing and decoding process. The purpose of this paper is to identify and discuss the more important elements of this emerging technology for users who suddenly find themselves needing this capability.