HF radio wave propagation

geomagnetic index is used in programmes which use special models for high latitudes. Due to the variations and uncertainty in ionospheric conditions, prediction models can only give statistical information. ICEPAC is an enhanced IONCAP (Ionospheric Communications Analysis and Prediction) model developed by the Institute of Telecommunications Sciences (ITS) in Boulder, Colorado, during the 1970s [52]. ICEPAC is a full system performance model for HF radio communications circuits in the frequency range of 2 to 30 MHz. It was designed to predict HF sky wave system performance and analyse ionospheric parameters. ICEPAC was developed with a much more elaborate high-latitude ionospheric model called Ionospheric Conductivity and Electron Density (ICED), taking the geomagnetic Q index as an additional input parameter. The computer programme is an integrated system of subroutines designed to predict HF sky wave system performance and analyse ionospheric parameters. ICEPAC predictions require user-defined input data, such as the year, month, day, frequency of operation, type of antenna used, the transmitter power, the type of propagation prediction required and the man-made noise environment, among others [53]. The Australian Government IPS Radio and Space Services HF propagation prediction method is known as the Advanced Stand Alone Prediction System (ASAPS) and is able to predict sky wave radio communication conditions for both the HF and VHF radio spetra. ASAPS was developed by the IPS Radio and Space Services of the Australian Bureau of Meteorology, merges the features of the original IPS method with the ITU-R/ International Radio Consultative Committee (CCIR) models. Numerous graphic representations are based on this method according to the different needs of clients. The graphs have

Radio waves can travel long distances by multiple reflections off the ionosphere and off the earth with a high frequencies (HF, defined to be 3 - 30 mHz). HF ra- dio waves from the ground whose frequencies are under maximum usable fre- quency (MUF) travel further and further with each successive hop by the reflec- tions between the earth and the ionosphere again and again. And MUF has something to do with the season, time of day, and solar conditions. There is no reflection or refraction when the frequencies are over MUF. The characteristics of the reflecting surface determine the strength of the reflected wave and how far the signal will ultimately travel while maintaining useful signal integrity. The state of ocean also influences the attenuation of reflections. Ocean turbulence will affect the electromagnetic gradient of seawater, alter the local permittivity How to cite this paper: Chen, Y.R., Han,

The Usable Frequency Range In radio communications, not all HF waves are reflected by the ionosphere; there are upper and lower frequency bounds for communications between two terminals. If the frequency is too high, the wave will pass straight through the ionosphere. If it is too low, the strength of the signal will be very low due to absorption in the D region. The definition of the frequency to be used for radio communication is an important parameter for healthy of propagation. For this, the Maximum Usable Frequency (MUF), and the Lowest Usable Frequency (LUF) are determined. Frequencies over MUF penetrate the ionosphere shooting right through the ionosphere and going out into space, whereas frequencies below MUF are reflected. LUF is the lowest frequency that is completely absorbed in the D layer. To conduct good communication, a frequency, calculated as MUF, should be used. This frequency may be lower at

There are at least two possible mechanisms that could lead to a significant signal strength reduction (attenuation) in bushfire environments. They are signal refraction due to thermal bubble and ionization-induced signal absorption in the plume. Electrons, which result from thermal ionization of potassium in the fire, transfer energy from the incident radio wave to the fire plume through collision with inherent neutral particles. The transfer of energy can significantly attenuate and induce a phase shift on radio wave signals. Experimental work carried out in the project suggest that radio wave attenuation is significantly higher at UHF and X-Band frequencies than at HF. Field radio wave propagation measurements at 1.50 m above the seat of a moderate intensity grassfire revealed that 30 MHz signals can be attenuated by up to 0.03 dB/m while 151.3 MHz signals were attenuated by up to 0.05 dB/m. An intense cane fire attenuated 151.3 MHz signals by 0.05 dB/m. The attenuation effect was observed to increase when X-band (10.0 -12.5 GHz) signals were considered. Attenuation coefficients up to 4.45 dB/m were measured.

turn derived within the WKB or geometrical optics ap- proximation. However, it is impossible to obtain the E → value in the vicinity of the reflection (conversion) point, where the WKB approximation breaks down (Ginzburg, 1970). A purely numerical simulation method for obtaining the variation of the pump-wave E → in the whole reflection region is used by Gondarenko et al. 2004. In addition, the ray tracing method proposed by Field et al. 1990 and Hinkel et al. 1993 yields the spatial distribution of the pump-wave → E by accurately calculating the phase of the pump-wave propagation path. An ingenious analyt- ical method devised by Lundborg and Thide 1985, 1986 is used to calculate the variation of the characteristic- wave E → near the reflection region, but only ordinary (O)-mode waves are considered. As regards Chinese scholars, the empirical model is mostly used directly, to estimate the spatial distributions of the pump-wave E → ; however, these estimates are accurate to within an order of magnitude only (Huang and Gu, 2003; Hao et al. 2013). Of course, purely numerical methods can obtain the variation of the pump-wave → E ; however, the numerical models are very complex and the computa- tional requirements are high. In addition, analytical methods always provide more information about the solution than pure numbers, and analytic formulas are very quickly evaluated, even on a moderately sized desktop computer.

The interaction of large-amplitude high-frequency (HF) radio waves with the ionospheric plasma in the vici- nity of the dip equator is signi fi cantly different than the well-studied interactions in the polar and middle lati- tude regions. Previous theoretical study [Erukhimov et al., 1997] proposed a variety of effects including the creation of quasi-periodic structures with vertical periodicity of approximately half the wavelength of the electromagnetic (EM) wave and extending horizontally along the magnetic fi eld lines due to Ohmic heating of the plasma, as well as creation of a virtual antenna at ULF/ELF/VLF frequencies by modulation of the D/E conductivity of the equatorial electrojet similar to the modulation of the polar electrojet in the auroral region [Rietveld et al., 1984, 1987, 1989; Papadopoulos et al., 1990, 2005; Moore, 2007; Payne et al., 2007]. Advantages of the equatorial over the polar electrojet modulation were noted by Papadopoulos et al. [2005], while Erukhimov et al. [1997] emphasized the excitation of low-frequency Alfvén waves in the 1 Hz frequency range. EM waves exceeding a threshold amplitude could also drive arti fi cial ionospheric turbulence (AIT) by the nonlinear interaction of ordinary (O) mode wave with the plasma electrons. In this case, since the O mode has its electric fi eld along the ambient magnetic fi eld lines when it reaches the critical layer, it could excite AIT associated with large amplitude Langmuir waves and ion acoustic waves propagating along the magnetic fi eld. Experiments at the Large Plasma Device (LAPD) at University of California, Los Angeles (UCLA) [Van Compernolle et al., 2006; Wang et al., 2016] have also shown the formation of suprathermal electrons accom- panied by the excitation of Alfvén waves when large-amplitude microwaves are injected into the plasma perpendicular to the magnetic fi eld. Particle-in-cell simulations [Tsung et al., 2007] and subsequent laboratory experiments indicate that accelerated

Propagation measurement data at radio wave (HF-VHF) frequencies through fire are scarce and that which is available lacks precision. It is also the purpose of the study to produce attenuation and phase measurement data at these frequencies. The field and laboratory measurements were carried out using a Radio Wave Interferometer (RWI) and Vector Network Analyzer (VNA - HP 8277C). RWI uses the same principles as Microwave interferometer (MWI) except that RWI works at radio frequencies. Electron density and momentum transfer collision frequency in moderate intensity bushfire plumes were estimated from the attenuation and phase shift measurements.

o At MF and in the lower HF bands, aerials tend to be close to the ground (in terms of wavelength). Hence the direct wave and reflected wave tend to cancel each other out (there is a 180 degree phase shift on reflection). This means that only the surface wave remains.

This chapter is about the introduction of Indoor Radio Propagation which is already state a few subtitle that we must know in this project. The basic radio propagation was already explained and clearly about specification for this project. Then, know about the multipath that occurred in the wireless transmission. The phenomenon of reflection, diffraction and scattering all give rise to additional radio propagation paths beyond the direct optical "line of sight" path between the radio transmitter and receiver.

With the development of 5G (the fifth generation), the current wireless communication spectrum resources are increasingly scarce. Millimeter waves have rich spectrum resources and become the research hotspot and development trend of the future 5G system [1]. By analyzing and processing the actual measured data, the propagation model similar to the actual channel is established to qualitatively study and model the millimeter wave channel [2]. It is especially important to find a suitable propagation model for indoor signal coverage problems.

The di ff erent spectral aspects of the radio sparks can be ex- plained by the properties of the wave fronts, which may have di ff erent temporal and spatial extents, similar to the snapshots of the fast magnetoacoustic waves generated by geometrical disper- sion in a plasma funnel in Pascoe et al. (2013). The first spark ex- hibits a frequency drift, which can be explained by a broad wave front, such as the one indicated in Fig. 2. Additionally, from Fig. 4 panel a) it can be seen that E1 is more temporally broad than the following peaks, which could give rise to the drift seen in R1. From the frequency range each spark covers the vertical extent of the emission region for each was calculated, giving L = [29, 24, 26, 32] Mm for R1 - R4. These values support our interpretation that the emission is generated in a localized region correspond- ing to a feature of finite vertical width, such as the expanding front ahead of the CME.

This section briefly outlines the experimental set up used for our propagation measurement. All the experiments have been carried out at Non-Line-of-Sight (NLOS) environment of complex building along all L-shape corridors in main building of Mandalay Technology University, the Republic of the Union of Myanmar. In all measurements, TP-Link TL-WR1043N router with 8dbi omnidirectional antenna was used for wireless transmitter and LAPTOP (3dBi) with Microsoft WINDOWS 7 operating system was used for receiver. To survey received signal strength, the wireless signal analyzer software called inSSIDer was installed in this laptop. Carrier frequency was 2.4GHz with 20dBm transmitted power. At first, TP-Link TL-WR1043N router is located in a fixed centre position of corridor (4). The placement of transmitter was constant, when the heights of transmitter and that of receiver were equal or not equal. The height of receiver was also constant with 1.1m, when the height of transmitter was 1.1m or 1.6m. There are two positions of receiver’s placement when conducting all experiments. The first placement of receiver is at the centre of each corridor and the other is 1 meter from the side wall of each corridor to the centre of that corridor. All experimental points are marks as 1 meter from the transmitter along L-shape form of hallway and moved the receiver to each experimental point along the corridor to the end of it. In all experiments, the receiver is rotated to four sides of it at each point in order to get the average values of received signal strength. And then, all experimental data were used to draw received signal power with the help of Matlab programming language.

Figure-5b shows the transmission respond of microwave signal through glass coated with SnO2 thin film deposited at various O2 flow ratios.. The rf discharge power was fixed at 225 W.[r]

With the advent of microcellular radio networks likely to be employed in third-generation mobile communication systems there is increased interest in propagation models that are able to provide location-specific predictions of channel parameters [4]. Many vegetation models have since been developed, but some of these models are range and frequencies-specific, hence do not perform well in all scenarios. In this paper, measurement, modeling and validation of existing models on the effect of inhomogeneous vegetation density on UHF radio-wave propagation through a long forested channel at frequency of 1835 MHz are reported.

Commercial stations operate with very tight frequency tolerance so your SSB radio must match that frequency accuracy. Ideally, your radio should have a digital readout which displays Kilohertz to two digits, 12527.00 kHz, not 12527.0 kHz. Most modern maritime and amateur SSB radios have these features, however there are some which do not. If you have an older SSB radio that does not have a digital dial display or has low dial resolution, then it will be difficult to accurately tune shore stations. If your transmitter cannot be set on frequency accurately, exhibits drift characteristics, or is slow when changing between transmit and receive, you'll have

In this paper, a novel wavelet-Galerkin method is presented for the numerical solution of two dimensional parabolic equation. A new ‘fictitious domain method’ is also introduced for parabolic wave equation to incorporate the impedance boundary conditions. A brief discussion on the behavior of radiowave propagation in troposphere is also provided. At the end, results are compared with those from AREPS for both environment conditions — standard and ducting. The results show that the proposed algorithm is nearly as good as AREPS and it can be a better alternative to other well-known methods. From the simulation results, it is also found that the grid size for height and range operator is chosen carefully to make WGM computationally efficient. Smaller grid size is required for higher frequencies due to which WGM cannot save significant computation cost, relative to the AREPS. In spite of this, wavelet methods still have special properties like multi-resolution analysis and exact solution of connection coefficient which make them superior to other conventional methods and allow to provide higher accurate solutions.

Abstract—Rigorous electrodynamic analysis is proposed to estimate the surface current density on the perfectly conducting chiral elements in the diffraction problems. It is reduced to the solution of the integral singular equations. The diffraction of plane electromagnetic wave on the cylindrical open ring is considered as an example.

We are aiming to develop new sensing systems exploiting radio wave propagation characteristics such as localization for mobile objects including sensors and persons, and also for reso[r]

Abstract— Here the model of anisotropic elastic medium is considered. Law of wave propagation for such mediums is more difficult than for isotropic medium and stress-strain state essentially depends from degree of its anisotropy. For the equations of motion of such media, fundamental solutions that correspond to the action of concentrated forces are constructed. The pictures of wave fronts and the amplitudes of displacements for orthotropic media under the action of a concentrated impulse force are presented. The existence of lacunae for strongly anisotropic media is shown.

Bipolar disposable Ag/Ag-Cl surface electrodes (ES40076 Kendall, Mansfield, MA) were used to monitor the activation levels of the tibialis anterior (TA) and lateral gastrocnemius (LG). Following shaving and cleaning of the skin with rubbing alcohol, two electrodes were placed over the belly of each muscle, with an inter-electrode spacing of 2 cm (Figure 20). Electromyographic data for both muscles were full-wave rectified and filtered using a second order dual pass Butterworth filter with a cut-off frequency of 1 .5 Hz. Data were then normalized to the maximum voluntary exertion (MVE) that the participant was able to produce for each muscle (see section 3.1.2.4). During the experimental impact trials, the participant was provided with real-time visual feedback regarding the activation of the TA and LG on a computer monitor positioned in their line of sight, and was asked to maintain a constant activation level throughout the duration of the impact (see section 3.1.2.4).