Aspects of HF radio propagation (original) (raw)
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Propagation of HF radio waves over northerly paths: measurements,simulation and systems aspects
Large deviations in the direction of arrival of ionospherically propagating radio signals from the Great Circle Path (GCP) have serious implications for the planning and operation of communications and radiolocation systems operating within the HF-band. Very large deviations are particularly prevalent in the polar and sub-auroral regions where signals often arrive at the receiver with bearings displaced from the great circle direction by up to ±100° or more. Measurements made over several paths are presented in this paper, and the principle causes of off-great circle propagation outlined. Significant progress has been made in modelling the propagation effects and work is now in hand to incorporate the results into tools to aid the planning and operation of HF radio systems operating at northerly latitudes.
Radio Science, 2007
1] Prediction of the propagation characteristics of HF signals is an important aspect in the planning and operation of radio systems operating within that frequency band. Various computer codes have been developed by a number of organizations for this purpose. These prediction techniques assume that propagation is along the great circle path and ignore the effects of various large-scale ionospheric structures that can be present in the northerly ionosphere and result in propagation well displaced from the great circle path. This paper reports on a statistical analysis of observations of the direction of arrival and signal strength, and their comparison with VOACAP predictions for four paths, two roughly tangential to the midlatitude trough, one trans-auroral, and one entirely located within the polar cap. Citation: Stocker, A. J., E. M. Warrington, and D. R. Siddle (2007), Comparison between the measured and predicted parameters of HF radio signals propagating along the midlatitude trough and within the polar cap, Radio Sci., 42, RS3019,
Article 12 Ionospheric Non-linear Effects Observed During Very-Long-Distance HF Propagation
Frontiers in Astronomy and Space Sciences, 2019
A new super-long-range wave propagation technique was implemented at different High Frequency (HF) heating facilities. The HF waves radiated by a powerful heater were scattered into the ionospheric waveguide by the stimulated field aligned striations. This waveguide was formed in a valley region between the E-and F-layers of the ionosphere. The wave trapping and channeling provide super-long-range propagation of HF heater signals detected at the Ukrainian Antarctic Academik Vernadsky Station (UAS) which is many thousand kilometers away from the corresponding HF heating facility. This paper aims to study the excitation of the ionospheric waveguide due to the scattering of the HF heating wave by artificial field aligned irregularities. In addition, the probing of stimulated ionospheric irregularities can be obtained from analyses of the signals received at far distance from the HF heater. The paper uses a novel method of scattering of the HF radiation by the heating facility for diagnostics of non-linear effects at the super-long radio paths. Experiments were conducted at three different powerful HF facilities: EISCAT (Norway), HAARP (Alaska), and Arecibo (Puerto Rico) and by using different far spaced receiving sites. The key problems for super-long-range propagation regime is the feeding of ionospheric waveguide. Then the energy needs to exit from the waveguide at a specific location to be detected by the surface-based receiver. During our studies the waveguide feeding was provided by the scattering of HF waves by the artificial ionospheric turbulence (AIT) above the HF heater. An interesting opportunity for the channeling of the HF signals occurs due to the aspect scattering of radio waves by field aligned irregularities (FAI), when the scattering vector is parallel to the Earth surface. Such FAIs geometry takes place over the Arecibo facility. Here FAI are oriented along the geomagnetic field line inclined by 43 degrees. Since the Arecibo HF beam is vertical, the aspect scattered waves will be oriented almost horizontally toward the South. Such geometry provides unique opportunity to channel the radio wave energy into the ionospheric waveguide and excites the whispering gallery modes.
Ionospheric Non-linear Effects Observed During Very-Long-Distance HF Propagation
Frontiers in Astronomy and Space Sciences
A new super-long-range wave propagation technique was implemented at different High Frequency (HF) heating facilities. The HF waves radiated by a powerful heater were scattered into the ionospheric waveguide by the stimulated field aligned striations. This waveguide was formed in a valley region between the E-and F-layers of the ionosphere. The wave trapping and channeling provide super-long-range propagation of HF heater signals detected at the Ukrainian Antarctic Academik Vernadsky Station (UAS) which is many thousand kilometers away from the corresponding HF heating facility. This paper aims to study the excitation of the ionospheric waveguide due to the scattering of the HF heating wave by artificial field aligned irregularities. In addition, the probing of stimulated ionospheric irregularities can be obtained from analyses of the signals received at far distance from the HF heater. The paper uses a novel method of scattering of the HF radiation by the heating facility for diagnostics of non-linear effects at the super-long radio paths. Experiments were conducted at three different powerful HF facilities: EISCAT (Norway), HAARP (Alaska), and Arecibo (Puerto Rico) and by using different far spaced receiving sites. The key problems for super-long-range propagation regime is the feeding of ionospheric waveguide. Then the energy needs to exit from the waveguide at a specific location to be detected by the surface-based receiver. During our studies the waveguide feeding was provided by the scattering of HF waves by the artificial ionospheric turbulence (AIT) above the HF heater. An interesting opportunity for the channeling of the HF signals occurs due to the aspect scattering of radio waves by field aligned irregularities (FAI), when the scattering vector is parallel to the Earth surface. Such FAIs geometry takes place over the Arecibo facility. Here FAI are oriented along the geomagnetic field line inclined by 43 degrees. Since the Arecibo HF beam is vertical, the aspect scattered waves will be oriented almost horizontally toward the South. Such geometry provides unique opportunity to channel the radio wave energy into the ionospheric waveguide and excites the whispering gallery modes.
Nasa Sti Recon Technical Report N, 1984
General analytical ~~nnulas derive~ ~thin a uniform approximation in a previous paper by the present authors are utdtzed for detennmmg the wave pattern of a vertically propagating HF wave that is totally or partially reflected from the ionosphere. The full three-dimensional wave is calculated accurately, als~ at the reflection point. Parameter values typical of ionospheric modification experiments at Arectb~ and Tromse are chosen. The influence of the geomagnetic field and collisions are properly t~ken mto account but notdinear and coupling effects are excluded. It is shown that the g~omagne.ttc ~eld affects the wave pattern strongly, especially in the Tromse case, and leads to a very htgh swelhng m the first wave maximum below the reflection point. an E Layer at Tromse for Different Critical Frequencies w .. J(2n~ x 3 ,,, km h, km wj(2n), kHz wcr/(2n), kHz Wee /(2n), kHz (}, deg v/(2n), kHz Case a
International Journal of Microelectronics and Digital Integrated Circuits, 2020
A ray tracing program which is an algorithm that can be used to describe the complex nature of the ionosphere has been developed using locally available resources. The International Reference Ionosphere (IRI) Ionospheric Model were incorporated into the program for evaluating electron density values. Complex refractive indices of the ionosphere were generated using Appletone-Hartree formula with no collision and magnetic field effects. The program applies Snell's law of refraction in generating signal's refraction. 2-D ray coordinates were generated and ray path was plotted. The illustration in the application of the program was done using an assumed transmission of 6.957 MHz radio frequency from Abuja (7.38 o E, 8.99 o N) in the direction of Lagos (6.52 o N, 3.38 o E), Nigeria. Results provided amongst others includes, distribution of electron density (Ne) for the day and night time; minimum value of Ne at night (0:00 UT), ascending in the morning (6:00 UT), maximum at or close to noon (12:00-14:00 UT) and descending in the evening (18:00 UT). Rays travel farther distance in the solstice seasons than in the equinox seasons. Radio waves leaving the earth at high transmission angles above the horizon may receive only slight bending due to refraction, and are lost to outer space. It is hoped that the program will find immense application in High Frequency (HF) radio communication industries, research industries, aviation industries, and other industries that make use of Earth-Space systems.
Measurements of the time-of-flight and direction of arrival of an HF radio signal on a sub-auroral path between Sweden and the U.K. are presented. During the day, as expected, the signal arrives from the great circle path (GCP) direction. However, at night, especially during the winter and equinoctial months, the signal often arrives at azimuths displaced from the GCP by up to 40°. Azimuths which are deviated to the north of the GCP may arise as a result of the signal being scattered by irregularities embedded in the poleward wall of the trough.
Observations of HF propagation on a path aligned along the mid-latitude trough
Advances in Space Research, 2009
Observations of the direction of arrival and time of flight of HF signals propagating on a 1400 km path oriented along the mid-latitude trough are presented. At night, the signal commonly arrives from directions offset from the great circle bearing by up to 80° and these events have been categorised into five main types. Statistics indicating how often these categories of propagation were observed in the period August 2006 to September 2007 are presented. The physical mechanisms which result in the off great circle propagation are also discussed.