Engineering topics

Fischer, J. P.

Publications and source records attributed to Fischer, J. P..

10 records

NASA NTRS1982

Bi-directional communication interface for microprocessor-to-system/370

The design and operation of a bi-directional communication interface between a microcomputer and the IBM System/370 is documented. The hardware unit inter-connects a modem to interface to the S/370, the microcomputer with an EIA I/O port, and a terminal for sending and receiving data from either the microcomputer of the S/370. The software necessary for the two-way interface is also described. This interface was designed so that no modifications need to be made to the terminal, modem or microcomputer.

Fischer, J. P.↗

NASA NTRS1982

A microcomputer-based position updating system for general aviation utilizing Loran-C

Modern digital electronic technology is used to produce a device to convert LORAN C to useful pilot information using a simple software algebra and low cost microprocessor devices. Results indicate that the processor based LORAN C navigator has an accuracy of 1.0 nm or less over an area typically covered by a triad of Loran C stations and can execute a position update in less than 0.2 seconds. The system was tested in 30 hours of flight and proved that it can give reliable and accurate navigation information. Methods of converting time differences to position, design considerations for the microcomputer system, and the system for coordinate conversion are discussed. Testing with predetermined points and possible fixes for errors are also considered.

Fischer, J. P.↗

NASA NTRS1981

Results of a Loran-C flight test using an absolute data reference

A closed circuit flight test was conducted using VORs and NDBs as reference points. The Loran-C data collected during the flight was then compared against a reference provided by a discrete address beacon system facility. Information on the equipment configuration in the aircraft, the flight procedure, and the results obtained are presented.

Fischer, J. P.↗

NASA NTRS1981

Bi-directional communication interface for microprocessor-to-system/370

The design and operation of a bi-directional communication interface between a microcomputer and the IBM System/370 is documented. The hardware unit interconnects a modem to interface to the S/370, the microcomputer with an EIA I/O port, and a terminal for sending and receiving data from either the microcomputer or the S/370. Also described is the software necessary for the two-way interface. This interface is designed so that no modifications need to be made to the terminal, modem, or microcomputer.

Fischer, J. P.↗

NASA NTRS1980

Results of a Loran-C flight test using an absolute data reference

A closed circuit flight test was conducted in the Boston area using VOR's and NDB's as reference points. The Loran-C data collected during the flight was then compared against a reference provided by the Discrete Address Beacon System (DABS) facility at Lincoln Laboratories. A MIT crew used a commercial receiver and recorded Loran-C time differences which would also be compared with the data provided by the DABS facility and eventually with the data collected by Ohio University. The Ohio University low-cost receiver was used for this test which was conducted in the Ohio University DC-3 flying laboratory. The Loran-C time-difference data was recorded with a microcomputer data collection system and stored on magnetic tape for subsequent analysis. The MIT receiver was also on board the DC-3, and recorded its data on a cassette tape which was later used by the MIT crew for data analysis. The equipment configuration in the aircraft, the flight procedure and the results obtained from the data collected with Ohio University's receiver and recording system are described.

Fischer, J. P.↗

NASA NTRS1979

Data reduction software for LORAN-C flight test evaluation

A set of programs designed to be run on an IBM 370/158 computer to read the recorded time differences from the tape produced by the LORAN data collection system, convert them to latitude/longitude and produce various plotting input files are described. The programs were written so they may be tailored easily to meet the demands of a particular data reduction job. The tape reader program is written in 370 assembler language and the remaining programs are written in standard IBM FORTRAN-IV language. The tape reader program is dependent upon the recording format used by the data collection system and on the I/O macros used at the computing facility. The other programs are generally device-independent, although the plotting routines are dependent upon the plotting method used. The data reduction programs convert the recorded data to a more readily usable form; convert the time difference (TD) numbers to latitude/longitude (lat/long), to format a printed listing of the TDs, lat/long, reference times, and other information derived from the data, and produce data files which may be used for subsequent plotting.

Fischer, J. P.↗

NASA NTRS1979

Results of the second flight test of the Loran-C receiver/data collection system

The components of the Loran-C navigation system which were developed thus far are a phase-locked-loop receiver and a microcomputer development system. The microcomputer is being used as a means of testing and implementing software to handle sensor control and navigation calculations. Currently, the microcomputer is being used to collect and record data from the receiver in addition to development work. With these components, it was possible to record receiver data over a period of time and then reduce this data to obtain statistical information. It was particularly interesting to load the equipment developed in the laboratory into an aircraft and collect data while in flight. For initial flight tests, some important considerations were how well the entire system will perform in the field, signal strength levels while on the ground and in the air, the amount of noise present, changing of signal-to-noise ratio for various aircraft configurations and maneuvers, receiver overloading due to other equipment and antennas, and the overall usefulness of Loran-C as a navigation aid.

Fischer, J. P.↗

NASA NTRS1978

Initial flight test of a Loran-C receiver/data collection system

Development of a low cost Loran C receiver for general aviation use is discussed. The preparation and procedure of a flight test conducted with a receiver design which utilizes a phase locked loop oscillator to track the Loran C signals is described. It is indicated that such a receiver is a viable alternative for future work in developing a low cost Loran-C navigator.

Fischer, J. P.↗

NASA NTRS1978

Loran-C time difference calculations

Some of the simpler mathematical equations which may be used in Loran-C navigation calculations were examined. A technique is presented to allow Loran-C time differences to be predicted at a location. This is useful for receiver performance work, and a tool for more complex calculations, such as position fixing.

Fischer, J. P.↗

NASA NTRS1978

A video display interface for the LORAN-C navigation receiver development system

A microprocessor-based development system was designed and fabricated for prototype test of navigation receiver designs. During use of this system in the development of low-cost LORAN-C receiver/processor concepts, the limitations of the integral KIM-1 display were severely felt. It was to augment this numerical display that the video character display was produced. The circuit design presented meets the need for a flexible-format display capable of driving a small standard video monitor with only minimal demands upon microprocessor memory and MPU cycles.

Fischer, J. P.↗