VHF Radio Waves Research Articles

Updates on the measurement of the speed of gravity using LDVs and MEMS resonators

Five years ago, at the XIII AIVELA conference, a project was presented by the author for the laboratory determination of the speed of propagation of the gravitational interaction using a vibrating tungsten disc as source of a local gravitational perturbation and a high-Q silicon resonator as gravitational antenna. Using laser Doppler vibrometers to track the vibrations of the transmitter and of the receivers, the speed of propagation of gravity would have been calculated from their measured phase difference. Numerous developments happened in the project since then, from the construction and acquirement of important components of the generator of dynamic Newtonian fields, to the experimental measurement of the speed of VHF radio waves in the near-field region as a preparatory technical test for handling and elaboration of the corresponding gravitational data. This latter experiment produced unexpected superluminal results, making it worthy of further study. The results of the test also broadened the scope of expectations and possible interpretations of the results of the gravitational experiment, including the additional role of an indirect assessment of the existence of gravitons.

Equatorial Plasma Bubbles: A Review

The equatorial plasma bubble (EPB) phenomenon is an important component of space weather as the ionospheric irregularities that develop within EPBs can have major detrimental effects on the operation of satellite-based communication and navigation systems. Although the name suggests that EPBs occur in the equatorial ionosphere, the nature of the plasma instability that gives rise to EPBs is such that the bubbles may extend over a large part of the global ionosphere between geomagnetic latitudes of approximately ±15°. The scientific challenge continues to be to understand the day-to-day variability in the occurrence and characteristics of EPBs, such as their latitudinal extent and the development of irregularities within EPBs. In this paper, basic theoretical aspects of the plasma processes involved in the generation of EPBs, associated ionospheric irregularities, and observations of their characteristics using different techniques will be reviewed. Special focus will be given to observations of scintillations produced by the scattering of VHF and higher frequency radio waves while they propagate through ionospheric irregularities associated with EPBs, as these observations have revealed new information about the non-linear development of Rayleigh–Taylor instability in equatorial ionospheric plasma, which is the genesis of EPBs.

GEORADAR AND RADIOIMPEDANCE DIAGNOSTICS OF THE SELENGA RIVER WATER AREA

The relevance of the work is determined by the fact that no radiowave methods have ever been used to study the water areas of rivers and lakes and their geoelectric sections within the Baikal natural territory (BNT) in winter time. The purpose of the research is to determine the electrical and geometric characteristics of the layered medium "ice – water – bottom soil" and the ice cover of the Selenga River on the BNT in the VLF-LF and VHF radio wave bands according to the data of instrumental radiophysical measurements by GPR and radio impedance methods, including the determination of the structure of the ice crossings over the Selenga River. Using the Selenga River as an example, consideration has been given to the results of combining VLF-LF and VHF methods of electromagnetic diagnostics of a layered medium in a wide range of radio waves (from tens of kilohertz to units of gigahertz). Radio impedance profiling and sounding in the VLF-LF bands with the IPI-300 equipment made it possible to determine the sub-bottom structure of the soil from the change in impedance and geoelectric section. GPR in the VHF band made it possible to differentiate the fine structure of the Selenga River in winter by thickness of snow, ice and water. The sounding involved the use of georadar "Oko-2" with antenna units "Triton" (central frequency 50 MHz), AB-400 (central frequency 400 MHz), AB-700 (central frequency 700 MHz), and AB-1700 (central frequency 1700 MHz). The thickness of ice of the road crossing in the Mostovoy microdistrict of Ulan-Ude city was 0.5–1.2 m – 0.1–0.2 m thicker than that beyond the road crossing. It was found that the presence of snow cover beyond the road crossing prevents the ice mass from freezing. Calibration sounding of ice with borehole drilling yielded ice dielectric constant ε=3.17. The specific electrical resistance (SER) of water from boreholes is 71–74 Ohm·m at a temperature of 1 °C. The methods used complement each other and provide a quantitative description of the object of research. The integration of various methods of radio wave diagnostics provides more detailed information on the structure of the layered medium "ice – water – bottom soil". The obtained results and the developed methods of radio impedance and GPR sounding and profiling of an inhomogeneously layered underlying environment in winter time can be used in engineering and geological surveys in the eastern and northern regions of Russia.

ANALISIS KEBERHASILAN AUTOMATIC IDENTIFICATION SYSTEM (AIS) PADA KAPAL TUG BOAT LEO POWER 2206

Automatic Identification System (AIS) is a navigation system capable of sending and receiving ship information with VHF radio waves and TDMA transmission. In an effort to improve ship safety, it is necessary to have an appropriate navigation device to be able to send ship information accurately and quickly. With the disturbance that occurs in the process of sending information through radio frequencies, it is necessary to have an understanding of the process of sending information using radio frequencies, especially in AIS technology. The success rate of this tool is closely related to the safety of passengers and crew. In this study, the authors conducted direct observations and interviews related to the performance and success rate of the AIS tool with a sample of sending data for 30 seconds with a case study on the use of AIS on the Tug Boat Leo Power 2206.

The Concept of Intelligent Radiocommunication System for Support Decision of Yacht Captains in distress situations with use of neural network computer systems

The paper presents a new concept of a yacht Radio-communication system for Support Decision of the yacht captain in case of a collision situation. This has an impact on reducing the risk of loss of life of the yacht crew and the loss of property, including the yacht. The key problem in a collision situation is to be able to contact with SAR Maritime Rescue Centres. This paper proposes a model of an intelligent system based on the method of artificial neural networks ANN, which allows to support in making the right decision by the captain in case of life threatening danger on board of the yacht. The paper presents an example of The Decision Support System for a specific yacht location in relation to the existing RCC-SAR zones A1, A2, A-GSM and the propagation range of VHF, GSM and MF radio waves, with a worked out decision of the possible closest distance from the zone, allowing the use of these devices to call for help and carry out an effective rescue operation.

THE SURFACE IMPEDANCE OF THE "THIN ICE - SEA" AND "THICK ICE - SEA" STRUCTURES IN VLF-VHF RADIO WAVE BANDS

To calculate the propagation of the electromagnetic field over the two-layer struc-ture "ice - sea", the areas of applicability of the impedance boundary conditions are determined depending on the thickness of the ice and the angle of incidence of the vertically polarized wave in the range of 0.01-420 MHz. The article examines the structures "thin ice - sea" and "thick ice - sea" (six models of ice cover). The ice thickness varied from 0.03 to 9 m. The results are needed to calculate the atten-uation function and the field level in the VLF, LF, MF, HF, VHF radio wave bands. It is shown that for the structure “ice - sea” it is important to take into account the dependence of the surface impedance on the angle of incidence for over-the-horizon radar systems in the HF radio wave range. In the VHF range the frequency bands are determined for ice 80 cm thick, in which the impedance boundary condi-tions are applicable.

Probabilistic and statistical estimation of VHF radio wave propagation taking into account refraction in the troposphere

Probabilistic and statistical estimation of VHF radio wave propagation taking into account refraction in the troposphere

Anomalous Propagation of Radio Waves from Distant ILS Localizers Due to Ionospheric Sporadic‐E

AbstractThe ionospheric sporadic‐E (Es) layer occasionally causes anomalous propagation (AP) of VHF radio waves to distant locations. This effect, EsAP, may cause interference to VHF radio operation above 100 MHz. Recent study showed that VHF air navigation signals from distant stations are frequently observed when Es occurs. The observed frequencies includes channels of VHF omnidirectional radio range (VOR) and instrument landing system localizer (ILS LOC). The study showed that EsAP signals can be very strong and frequently exceeded the allowable interference limit of navigation receivers. In this paper, we focus on EsAP on ILS LOC channels using the data obtained in the previous study. A series of extremely strong signals was observed on an ILS LOC frequency at Kure, Japan, on 15 May 2014 when an ionosphere sounder observed high‐density Es. The source of the signal was identified as an ILS LOC‐type direction aid (LDA) at Hualien, Taiwan. During the same period, several EsAP signals were observed on other ILS LOC channels, but their strengths were less significant. Analysis showed the causes of the strong signal from Hualien LDA: (1) the center of the narrow radio beam passed through the region very close to the receiver site; (2) the elevation angle of the propagation path was very close to that of the actual beam center. Statistics showed that there were several outstanding EsAP events of which source was Hualien LDA. This study suggests that if similar conditions exist, radio interference to ILS LOC receiver can happen on any ILS LOC channels.

An Environment and Ionosphere to Examining Optical and Radio of Lightning-Related Wonders

The observing as well as sounding of lightning releases and their related phenomea (mesospheric optical outflows and so on.) has been performed by radio and optical estimations. We focus on the winter lightning in the Hokuriku region (Japan Sea side) of Japan, since it is critical to explore whether lighting releases in the Hokuriku territory (entire spatial scale is generally little in correlation with the traditional summer lightning in the US) could trigger the mesospheric optical emanations. The optical perception of those mesospheric emanations and the comparing radio sounding by ELF and VHF radio waves of their parent lightning, have been accounted for. The watching frameworks are initially exhibited, and our most recent observational certainties on the mesospheric outflows in the Hokuriku territory, their parent lightning and some PC recreations on the sprite start, are introduced.

Anomalous propagation of VHF radiowaves behind the horizon in the seismic region

A theory of electromagnetic radiation generation by random electric discharges in the troposphere and VHF radiowave scattering by these discharges has been developed. The discharge model, which makes it possible to calculate the spatiotemporal distribution of the discharge channel conductivity depending on the electric current value in this discharge, has been obtained. The electromagnetic radiation spectrum in the troposphere occupied by random discharges has been calculated. VHF electromagnetic wave scattering by random electric discharges in the troposphere has been considered. Equations have been derived, and the method for calculating the average value of the electromagnetic wave field scattered by random discharges has been developed. The calculations indicated that the scattered wave field amplitude is much larger than the diffraction wave field amplitude behind the horizon. The theoretical results agree with the observations of the electromagnetic radiation and VHF transmitter signals behind the horizon relative to the earthquake epicenter during the earthquake preparation.

Estimation of Direction of Arrival of VHF Radio Wave by Interferometers

Estimation of Direction of Arrival of VHF Radio Wave by Interferometers

Some preliminary investigations on the propagation of V.H.F. radio-waves at 126Mc/s in Mountainous terrain

This Paper deals with the propagation of VHF radio waves at 126Mc/s within a distance of 2km, on six different paths. Practically observed field strengths have been considered and compared with those theoretically calculated. The observations indicate a difference of about 10-12db on average from the predicated figures for vertically polarized waves which is expected to arise due to absorption by vegetation and the effect of hillocks close by. The differences tend to zero in simpler cases of diffraction not complicated by vegetation etc. An extreme difference of even 25db was observed to be accounted by absorption due to surroundings of vegetation, and buildings.

A VHF interferometry system for detecting anomalous propagation of FM radio broadcasting waves related to earthquakes and some preliminary results

AbstractEarthquake‐related anomalous electromagnetic phenomena have been reported in various frequency ranges over the past few decades. Investigation of the anomalous propagation of VHF transmitter waves is a promising approach to short‐term prediction and crustal activity monitoring. Anomalous propagation is believed to be generated by disturbances of the atmosphere above the epicenter or along the propagation path prior to large earthquakes. Consequently, over‐the‐horizon propagation has been received. A recent study shows that the appearance of anomalies was significantly enhanced within 5 days of earthquakes with M ≥4.8. However, there is no information on the scattering location, that is, on the direction of wave arrival. Therefore, a simple interferometer system for VHF radio waves to identify the space‐time position of earthquake‐related atmospheric disturbances has been developed and installed at Chiba University. This paper describes the newly developed interferometer system and presents the results of fundamental tests to evaluate the performance of the new interferometer at Chiba. Data on over‐the‐horizon propagation of VHF radio waves obtained from 1‐year continuous measurement at Chiba are described. These are possible radio duct propagations and possible earthquake‐related anomalous propagations. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 16–24, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22303

The Ionospheric Effect on the Determination of Lightning Source Location using VHF Radio Waves by Satellite Remote Sensing

The Ionospheric Effect on the Determination of Lightning Source Location using VHF Radio Waves by Satellite Remote Sensing

VHF Radio Wave Observations by Maido-1 Satellite and Evaluation of Its Relationship with Lightning Discharges

VHF Radio Wave Observations by Maido-1 Satellite and Evaluation of Its Relationship with Lightning Discharges

Observations of anomalous propagation of VHF radio wave due to sporadic-E and tropospheric duct in Hiroshima and Aso

In non line-of-sight VHF radio wave observation, anomalous propagations due to ionospheric sporadic-E (Es propagation) and tropospheric duct (tropospheric ducting) have been frequently observed. They are known to cause an interference problem in the television, radio broadcasts and wireless communications, so that it is important to understand them. In order to make clear the characteristics of the anomalous propagations, we have observed over-horizon FM radio waves in VHF band for six years in Hiroshima and Aso. For analyses of large amounts of data set observed over years, it is important to classify and extract the radio waves automatically. In this paper, we show a method to classify above two anomalous propagations automatically. Procedures of the method are based on their propagation characteristics and received signal strength. Further the anomalous propagations and broadband noises are separated using dual frequency method. In order to evaluate the method, we examined the occurrence of the Es propagation and tropospheric ducting detected by the above method using the data observed from 2005 to 2010. It was found that the Es propagations were mostly observed in summer season and more frequently observed months in a year were June and July. Further, they were frequently observed from 10 to 12 and from 16 to 18 o’clock in a day. These results had the same tendency as past observations at mid-latitude. On the other hand, the tropospheric ducting was observed from night to morning time in spring and fall at Aso observatory.These results were consistent with past observations of occurrences of inversion layer in the troposphere from fall to spring. In contrast, it was confirmed that there were few tropospheric ducting in summer season while the past observations reported the inversion layer occurred. Since propagation characteristics of the FM radio waves have been clearly shown, it was confirmed that the classification method worked effectively.

Study of night time VHF ionospheric scintillations near the crest of equatorial Appleton anomaly Indian Station, Udaipur (24.6°N, 73.7°E)

This paper presents the results of percentage occurrence of night time VHF ionospheric scintillations characteristics of radio beacon signals of 244/250 MHz transmitted from Fleet Satellite (positioned at 73°E Longitude) received over Udaipur (24.6°N, 73.7°E, Dip angle 35°) during different epochs of solar activity periods from March 1986 to April 2000. The long term observations of VHF scintillation phenomenon, spanning a solar cycle (1986 to 2000) which covers low, mid as well as high solar activity period, has shown the consistent nocturnal temporal hourly, seasonal and solar cycle variations in scintillation occurrences. The night time VHF radio wave scintillations has been found to be at maximum percentage occurrence during the equinoxes months and less during winter and the least during summer months in all the epochs of solar activity period. The monthly variations of percentage occurrences of VHF ionospheric scintillation activities are seen to be increased during high solar activity years and also showed that highest values of percentage of occurrences in equinoctials months during high solar activity years. The prominent feature of discrete patchy nature of night time VHF amplitude scintillations specifically, over Equatorial Appleton anomaly region, is also presented in the light of seasonal and solar activity dependence of scintillation occurrences and patches duration. The results of present observations are also compared with the earlier works of similar stations.

VHF Interferometry System for Detecting Anomalous Propagation of FM Radio Broadcasting Wave Related to Earthquake and its Preliminary Result

Earthquake-related anomalous electromagnetic phenomena have been reported in various frequency ranges in a few decades. Investigation on the anomalous propagation of VHF transmitter waves is one of promising approaches on the short-term prediction and crustal activity monitoring. The anomalous propagation is considered to be generated by disturbances of the atmosphere above the epicenter or along the propagation path prior to large earthquakes. Consequently, over-horizontal propagation has been received. A recent study shows that the appearance of anomalies was significantly enhanced within 5 days before earthquakes with M ≥ 4.8. However, there is no information on the scattered place, that is, the direction of wave arrival. Therefore, a simple interferometer system for VHF radio wave to identify the position between space-time of earthquake-related atmospheric disturbances has been developed and installed at Chiba University. In this paper, we will show you the developed interferometer system and results of fundamental tests to evaluate the performance of developed and installed interferometer at Chiba. In addition, facts on invisible propagation of VHF radio wave obtained from 1-year continuous measurement at Chiba are described in this paper. Those are possible radio duct propagations and possible earthquake-related anomalous propagations.

The relationship between signal intensity and maximum observed frequency in long-distance propagation of VHF radio waves based on the reflection from the ionosphere

The relationship between signal intensity and maximum observed frequency in long-distance propagation of VHF radio waves based on the reflection from the ionosphere

Long-Distance Propagation of VHF Radio Waves due to the Effect of the Equatorial Anomaly

Observation of 48.25-MHz radio waves transmitted from Bangkok, Thailand, was carried out at Tateyama, Japan, during 2001. Since the radio wave propagates through a crest of equatorial anomaly, which disturbs stratified structure of the ionosphere, it is conceivable that the propagation of the radio wave is affected by three-dimensional structure of the ionosphere. Seasonal and diurnal variations of the signal intensity are quite similar to ƒ0F2 above Guangzhou and also Okinawa, which are located on the great circle path between Bangkok and Tateyama. Using ray-tracing calculations with the distribution of the electron density determined by IRI model, it is also confirmed that the radio wave propagates to Tateyama because of one-hop reflection in the ionosphere and that MUF is mainly dependent on ƒ0F2 above the midpoint between Bangkok and Tateyama. Although the value of ƒ0F2 is almost constant, MUF calculated by the ray-tracing treatment decreases around 14 JST in fall and winter. This decrease is also detected in the observational result of the signal intensity of the radio wave received at Tateyama. The ray tracing calculation shows that the decrease of MUF is due to tilt of the distribution of electron density, which is noticeable in developing the equatorial anomaly. Then discussing the propagation characteristics of 48.25-MHz radio waves crossing equatorial anomaly region, it is important to consider not only the parameters of the ionosphere, e.g. ƒ0F2, but also the tilt of the distribution of electron density.