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Radio navigation systems such as Loran C,D operate on ground waves over distances up to 3000 or 4000 km from the transmitters. If the ground is inhomogeneous and irregular, the wave propagation may be considerably different from the classical smooth,...

High altitude nuclear detonations yield X-rays which produce intense ionization in about 1 μs at heights much lower than those of the normal D region. The ionization begins to decay immediately. This leads to a very complicated profile of ionization...

Modulation techniques for high frequency (HF) data transmission for the Integrated Global Ocean Station System (IGOSS) are discussed. Noncoherent frequency-shift-keying (NCFSK) and time-differential phase-shift-keying (TDPSK) systems are preliminari...

This report describes a digital computer program for simulating ocean data transmission systems that use high frequency radio. It is intended for use in the design and operation of the Integrated Global Ocean Station System (IGOSS) and the Nati...

The feasibility of angle diversity reception over a 404 km obstacle­-diffraction link in southern Europe was investigated during the summer of 1969. The primary objective of the measurement program was to determine the effectiveness of an experiment...

Comparisons are made between all the past measurements of Minuteman launch control type receivers, and these measurements are compared with the theoretical performance for receivers of this type acting in atmospheric noise. Comparisons are made for b...

The National Data Buoy Development Project has been undertaken by the U.S. Coast Guard to satisfy a critical need for additional marine environmental data. The concept of using a network of buoys to collect such data has been endorsed by a number of...

This study presents one-way error correcting techniques for IGOSS (Integrated Global Ocean Station System) channels. Emphasis is on applicable HF radio experiments and alternative simple implementations. The "most promising" 1/2 rate code for IGOSS i...

1. The F2-region ionospheric response to individual internal gravity waves is calculated as a function of the azimuth of wave propagation. The physical basis for the great anisotropy of the ionospheric response is discussed. 2. We present computer ...

This report summarizes and presents in mathematical, graphical, and tabular form the fundamental characteristics of basic analog and digital modulation processes used in the Air Traffic Control (ATC) communication system. Single channel modes of ...

This report describes a study by the Institute for Telecommunication Sciences (ITS), to plan a moderate expansion of the National Crime Information Center communication system. Improvements discussed are transmission of data at higher rates than curr...

Use of a decibel plot for the Bessel function makes it a simple task to obtain the single tone peak deviation of FM radio systems. The procedure offers ways to calibrate deviation meters, supplement the carrier disappearance technique, and check the...

System design questions associated with the development of an ocean data HF transmission system for the Integrated Global Ocean Station System (IGOSS) and the National Data Buoy Systems are considered. These include (1) development of a computer mod...

Swept frequency (CHIRP) modulation is analyzed as to its suitability for use in the Integrated Global Ocean Station System (IGOSS), a system for the collection of synoptic data from ocean platforms (buoys and/ or ships) using high frequency (HF) radi...

This report proposes and compares convolutional codes with the (15,5) BCH code. Word-error probabilities are computed for each of the codes with the convolutional codes performing at least an order of magnitude better than the (15,5) BCH code. The co...

This paper describes instrumentation for recording digitally the relative phase and amplitude of MF and HF radio signals back­scattered from ocean waves. Eight stepped frequencies, two spaced receiving antennas, and four different ranges are used. T...

Predictions of tropospheric transmission loss over irregular terrain using the computer methods described by Longley and Rice (1968) are compared with measurements, to determine their limits of applicability and define the boundary conditions for the...

Rain gauge data measured at the sub-common volume points when converted to an equivalent radar reflectivity and plotted in terms of a cumulative distribution correlates well with the similar cumulative distributions for the bistatic reflectivity for ...

This report reviews the techniques for calculating position with the Loran navigation system, including the use of phase correction factors computed for ground wave propagation over a smooth spherical earth. If the earth is rough or inhomogeneous, th...

A computer program. for calculating ground wave propagation in an ionized atmosphere is documented and listed. The conductivity of the atmosphere can vary in an arbitrary way with altitude. The notion of continuous stratification of the profile has b...