• An Adaptive Airborne VHF/UHF Transmitter System

      Franke, E. B.; Trover, W. F.; Teledyne Telemetry Company (International Foundation for Telemetering, 1968-10)
      The impending 1970 change-over of telemetry RF links from VHF (215- 265 MHz) to UHF (1435-1545 and 2100-2200 MHz) requires a quantum jump in the state-of-the-art of solid-state transmitters. This problem is compounded by the fact that in certain instances, especially for spacecraft and special applications, there is still a need for transmitters at many different VHF and lower UHF frequencies between 136 MHz and 1 GHz. Therefore, the optimum RF product line is represented by a modular transmitter system composed of fundamental building blocks which will permit the assembly of transmitters capable of producing from 50 watts at 136 MHz to 1/2-watt at 5500 MHz with minimal variations in the over-all mechanical configuration. This adaptive transmitter system must also be able to provide optional features such as power-to-case ground isolation, modulation-to-power ground isolation, turn-on current limiting, either frequency of phase modulation remote turn-on capabilities, and internal telemetry functions of temperature, RF power, dc voltage. Additional design requirements for such a transmitter system are wideband frequency response and carrier deviation capabilities so that the transmitter may handle real-time video signal for use with television, radar and infra-red transmission systems. This paper describes the design alternatives and the conceptual approaches that were used in development of such an adaptive transmitter system. Performance data presented is typical of that achieved from L-band and S-band units.
    • Appendix A: Seventh Annual Report of the Telemetering Standards Coordination Committee

      Frost, Walter O. (International Foundation for Telemetering, 1968-10)
    • Bit Error Rates in the Presence of Untracked Time Base Fluctuation

      Roche, A. O.; Mallory, P.; General Dynamics; Dynatronics (International Foundation for Telemetering, 1968-10)
      This paper presents a simple four-step procedure for estimating the error probability of an NRZ PCM Synchronizer and Detector operating on an NRZ Bit Stream in the presence of a fluctuating data frequency source. The four steps are as follows. First, the bit error probability is calculated for Gaussian time base fluctuation as a function of the energy per bit to noise power density ratio. The second step is to model the synchronizer as an ordinary linear servo for small phase errors and a closed loop bandwidth, small compared to the bit rate, so that effect of the randomness of the data is averaged out. With the linear model, the time base error in tracking the input signal is calculated also utilizing this approximation as if there were no additive noise. The third step is to calculate the mean squared time base error due to the additive Gaussian noise alone. The fourth step is to combine the errors found in steps two and three as if they were independent and use the graphs found in Step 1 to determine the error rates. It is assumed that the total untracked time base fluctuation is Gaussian. The calculated error probabilities are compared with measured data. There appears to be good correspondence between the calculated and measured error probability.
    • Buoy Telemetry for Environment Prediction in Fisheries Research

      McAlister, W. Bruce; Bureau of Commercial Fisheries Biological Laboratory (International Foundation for Telemetering, 1968-10)
      A telemetering buoy has been developed for the Bureau of Commercial Fisheries to provide environmental information in support of salmon research. The buoys are designed to be free-drifting units; sensors are inductively coupled to a 200 m. single conductor cable beneath the buoy. Present sensors measure temperature, conductivity and depth. One buoy is equipped to participate in the IRLS satellite telemetry experiment. Present development includes equipment to have the buoys determine their position by use of the U.S. Navy Navigation Satellite System.
    • Cause and Effect of Time Base errors in Coherent Demoudlation of a Suppressed Carrier AM Multiplex

      Nichols, M. H.; Schmitt, F. J.; White Sands Missile Range; Lockheed Electronics Company (International Foundation for Telemetering, 1968-10)
      Two types of time base error, TBE, are discussed. One type results from variations in tape speed (flutter) and the other type is the result of additive noise. Measured data on TBE from a typical tape machine are included. Quantitative effects of TBE on coherent demodulation of DSB, SSB and quadrature DSB are discussed.
    • Communications Between Satellite and Ballons for the Eole Mission

      Bourdeau, J. P.; Debray, P.; Namy, X.; CNES (International Foundation for Telemetering, 1968-10)
    • Communications for the Apollo Applications Programs

      Fordyce, Samuel W.; NASA (International Foundation for Telemetering, 1968-10)
      The Apollo Applications Program will consist of a series of extended duration manned missions in low earth orbit. The initial missions are based upon equipment and techniques proved in previous space flight programs. This is especially true of the communications systems which rely heavily on the Gemini, Saturn, and Apollo communications hardware operating with the Manned Space Flight Network. Following AAP missions may include new spacecraft developments involving television, teleprinters, satellite relays and spacecraft data management systems. These developments are described briefly, but many of them are concepts in early development stages, and it is difficult to specify the configurations that will be flown.
    • Compatibility Requirements and Considerations of Range Telemetry Tape

      Schulze, G. H.; Pan American World Airways, Inc. (International Foundation for Telemetering, 1968-10)
      Range Telemetry Tape crossplay operations may be arranged into four major classes each with unique compatibility considerations: a. Between like recorders at the same Range. b. Between unlike recorders at the same Range. c. Between unlike recorders at different Ranges. d. Between unlike recorders at Range User facilities and the Ranges. Like model recorders at the same Range are more likely compatible and capable of optimum tape crossplay than any other combination. Sometimes this very fact produces an atmosphere of complacency which can invite problems. The assumption that the recorder manufacturer has properly controlled his production for optimum crossplay or for complete conformance to IRIG1 is naive and should not be a substitute for compatibility testing at the using Range facility. With field use and equipment aging, compatibility can be gradually lost without becoming detected. Adjustment procedures at one' site may not be identical to procedures at other sites and perfectly compatible equipments can unknowingly become incompatible. The absence of adequate compatibility testing is the major cause of difficulty with this class of crossplay. Crossplay between unlike model recorders at the same Range poses unique problems but these can be controlled providing the unlike recorders have individually been strictly specified and tested to conform to IRIG Standards. Compatibility testing by the using Range is a definite requirement as manufactures may differ in their interpretation of the IRIG Document or may differ in the extent to which they conform. No manufacturer appears to be knowledgeable regarding crossplay between competitive recorders, and some appear to be just as uncertain about compatibility between complimenting recorders from their own product line. Crossplay between unlike recorders at different Ranges is being accomplished but many factors stand in the way of automatic success for this type of venture. When different equipments, different tape types, different operational procedures, and different procurement specifications all combine, the compatibility of the whole system is strained. The possibility of different tape types specified by competing equipment manufacturers should produce cautious awareness by the user and compatibility testing with both tapes should be conducted. The question "Which Range is responsible for the incompatibility?" can be difficult to answer. Currently, no central agency exercises control over Range-to-Range crossplay compatibility, and each Range conforms to IRIG Standards on an individual basis. Crossplay between unlike reproducers at Range User facilities and Range copy recorders is probably the most severe test of compatibility that exists. In this type of crossplay IRIG Standards may not have been invoked by the Range User, different bandwidth classes of systems may be involved and the fact that the User, and the Range may be virtually strangers all promote an environment unconducive to compatibility. Anything that can possibly go awry usually does. The major responsibility must lie with the Range who supplies the original or copy tapes to the Users. Ideally, the copy tapes should all be generated identically regardless of individual recipient requirements, and the IRIG Standards should be religiously followed.
    • Cracked Solder Joint Mechanism in Discrene Component Assemblies

      Estes, H. P.; Theobald, P. E. (International Foundation for Telemetering, 1968-10)
      Solder joint cracking has occurred in assemblies where discrete part subassemblies are fabricated on Printed Circuit Boards and conformal coating is applied to the sub-assembly. The objective of the investigation were to determine the extent and seriousness of the problem, to determine the cracking mechanism, and to provide engineering and process information to eliminate the problem. The analysis and test results indicate that many factors influence the strength of a solder joint and the ultimate crack that develops. Contamination by gold products and other foreign materials can significantly affect solder characteristics. Aging and temperatures experienced in the normal operating range of certain equipment adversely affects the strength of the solder materials. Conformal coating between the discrete part and the Printed Circuit Board is a major contributor to the cracking mechanism. Transistor assemblies using a Spacer under the TO-5 enclosure with Kovar Lead Material and completely covered with conformal coating have a high incidence of cracked solder joints. This condition is caused by the mis-match of coefficients of expansion between the Kovar Lead and the conformal coating.
    • A Data Recording System for Deep Sea Logging

      Ben-Yaakov, S.; UCLA (International Foundation for Telemetering, 1968-10)
      A data recording-reproducing system has been developed in conjunction with an oceanographic in situ multi-sensor probe for measuring chemical properties. The recording unit is built around a deck of a single channel, entertainment-type miniature magnetic tape recorder. The tape speed was reduced to 0.125 ips by slightly modifying the original speed control, which results in four hours' continuous recording. The recording unit incorporates a frequency counter to convert the input frequency signal to a serial, four digits, BCD code. The code is recorded twice per frame by chopping the bits with a 250 Hz signal. The frame lasts 5 seconds after which a command is sent to the main unit advancing the multiplexer one step ahead. The reading unit consists of a second small tape recorder and a decoding circuit. The tape is played back 15 times faster than the recording speed. Synchronization and bits identification are based on counting the (original) 250 Hz chopping signal. This eliminates the problem due to wow flutter and non constancy of tape speeds. The serial BCD code is converted to a parallel code to facilitate printing or tape-to-tape transfer, for computer compatibility. The use of non-expensive tape decks as well as integrated circuit modules reduces markedly the price of the system without compromising on accuracy or reliability.
    • Design of Airborne S-Band Telemetry Antennas

      Weinschel, H. D.; New Mexico State University (International Foundation for Telemetering, 1968-10)
      The change from VHF to UHF for telemetry requires new antenna designs rather than the scaling of the antennas now used for the UHF frequencies. The reason for this is that the vehicle dimensions at UHF, in particular the rocket diameters, will be of the order of several wavelengths. A common method to obtain a nearly omnidirectional radiation pattern at VHF is to mount two or four element antenna arrays on the vehicle. This is sufficient since the wavelength for the presently used telemetry frequencies is approximately 50 inches and the array spacing rarely exceeds a half wavelength. The radiation pattern from such closely spaced unit radiators exhibits only minor scalloping which does not present a problem in the data acquisition. At the UHF frequencies, the array spacing, in wavelength, is increased by a factor of ten resulting in an interference pattern with narrow lobes and deep nulls. If the mechanical design limitations permit it, it is possible to design unit radiators which will give cardioid or nearly omnidirectional patterns for a single polarization component. Two such antennas are described. They are the axially mounted turnstile and the radial waveguide antennas.
    • Digital FM-Tutorial

      Salz, J.; University of Florida (International Foundation for Telemetering, 1968-10)
      A review of the state of knowledge of digital FM techniques is undertaken. The digital FM signal and its spectral properties are first discussed. We then turn to the analysis of discrimination detection and review a recently proposed phenomenological model from which the error causing mechanism can be understood. We use this model to derive estimates of error-rate as a function of pertinent system parameters. The results obtained for practically instrumented systems are then compared with the ideal. The paper concludes with a discussion of some computer-aided analysis capable of predicting the performance of digital FM systems operating over the dispersive gaussian channel.
    • Digital-Data Transition Tracking Loops

      Lindsey, W. C.; Anderson, T. O.; University of Southern California; Jet Propulsion Laboratory (International Foundation for Telemetering, 1968-10)
      This paper is devoted to the problem of tracking data-transitions in digital communication systems by means of decision-directed phase-tracking loops. Such techniques are of interest because these methods provide the receiver with a knowledge of the time instants when the modulation may change states without using the additional transmitter power. The results presented are useful in designing synchronizing circuitry for a wide variety of digital systems. One particular system mechanization plan is presented.
    • A Double Sideband-Quadrature Carrier Multiplex Telemetry System

      Gutwein, Joseph M.; Annese, Jerald F.; ADCOM (International Foundation for Telemetering, 1968-10)
      A novel FDM telemetry technique was developed consisting of a double sideband-quadrature carrier multiplexing system (DSB-QCM). Each subchannel in the DSB-QCM system carries two completely overlapping DSB data signals, one double-sideband modulated on the subcarrier itself, and the other on a quadrature version of the subcarrier. Demodulation with cophasal and quadrature subcarriers enables simultaneous data extraction from each channel within acceptable distortion levels. The feasibility and practicability of such a DSB-QCM telemetry system is discussed in this paper. Crosstalk levels between the quadrature multiplexed channels were measured and guardband requirements between adjacent channels were assessed for a modem comprised of three pairs of DSB-QCM channels. Crosstalk levels between uniformly loaded DSB -QCM channels were below 2% and guardband requirements equivalent to conventional DSB systems were observed. The DSB-QCM performance was also examined as a function of input SNR with two competing subcarrier synchronization methods. Subcarrier synchronization by means of synthesized reference tones coherently derived from a single pilot was demonstrated to be superior in The presence of noise to a channel reference approach in which each data channel must synchronize its own subcarrier. The major conclusion from this investigation is that DSB-QCM/FM telemetry combines the advantages of both SSB/FM and DSB/FM by accommodating as many data channels as SSB/FM but with low distortion data processing and the dc data response characteristic of DSB/FM.
    • The Effect of Coding on Rate Equalization of Digital Channels

      Butman, S.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1968-10)
      The pulse stuffing technique for rate equalization of digital channels is generalized in this article to the stuffing of a sequence of pulses (a word), which can be coded. The extra capacity needed for signaling the stuffed word decreases exponentially with the number of pulses in it, and may, in fact, be eliminated at a negligible increase in the error rate of the channel.
    • The Effects, Measurement, and Analysis of Flutter in Instrumentation Recorders

      Moore, Laurence; Micom, Inc. (International Foundation for Telemetering, 1968-10)
      As instrumentation recorders are improved to provide wider bandwidths and shorter recorded wavelengths, the effects of flutter and attendant time base distortion severely limit the potential for accurate recording and retrieval of data. The effects of flutter on typical classes of data is given and the measures necessary to determine flutter with high accuracy shown. Since the degrading effects of flutter depend upon the application and the characteristics of the flutter, means of analyzing flutter both in the time domain and in the frequency domain are necessary. A self contained instrument for accurate measurement and analysis of flutter sensitive enough for the most sophisticated transports is described, as are necessary conditions for its use.
    • Errors Resulting from Channel Filters and Adjacent Channel Crosstalk in DSB/SC Telemetry Systems

      Salter, W. E.; Frost, W. O.; Sperry-Rand Corporation; Marshall Space Flight Center (International Foundation for Telemetering, 1968-10)
      The waveform distortion resulting from adjacent channel crosstalk and from amplitude and phase nonlinearity in channel filters limits the minimum channel spacing, and hence the bandwidth utilization efficiency of a double sideband/suppressed carrier (DSB/SC) telemetry link. The paper presents results of an analysis defining the minimum achievable mean-square error when Butterworth filters are used in the DSB demodulator/demultiplexer. With data inputs consisting of band-limited random signals, solutions are given for various combinations of data order, filter order, channel spacing, and filter cut-off. The trade-off between waveform distortion and channel spacing is illustrated, and optimum locations for the filter cut-off are defined. The irremovable error based on Weiner optimum filter theory is presented as an interesting basis for comparison.
    • Expected Number of Spikes of Phase Locked Loop Demodulators

      Osborne, P. W.; Schilling, D. L.; Polytechnic Institute of Brooklyn (International Foundation for Telemetering, 1968-10)
      A new method is presented for finding the expected number of spikes in a phase locked loop of any order, with or without modulation. The procedure can also be employed to determine the threshold of FMFB, FM discriminators and the Maximum Likelihood Estimator. The low pass equivalent gaussian noises x(t), y(t) in the differential equation describing the system (PLL or FMFB) are replaced by the deterministic time functions (Conditional Expectations) 1) E[x(t)/x(0), ẋ(0)] 2) E[y(t)/y(0), ẏ(0)] and solved on a digital computer. The mid spike time (t=0)is taken to be the time when x(0) (quadrature noise)=0, and a surface or surfaces in ẋ(0), y(0), ẏ(0) space are determined which indicates the region A where spikes in the demodulator are obtained. From this the expected number of spikes per second is calculated. Results are presented for the first, second, and third order phase locked loops, and for an ordinary FM discriminator (which can be shown to be equivalent to a PLL of infinite gain). The second order loop used a constant plus integral filter, while the third order loop used a constant plus integral plus double integral filter.
    • Flight and Laboratory Testing of a Double Sideband FM Telemetry System

      Richardson, Robert B.; Harney, Paul F.; NASA Flight Research Center (International Foundation for Telemetering, 1968-10)
      This paper discusses the NASA Flight Research Center's laboratory and preliminary flight evaluation of a double sideband suppressed carrier constant-bandwidth telemetry system that will be used as an airborne high-frequency data recorder. Some practical limitations are illustrated, and laboratory and flight-test results are compared. No attempt is made to compare this system with systems using other forms of modulation. Results obtained using an RF link are compared with magnetic tape recording of data. Calibration requirements are included for each system.
    • Frequency Feed-Forward-An Open Loop Approach for Extending the Threshold and Linearity of FM Demodulators

      Pelchat, M. G.; Boor, S. B.; Radiation Incorporated (International Foundation for Telemetering, 1968-10)
      This paper describes Frequency Feed-Forward, an open-loop technique for lowering the FM threshold. The amount of threshold improvement with standard discriminators is discussed and experimental results with sinewave and gaussian modulation are given.