HF Radio Systems Research Articles

SISTEM PENANGKAL PETIR DI GEDUNG TELEKOMUNIKASI DAN GEDUNG PAI MATSC

On Friday, 11 November 2022, there was damage to the radio link equipment in the HF and MSSR radio transmitter communication systems due to a lightning strike operating at the Makassar Air Traffic Service Center (MATSC) office. This lightning strike is a phenomenon that poses a threat to the operation of flight navigation services carried out by the MATSC branch of Perum LPPNPI. The purpose of this study is to evaluate the external lightning protection system that has been installed and also to determine the effectiveness of the conventional lightning protection system on the antenna tower next to the MATSC radio PAI building. This study uses quantitative research methods. Retrieval of data using the method of observation and measurement. The calculation results found that the PAI Building was included in category IV, meaning that the lightning strike hazard level is 80%. While the antenna tower has a protection level category III, which means it has a danger level of 90%. However, from the observations, only the tower antenna is provided with a conventional type of lightning rod, while the PAI Building does not have a lightning rod system. The calculation results show that the existing conventional lightning rod protection angle is around 35o with a protection radius of 16.58 m. So that with this radius, the PAI building does not fully get protection from the dangers of lightning strikes.
 
 Keywords: Lightning Protection System, Antenna Tower, PAI MATSC Building

Modern Solutions to Improve the Energy Efficiency of Radio Lines for the Technical Renewal of Radio Stations of Integrated Communication Systems

Promising tasks for improving radio equipment with increased energy efficiency, related to in-depth preliminary study and efficiency research using the stand of the chief designer, are considered. Initially, a theoretical factor analysis of the interference radio terminal energy efficiency with respect to evenly distributed over the spectrum is given. The problem of choosing a variant of digital modulation and parameters of a noise-resistant code from the condition of obtaining the least energy for the transmission of one bit of information at a given error probability per bit and the level of spectral noise density is examined. With regard to broadband signals, energy-efficient linearly frequency-modulated signals are allocated. In the case of narrowband signals, cognitive technologies for improving energy efficiency for radio paths with partially filled spectrum, tuning radio lines to the 'windows of the best transparency' of the spectrum, are studied. Their importance for VHF radio lines and HF radio systems with tuning to the optimal frequency by regular ionosphere sounding is noted. The features of cognitive radio networks development to improve the energy efficiency of radio facilities are considered. The ways of algorithms design for modem and noise-resistant encoder energy effective tuning to a given radio line conditions for testing in the stand of the Chief Designer are discussed. Priority tasks for improving radio equipment with increased energy efficiency have been specified. Urgent specific subtasks for elaboration at the stand of the Chief Designer are highlighted.

METHOD FOR INCREASING TRANSFER RATE
 IN HF RADIO SYSTEMS AND ITS IMPLEMENTATION
 (part 1)

A method for increasing the transfer rate in HF radio communication systems is proposed, which, in comparison with existing methods, allows it to be doubled without expanding the frequency band occupied by the communication channel. The block diagram of one of the variants of the HF radio communication system that implements the proposed method is presented. The analysis of the operation of the communication system in the absence of external interference and the influence of interference concentrated over the spectrum is carried out.

Spatial Correlation and Diversity of Low-Latitude Multipath Multimode HF Skywave Radio Channels

To support the reliability and coverage of long-range skywave HF radio communication systems, it is necessary to consider technologies that involve multiple links, such as site diversity, network relay, or cooperative communication. This paper reports a study on the spatial correlation of signals between two HF skywave links with a common end and the benefit of site diversity systems using such links. For this study, two links in a low-latitude region are considered, each with a groundrange of 3044 km and 1895 km, both having a common transmitter and different receivers separated 1900 km apart. The correlation is evaluated from the results of ray-tracing simulations, verified with measurements and simulations for different dates. This study confirms that the correlation between two HF links is low, which can be explained as being the result of sum of multiple paths with random, uncorrelated phase-shifts. The study also proves that site diversity using two convergent links with selective combining can provide diversity gain and reduce the probability of outage significantly. To enhance the benefit of site diversity, a joint space-frequency diversity involving two different frequencies with opposite diurnal characteristics on the primary and alternative link is recommendable.

HF Radio Systems and Techniques Announcement

Up to the 1960's most telecommunication between the continents was realized by large HF (3 to 30MHz) radio systems especially built for that purpose, using the ionosphere as a natural high altitude 'reflector'. Inventions such as adaptive beamforming, antenna diversity, and frequency diversity stem from the 1930's, an impressive achievement considering the technology of that time.

단파 스펙트럼 수신 모니터링 시스템 개발

태양 흑점 폭발로 인해 방출되는 전자파는 지구상 낮 지역의 전파 통신에 장애를 일으킨다. 전세계에서 사용하는 태양 흑점 폭발 경보의 등급은 Geostationary Operational Environmental Satellite의 X선 세기에 따라 분류되고, 통신 장애를 판단한다. 하지만 태양과 직하점이 지구 자전에 따라 변하기 때문에 동일한 경보라도 통신 장애 영향은 같지 않다. 이러한 문제를 해결하기 위해 단파 통신을 전파 스펙트럼으로 수신하고, 통신 두절 여부를 모니터링하는 시스템을 개발하였다. 이 시스템은 단파 스펙트럼을 실시간 측정한 후 매분마다 자동으로 신호대 잡음비를 산출하고, ITU 권고의 간섭기준에 비교하여 통신 두절 시간을 산출한다. Electromagnetic waves which are emitted from the Sun due to solar flare explosion can cause failures in HF radio communications in the day-side area of the Earth, that is so-call as Radio Blackouts. The international scale representing the severity of the Radio Blackouts is determined by the solar X-ray flux which is measured by United States Geostationary Operational Environmental Satellite. However, the scale is not always applicable to HF communication users in the different area on the Earth, because the HF communication effects depend not only on the X-ray strength but also on the subsolar point location. To solve this problem, we developed a HF radio spectrum monitoring system utilizing a spectrum analyzer. This system conducts a real-time measure of the HF spectrum, and automatically calculates signal to noise ratios and the occurrences of the HF blackouts as comparing with the interference level which is described from the ITU recommendation.

Extreme Space Weather Impact: An Emergency Management Perspective

AbstractIn 2010, the Department of Homeland Security's Federal Emergency Management Agency (FEMA) partnered with the National Oceanic and Atmospheric Administration's Space Weather Prediction Center (SWPC) to investigate the potential for extreme space weather conditions to impact National Security/Emergency Preparedness communications—those communications vital to a functioning government and to emergency and disaster response—in the United States. Given the interdependencies of modern critical infrastructure, the initial systematic review of academic research on space weather effects on communications expanded to other critical infrastructure sectors, federal agencies, and private sector organizations. While the effort is ongoing, and despite uncertainties inherent with this hazard, FEMA and the SWPC did draw some conclusions. If electric power remains available, an extreme space weather event will result in the intermittent loss of HF and similar sky wave radio systems, minimal direct impact to public safety line‐of‐sight radio and commercial cellular services, a relatively small loss of satellite services as a percentage of the total satellite fleet, interference or intermittent loss of satellite communications and GPS navigation and timing signals, and no first‐order impact to consumer electronic devices. Vulnerability of electric power to an extreme geomagnetic storm remains the primary concern from an emergency management perspective, but actual impact is not well understood at present. A discussion of potential impacts to infrastructure from the loss of electric power from any hazard is provided using the 2011 record tornado outbreak in Alabama as an example.

HF radio communication systems: development, production and perspective solutions

The article contains the review of development of the Radio Research Development Institute Samara Branch in the area of creation of various equipment for the communication channels working in HF range. Thus presents system researches on a number of the main directions of a radio communication, development of antennas and antenna systems, including original designs in the form of ring lattices are allocated, examples of successful solutions of creation of the equipment with the improved noise stability and capacity. All development is accompanied by the corresponding information support and creation of special software products.

A Novel Approach to Study Regional Ionospheric Variations Using a Real-Time TEC Model

Since IGY (International Geophysical Year), through coordinated global observations, ionospheric research has been carried out by many countries. This effort primarily helped in the design and operation of HF radio wave communication systems. The Indian region covers a highly variable part of the equatorial electrojet and EIA (Equatorial Ionisation Anomaly) phenomena making its predictability difficult. With the advent of satellite communication and navigation, the need for accurate ionospheric TEC (Total Electron Content) models at global and regional scales has been stressed. The GAGAN (GPS Aided Geo Augmented Navigation) project jointly undertaken by the Indian Space Research Organisation (ISRO) and the Airport Authority of India (AAI) aims at effectively utilising the Global Navigational Satellite System (GNSS) to determine position coordinates accurately for aircraft precision landing applications. For this purpose the range errors are estimated by using a ground network of TEC stations spread over Indian region. The near simultaneous data collected from these dual frequency GPS stations can be used to generate the geo-referenced TEC values for various applications. The author has developed necessary algorithm and associated computer programmes for a real-time vertical TEC (VTEC) model based on TEC data collected from the GAGAN ground based network stations. The model has been tested and sample results presented here show that it adequately provides for the latitudinal resolution of 1° for the entire longitude span and also for two longitude blocks (73 - 83 & 83 - 93°E) separately. Cubic spline and bilinear interpolation techniques are used for filling up temporal and spatial data gaps. The model provides tabulated output of hourly average VTEC data with latitude for ready use, as well as graphical displays of VTEC maps and contours for monitoring purpose. The real-time model and its extensions are also being used for detailed scientific studies; examples of these show small day to day variability of VTEC without any change in solar activity and indication of the change in the shape of the VTEC diurnal curve with season. The present model will be used for further studies to derive the monthly average variation of the diurnal pattern and the relationship between VTEC peak amplitudes with changes in solar activity. The new information generated can be fed back to improve the real-time model so that eventually the dependence of such models on ground based network stations data can be minimised.

대양항로에서 장거리 공대지통신을 위한 VHF Relay Network

In oceanic flight routes, HF radio and satellite data links have been used for air-to-ground communication, but these systems have long propagation delay and low data throughput. In this paper, we propose a reliable system to overcome the weakness of current HF radio and satellite communication systems for oceanic aeronautical flight routes. The proposed scheme uses only one aeronautical VHF channel in multi-hop oceanic communication environments and supports a hybrid type of multiple access, which consists of random access and TDMA (Time Division Multiple Access) scheme. The proposed system improves performance on delay and throughput as an effective solution to communicate end-to-end on the oceanic flight routes and strengthens the reliability of oceanic aeronautical communication.

태양폭풍이 항행안전시설에 미치는 영향분석

The solar storm generated by solar activity can be impact on earth in various area. If solar storm impact on Navaids system, it will be a serious problem for aviation and human safety. The impact analysis of solar strom on Navaids system are performed in three area, ILS, GPS navigation and radio communication for aviation. Analysis result show that Instrument Landing System(LLZ, GP, MB) and Navaids system(VOR, DME, Radar) are not impacted by the solar storm, but GPS system is impacted by solar storm. Also analysis result show that VHF/UHF radio system are not impacted by solar storm, but HF radio system is impacted by solar storm.

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.

Storm sudden commencement and its effect on high‐latitude HF communication links

Following particle precipitation at high latitudes that occurs as a result of geomagnetic disturbances, the electron density of the E region of the ionosphere undergoes substantial variation. These variations modify the E layer propagation characteristics which adversely affect HF propagation paths both unexpectedly and in many cases for long periods of time. This paper presents two case studies of how the enhancement of E region electron density immediately following storm sudden commencement affects high‐latitude HF communications links in and through the auroral zone. Using data gathered from ionosondes, incoherent scatter radar and an oblique sounder, the Advanced Composition Explorer Satellite, and riometers and magnetometers, the physical effects of particle precipitation on the ionospheric E layer and the resulting effect on HF links is revealed. Both case studies show that besides the expected occurrence of severe short‐term absorption and the reduction in the critical frequency of the F layer caused by a redistribution of the electron density in the upper layers of the ionosphere, there is the likelihood a sporadic E layer will form and/or be enhanced because of significant and sustained particle precipitation. When the critical frequency of the sporadic E layer increases above the norm and in cases exceeds the critical frequency of the F layer, there are severe implications for many HF radio communication systems used at high latitudes unless corrective action is taken.

선박 애드 혹 네트워크를 위한 확장탐색구역 경로배정 프로토콜

Ships at sea cannot exchange data among them easily so far. Basically voice-oriented communication systems are the main methods, some of them utilize the HF radio systems at lower bit rates, and for higher bit rates, the Inmarsat or VSAT are adopted. None of them are used widely because of lower qualities and higher costs. There exist many technical and economical limits to have the Internet service just like on land such as the WWW service. In order to achieve the improved transmission rates of the maritime communication networks at farther sea, MANET(Mobile Ad Hoc Network) is one of the most practical models. In this paper, a new routing protocol named EZR (Expansive Search Zone Routing Protocol) is proposed, which is based on SANET (Ship Ad Hoc Network) model that has some different features from MANET and VANET (Vehicular Ad Hoc Network). The search zone for the shortest path is firstly found by EZR. If no path is searched in the zone, the zone is expanded according to the rule of EZR. The zone-expanding and path-searching procedures are repeated until the path is found out. The performance of EZR is evaluated and compared with LAR protocol which is one of the most typical routing protocols based on geographical information. The simulated results show that EZR is much better than LAR at sea environments in terms of routing success rate, route optimality, and a single index of performance combined the previous two metrics.

The IRI model residual difference and the new method of N(h)-profile determination

The effectiveness of performance of the HF radio communication systems depends in many aspects on the accuracy of description of ionospheric conditions. One of possibilities of such a description is to use the IRI model. In the paper it is shown that discrepancies of the model N(h)-profile shape and the real shape can make a contribution to errors of description of ionospheric conditions by means of the IRI model. A residual difference (RD) remains even after adjusting the IRI model to the real-time parameters of foF2 and hmF2. These differences are estimated for the N(h)-profiles calculated from ionograms by the traditional method POLAN and the new method NeXtYZ. Estimates are given for the influence of these differences on the prediction accuracy of such parameters as the maximum usable frequency and the distance D between transmitters and receivers. An attempt was made to decrease the residual difference along the HF path by means of an analytical function approximating RD.

Measurements of the Doppler and multipath spread of HF signals received over a path oriented along the midlatitude trough

The presence of the midlatitude trough can severely impact on HF radio systems since the electron density depletion within the trough reduces the maximum frequency which can be reflected by the ionosphere along the great circle path. Furthermore, the associated horizontal gradients in the electron density distribution frequently result in propagation well displaced from the great circle path. The signal characteristics associated with this type of propagation have been investigated for a 1400 km link oriented along the midlatitude trough between Sweden and the UK. As anticipated, the observed delay and Doppler spread characteristics are strongly dependent upon time of day and season since the trough is a nighttime feature which occurs predominantly during the winter. In particular, the Doppler spread is often large when great circle propagation has been suppressed and reflections are from the north of the great circle path (i.e., from the poleward wall of the trough or from gradients and/or irregularities associated with the auroral zone).

Performance comparison of spread-spectrum methods on an interference-limited HF channel

A severe problem with radio communication in the high-frequency range is the large amount of, typically narrowband, interfering signals from other users. A statistical description of the interfering signals is employed in evaluating different spread-spectrum HF radio systems. In particular, when a frequency-hopping (FH) and a direct-sequence (DS) system are compared, the FH system performs better than the DS system under the author's assumptions. The FH system is inherently well suited for the HF environment with its predominantly narrowband interfering signals. The interference rejection capability that the DS systems normally possess is not sufficient to handle the large dynamic range of the HF interfering power. Additional narrowband interference rejection would be required to create useful DS systems for the HF channel. Furthermore, the author demonstrates the dramatic gain connected with adaptive frequency-hopping, which uses an adaptively selected pool of the channels with least interference for the communication.

Performance prediction methods of HF radio systems

A survey of the historical development of methods for predicting the performance of ionospheric HF radio systems is presented, with special emphasis on modelling. The models considered are ionospheric characteristics and electron-density profile models, a propagation model, transmission loss and gain factors models, characteristics of radio noise models and a reliability model.

Observations of Doppler spreading on HF signals propagating over high latitude paths

The high latitude ionosphere forms a highly dynamic and disturbed medium which can severely degrade the performance of HF radio systems when the signals propagate through these regions. One important parameter is the Doppler frequency spreading imposed on the signal by the movement of electron density irregularities in the ionosphere at the reflection points. The magnitude of the Doppler spreading has been quantified in a series of experiments undertaken on a range of frequencies across the HF band over several high latitude paths. Two of these paths are considered in this paper, one of which (Clyde River – Alert, 1345 km) was contained entirely within the polar cap whilst the second (Clyde River – Prudhoe Bay, 2955 km) was sometimes entirely within the polar cap and at other times crossed the auroral oval. Results obtained over two one-month periods, one in summer (July/August 1988) and one in winter (January/February 1989), are presented.

A design for an automatic HF radio system

Microprocessor control systems, coding schemes, and modern communications equipment suggest new possibilities for the operation of HF radio systems. This paper describes a design concept for an automatic radio system, intended to overcome some of the traditional difficulties experienced with HF communications and to provide new capabilities including selective calling and automatic connectivity. The design incorporates a passive frequency selection technique using built‐in ionospheric prediction data and real time monitoring of channel interference levels.