Showing papers on "Radio wave published in 2000"

Radio sources in low-luminosity active galactic nuclei. ii. vlbi detections of compact radio cores and jets in a sample of liners

Abstract: We have used the VLBA at 5 GHz to observe all galaxies with nuclear radio flux densities above 3.5 mJy found in a VLA survey at 15 GHz of a sample of nearby LINER galaxies. All galaxies were detected revealing high brightness temperature (Tb ∼ 10 8 K) radio sources. Free-free emission is unlikely since it greatly overpredicts the soft X-ray luminosities. We infer the presence of AGN-like, non-thermal radio emission most likely powered by under-fed black holes. Together with our VLA sample we estimate from our observations that at least half of LINER galaxies host genuine AGN. We find no evidence for highly inverted radio cores as predicted in the ADAF model: the (non-simultaneous) spectral indices are on average around α = 0.0. In the two brightest sources we detect some extended emission, which appears to originate in jets in at least one of these galaxies. Together with the spectral indices this suggests that the nuclear emission at centimeter radio waves is largely dominated by emission from radio jets, very similar to the situation in more luminous AGN. The energy released in these jets could be a significant fraction of the energy budget in the accretion flow. Subject headings: galaxies: active — galaxies: jets — galaxies: nuclei — galaxies: structure — galaxies: Seyferts — radio continuum: galaxies

Radio Sources in Low-Luminosity Active Galactic Nuclei. II. Very Long Baseline Interferometry Detections of Compact Radio Cores and Jets in a Sample of LINERs

Abstract: We have used the VLBA at 5 GHz to observe all galaxies with nuclear radio flux densities above 3.5 mJy found in a VLA survey at 15 GHz of a sample of nearby LINER galaxies. All galaxies were detected revealing high brightness temperature (Tb 108 K) radio sources. Free-free emission is unlikely since it greatly overpredicts the soft X-ray luminosities. We infer the presence of active galactic nucleus (AGN)-like, nonthermal radio emission most likely powered by underfed black holes. Together with our VLA sample we estimate from our observations that at least one-half of LINER galaxies host genuine AGNs. We find no evidence for highly inverted radio cores as predicted in the advection-dominated accretion flow model: the (nonsimultaneous) spectral indices are on average around α = 0.0. In the two brightest sources we detect some extended emission, which appears to originate in jets in at least one of these galaxies. Together with the spectral indices this suggests that the nuclear emission at centimeter radio waves is largely dominated by emission from radio jets, very similar to the situation in more luminous AGNs. The energy released in these jets could be a significant fraction of the energy budget in the accretion flow.

Diffusion Waves and their Uses

Abstract: The concept of waves is an integral part of our scientific culture and has nourished physicists, pure and applied alike, for centuries. Many important discoveries in physics, including quantum mechanics, have involved wave phenomena. The wave concept owes some of its scientific success to its mathematical tractability. Linear wave equations—the sort that describe the transmission of sound and radio waves through air—contain a nonzero second‐order time derivative, which gives rise mathematically to the rich and familiar array of properties we associate with waves, such as wavefront propagation, reflection, and refraction.

Efficient ray-tracing acceleration techniques for radio propagation modeling

Abstract: Ray-tracing and uniform theory of diffraction techniques are already widely applied to site-specific radio propagation modeling for wireless applications. Software tools using such techniques may take considerable computation time in the analysis of the propagation conditions in a given environment even for a short mobile terminal route. Efficient acceleration techniques are required to make such analysis tools practical for the design of modern radio systems. To reduce computation time, ray-tracing routines must be applied only to those areas where rays are likely to exist. This is achieved by using ray-path search algorithms prior to performing any actual ray tracing. An efficient ray-path search algorithm is presented. First, a two-dimensional version is described, which is valid for indoor and microcell studies. Then, an extension to the three-dimensional case is explained in detail. Finally, the software tool Radio Tracer using such techniques is briefly described, and some comparisons between experimental results and computed predictions for indoor and outdoor scenarios are shown.

Mobile body discrimination apparatus for rapidly acquiring respective data sets transmitted through modulation of reflected radio waves by transponders which are within a communication region of an interrogator apparatus

Abstract: In a mobile body discrimination apparatus having an interrogator apparatus (1) and a plurality of transponders (20) each capable of transmitting information to the interrogator apparatus by modulation of radio waves that are reflected from a transponder antenna (24), which can be attached to respective articles, store data concering the articles, and transmit the data to the interrogator apparatus in response to a command signal transmitted while the transponder traverses a communication region of an antenna of the interrogator apparatus, each transponder is configured to begin sending such response data after a randomly determined time interval following reception of the command signal, thereby reducing the probability of data conflict when plural transponders are within the communication region. In addition, radio waves from a second antenna (10) of the interrogator apparatus are directed into that communication region in the intervals between transmissions of the command signal, thereby increasing the power level of radio waves that are reflected by a transponder antenna or used by a rectifier circuit (21) to supply power for operating the transponder circuits.

Signal processing for object detection system

Abstract: Methods and apparatus for detecting objects. In one embodiment, a person entering a secured or “Safe Zone™” is illuminated with low-power polarized radio waves. Differently polarized waves which are reflected back from the person are collected and measured. In a preferred embodiment, concealed weapons are detected by calculating the difference of a pair of differences (Delta A and B) of different polarized reflected energy (upper and lower curves in the two graphs) in the time domain, and by using signal processing methods and apparatus to improve the reliability of the detection process.

Propagation prediction techniques and antenna modeling (150 to 1705 kHz) for intelligent transportation systems (ITS) broadcast applications

Abstract: This paper discusses the basic aspects of radio-wave propagation and antenna modeling at 150 to 1705 kHz The paper contains descriptions of both sky-wave and ground-wave propagation-prediction models, in addition to the methodology used to analyze antennas that operate in this band A method of calculating and normalizing antenna gain for system computations is also discussed The sky-wave models described in this paper are valid from 150 to 1705 kHz The ground-wave models described in this paper are valid from 10 kHz to 30 MHz The propagation of radio waves from 150 to 1705 kHz includes both a ground wave and a sky wave, and is quite different from propagation at any other frequency The methods used for antenna modeling and analysis in this band are also quite unlike those in other bands The AM broadcast band of 535 to 1605 kHz is planned to be used in the advanced traveler information systems (ATIS) of intelligent transportation systems (ITS), to provide information such as road conditions, road hazards, weather, and incident reporting for rural travelers The band of frequencies from 285 to 325 kHz is presently being used in another application of ITS, called the Differential Global Positioning System (DGPS), which will be used for precision location of vehicles The propagation-prediction models and antenna-analysis methods described here can be used for designing systems and making performance predictions for both of these ITS applications, or for any other systems that operate in this band of frequencies from 150 to 1705 kHz Some examples of comparisons of measured and predicted data are also presented A computer program that includes all of these propagation-prediction models and antenna-modeling techniques was used

Radio communication system for vehicle

Abstract: A radio communication system for a vehicle which allows communication not only between a driver and a passenger of one vehicle but also with a driver or a passenger of another vehicle without increasing the scale of a radio communication apparatus to be mounted on a helmet. A radio wave signaled from a radio wave transmitter-receiver of a driver or a passenger of a vehicle is received by a repeating apparatus of the self-vehicle and amplified by and re-signaled from the repeating apparatus. The radio wave signaled from the repeating apparatus is received by a radio wave transmitter-receiver of a driver or a passenger of another vehicle and reproduced by a speaker. A radio wave signaled from the radio wave transmitter-receiver of the driver or a passenger of the vehicle is received by a repeating apparatus of the self-vehicle and amplified by and re-signaled from the repeating apparatus. The radio wave signaled from the repeating apparatus is received by the radio wave transmitter-receiver of a driver or a passenger of the vehicle and reproduced by a speaker.

Fluctuations in the Radio Background from Intergalactic Synchrotron Emission

Abstract: The shocks produced in the intergalactic medium during large-scale structure formation accelerate a population of highly relativistic electrons that emit synchrotron radiation due to intergalactic magnetic fields. In a previous paper we have shown that these electrons cool primarily by inverse Compton scattering of the microwave background photons and can thereby produce the observed intensity and spectrum of the diffuse γ-ray background. Here we calculate the intensity and angular fluctuations of the radio synchrotron background that results from the same high-energy electrons as well as the expected angular fluctuations in the γ-ray background. On angular scales smaller than a degree, the predicted fluctuations in the microwave background temperature are of order 40 μK(ξB/0.01)(ν/10 GHz)-3, where ξB is the magnetic fraction of the postshock energy density. This foreground might have already dominated the anisotropy signal detected in existing low-frequency cosmic microwave background experiments and can be identified with confidence through multifrequency observations. Detection of the synchrotron fluctuations would allow us to determine the strength of the intergalactic magnetic field. We predict a strong correlation between high-resolution maps taken at low-frequency radio waves and at high-energy γ-rays. Young X-ray clusters may also appear as radio or γ-ray clusters. The detailed study of this correlation will become easily accessible with the future launch of the Gamma-Ray Large-Area Space Telescope.

Elastic Wave Propagation

Abstract: When a localized disturbance is applied suddenly into a medium, it will propagate to other parts of this medium. The local excitation is not detected at other positions of the medium instantaneously, as some time would be necessary for the disturbance to propagate from its source to other parts of the medium. This simple fact constitutes a general basis for the interesting subject of “wave propagation”. Well-cited examples of wave propagation in different media include, for instance, the transmission of sound in air, the propagation of a seismic disturbance in the earth, the transmission of radio waves, among others. In the particular case, when the suddenly applied disturbance is mechanical, e.g., an impact force, the resulting waves in the medium are due to mechanical stress effects and, thus, these waves are referred to as “mechanical stress waves”, or simply “stress waves”. Our attention in this text is restricted to the study of the propagation of stress waves in engineering materials.

Inversions of radio occultation amplitude data

Abstract: Radio occultation remote sensing of the Earth's atmosphere consists of satellite-to-satellite observations of phase and amplitude of radio waves that propagate through the atmosphere. The observed excess phase along with the positions and velocities of the satellites are inverted into bending angle as a function of impact parameter and then into vertical profiles of refractivity, pressure, and temperature in the neutral atmosphere, or into electron density in the ionosphere. The retrieved profiles are assigned to the perigee points of the sounding rays. Amplitude data are normally not used, except when solving diffraction back propagation problems. In this paper a simple method to utilize amplitude radio occultation data is discussed. Equations based on geometric optics are considered for the inversion of an amplitude into bending angle. These inversions do not require high coherence of radio waves or precise orbit determination, as with phase inversions, but they do require precise calibration of the amplitude. Even though amplitude inversions are not so precise as phase inversions, they may still be useful for a number of applications. When compared to phase inversions they allow the optimization of the filter bandwidth for phase inversions, the detection of multipath propagation, and the localization of electron density irregularities in the ionosphere. These applications are demonstrated by processing of the Global Positioning System/Meteorology (GPS/MET) radio-occultation data collected onboard the satellite Microlab-1.

A possible mechanism for echo striation generation of radar backscatter from midlatitude sporadic E

Abstract: The morphological resemblance is described between the quasi-periodic scintillations of VHF radio wave transmissions from a satellite and the 46.5-MHz radar backscatters of the middle and upper atmosphere (MU) radar radio waves, which are both associated with ionospheric irregularities in the sporadic E layer. Because these observation techniques are sensitive to different wavelengths of irregularities, the resemblance may be caused by coexisting irregularities. That is, radio wave scintillations reveal medium-scale density-enhanced regions with a specific scale length of several hundred meters in which small-scale irregularities are embedded. The MU radar echoes may reveal backscatter signals from small-scale irregularities. A periodic structure on a range-time-intensity (RTI) map reflected the spatial structure of the medium-scale density-enhanced regions. A model is proposed to explain the striations on the RTI map, which extend up to heights of several tens of kilometers even though sporadic E layers are usually thin.

Optical remote sensing of the thermosphere with HF pumped artificial airglow

Abstract: Optical emissions excited by high-power radio waves in the ionosphere can be used to measure a wide variety of parameters in the thermosphere. Powerful high-frequency (HF) radio waves produce energetic electrons in the region where the waves reflect in the F region. These hot or suprathermal electrons collide with atomic oxygen atoms to produce localized regions of metastable O(1D) and O(1S) atoms. These metastables subsequently radiate 630.0 and 557.7 nm, respectively, to produce clouds of HF pumped artificial airglow (HPAA). The shapes of the HPAA clouds are determined by the structure of large-scale (≈10 km) plasma irregularities that occur naturally or that develop during ionospheric heating. When the HF wave is operated continuously, the motion of the airglow clouds follows the E × B drift of the plasma. When the HF wave is turned off, the airglow clouds decay by collisional quenching and radiation, expand by neutral diffusion, and drift in response to neutral winds. Images of HPAA clouds, obtained using both continuous and stepped radio wave transmissions, are processed to yield the electric fields, neutral wind vectors, and diffusion coefficients in the upper atmosphere. This technique is illustrated using data that were obtained in March 1993 and 1995 at the ionospheric modification facility near Nizhny Novgorod, Russia. Analysis of HPAA clouds yields zonal plasma drifts of 70 m s−1 eastward at night. On the basis of artificial airglow from energetic electrons generated at 260 km the zonal neutral wind speed was estimated to be 96 m s−1 and the O(1D) diffusion coefficient was determined to be between 0.8 and 1.4 × 1011 cm2 s−1. The quenched lifetime of the O(1D) was determined to be 29.4 s. The diffusion and quenching rates are directly related to the atomic and molecular concentrations in the thermosphere. Improvements in the remote-sensing technique may be obtained if the intensity of the artificial airglow emissions is increased. High-power radio transmissions employing pulse sequences and tuning near electron cyclotron harmonics were attempted to increase the optical emissions. Both of these, however, produced reduced intensity, and consequently, continuous transmission at frequencies away from electron gyro harmonics is the preferred heating regime.

Radio wave emissions due to gravitational radiation

Abstract: We consider the interaction of a weak gravitational wave with electromagnetic fields in a thin plasma on a Minkowski background spacetime using the 1+3 orthonormal frame formalism. Because gravitational and electromagnetic waves satisfy the same dispersion relation, electromagnetic waves can be effectively generated as a result of this interaction. In the case of the interaction with a static magnetic field, the amplitude of the electromagnetic waves depends on the size of the excitation region in which the magnetic field is contained. It is argued that because of the presence of a plasma this process can also lead to the generation of higher harmonics of the original mode. Estimates are given for this effect in the case of a binary pulsar and a cold electron plasma. It is found that the emitted radiation will lie in the radio frequency band. We also speculate on the possible relevance of this process on situations in cosmology, in particular, whether this could be used to constrain primordial magnetic fields.

First EISCAT measurement of electron-gas temperature in the artificially heated D-region ionosphere

Abstract: . The ionospheric electron gas can be heated artificially by a powerful radio wave. According to our modeling, the maximum effect of this heating occurs in the D-region where the electron temperature can increase by a factor of ten. Ionospheric plasma parameters such as Ne, Te and Ti are measured by EISCAT incoherent scatter radar on a routine basis. However, in the D-region the incoherent scatter echo is very weak because of the low electron density. Moreover, the incoherent scatter spectrum from the D-region is of Lorentzian shape which gives less information than the spectrum from the E- and F-regions. These make EISCAT measurements in the D-region difficult. A combined EISCAT VHF-radar and heating experiment was carried out in November 1998 with the aim to measure the electron temperature increase due to heating. In the experiment the heater was switched on/off at 5 minute intervals and the integration time of the radar was chosen synchronously with the heating cycle. A systematic difference in the measured autocorrelation functions was found between heated and unheated periods. Key words: Ionosphere (active experiments; plasma temperature and density; wave propagation)

FAST observations of ULF waves injected into the magnetosphere by means of modulated RF heating of the auroral electrojet

Abstract: Results are reported from an experiment in which the HF high power facility at Tromso was utilised to inject artificial ULF waves into the magnetosphere by means of modulated heating of the auroral electrojet. Local electric field oscillations associated with the artificially stimulated ULF waves were detected on board the FAST spacecraft, at an altitude of 2550 km. In addition, a modulated downward flux of electrons was also detected. The artificially excited waves, together with these energised downward electrons, were observed in a narrow region only a few tens of km across the geomagnetic field, which mapped down the geomagnetic field line to the heated volume in the ionosphere. Furthermore, the downward flux exhibited energy dispersion in a manner that was consistent with the artificially excited waves having followed the geomagnetic field line out beyond the spacecraft, where they appear to have stimulated electron precipitation back down the field line.

Radio equipment and radio network

Abstract: PROBLEM TO BE SOLVED: To reduce interference in a radio LAN and to increase the number of radio LANs to be contained in the fixed number of radio channels. SOLUTION: An optimal channel is decided by judging radio wave states of all the usable radio channels, in the case of startup and the optimal channel also for changes of surrounding state is decided by periodically stopping the transmission of the present station by a master station and distributively monitoring neighboring radio wave state by a slave station in present radio network. Furthermore, in the case of shortage of channels, storage of more radio networks is enabled with fewer radio channels by sharing and using the channel being used by other network by mutually mediating it. COPYRIGHT: (C)2002,JPO

Radio communication system

Abstract: PROBLEM TO BE SOLVED: To perform sure communication at all times without making the communication of a first radio station and a second radio station receive the interference of radio waves from a third radio station. SOLUTION: This system is composed of a radio POS base station 51 and a radio POS terminal station 54 for performing radio communication with each other and a radio tag detector 57 for performing the radio communication with a radio tag 58 by using the almost same frequency as the frequency used by the respective radio stations. The terminal station is provided with a state signal generation part 78 for generating state signals for indicating that it is during reception at the time of receiving information signals addressed to the present station from the base station and power line carrier communication equipment 77 for transmitting the state signals generated by the state signal generation part through a power source line 71 to the radio tag detector. The radio tag detector is provided with the power line carrier communication equipment 86 for receiving the state signals from the terminal station and a state signal storage part 88 for storing the received state signals. While the storage part stores and holds the state signals, the transmission of interrogation waves to the radio tag is inhibited.

Radio Astronomical Polarimetry and the Lorentz Group

Abstract: In radio astronomy, the polarimetric properties of radiation are often modified during propagation and reception. Effects such as Faraday rotation, receiver cross talk, and differential amplification act to change the state of polarized radiation. A general description of such transformations is useful for the investigation of these effects and for the interpretation and calibration of polarimetric observations. Such a description is provided by the Lorentz group, which is intimately related to the transformation properties of polarized radiation. In this paper, the transformations that commonly arise in radio astronomy are analyzed in the context of this group. This analysis is then used to construct a model for the propagation and reception of radio waves. The implications of this model for radio astronomical polarimetry are discussed.

Discrete electrostatic eigenmodes associated with ionospheric density structure: Generation of auroral roar fine frequency structure

Abstract: Radio emissions emanating from the Earth and other planets are often characterized by discrete frequency structures. For example, recent ground-based observations of auroral roar, an auroral radio emission which occurs near the second and third harmonic of the electron cyclotron frequency, show that it consists of fine frequency structure similar to that of auroral kilometric radiation and other planetary radio emissions. These auroral roar fine structures, sometimes as narrow as a few hertz, often occur in multiplets separated by the order of < 1 kHz which drift up and down in frequency. Theoretical and experimental efforts to explain the generation of auroral roar suggest that in the source region near the F region peak, the quasi-electrostatic Z mode (or upper-hybrid) waves are first excited, partly converted to free-space radio waves and subsequently observed on the ground. Using WKB-type calculations of the wave mechanics of upper-hybrid modes in a cylindrical field-aligned density structure, we show that discrete frequency eigenmodes are a natural consequence of such density structures. Discrete eigenmodes can exist within density enhancements but not within depletions. Cylindrical field-aligned structures the order of 100 m to several kilometers diameter result in eigenmodes spaced by a few hundred hertz as observed for auroral roar. Since structure of this scale size often occurs in the Earth's auroral ionosphere at F region altitudes, it seems possible that the observed auroral roar fine structure results from this mechanism.

Radio control system and radio control method

Abstract: The same ID is assigned to a pair of a plurality of transmitters 100 and RC cars 200 . The transmitter 100 transmits a radio wave signal embodying command signal defining movement of a target RC car 200 , and ID indicating the target RC car 200 . The RC car 200 receives the radio wave signal, and is driven in accordance with the command signal embodied in the received radio wave signal when the ID in the received radio wave signal coincides with the receiver's ID.

Method for locating radio mobile terminal

Abstract: PROBLEM TO BE SOLVED: To obtain a method for locating a radio mobile terminal in which the accuracy of location is enhanced. SOLUTION: Field strength E(i) of each radio wave delivered from a plurality of base stations is measured at the position of a radio mobile terminal and the positional coordinates P of the radio mobile terminal is determined temporarily. Distance between the positional coordinate of each of the plurality of base stations and the positional coordinates of the radio mobile terminal is then calculated as a first distance Rc(i) and at least one coefficient K included in an expression representing the relation between the field strength and the distance is calculated based on the field strength E(i) and the first distance Rc(i). The field strength E(i) and the calculated coefficient K are substituted into the relation and the distance between the radio mobile terminal and each of the plurality of base stations is calculated as a second distance Re(i). Subsequently, the positional coordinate of the radio mobile terminal is corrected utilizing the first distance Rc(i) and the second distance Re(i) thus obtaining the positional coordinate where error is suppressed. COPYRIGHT: (C)2002,JPO

Measurements of the propagation of UHF radio waves on an underground railway train

Abstract: Measurements of the natural propagation of UHF radio waves on an underground train are reported. Of prime interest are the natural propagation attenuation and the median signal level behavior. The propagation attenuation rates or the median signal level behaviors are found to correlate with the train carriages and frequency. On the front carriage, the propagation attenuation rate is 54 dB/100 m at 465 MHz and reduced to 21 dB/100 m at 820 MHz. However, on the rear carriage, it becomes 14.8 dB/100 m at 465 MHz and 7.8 dB/100 m at 820 MHz. It is shown that higher frequency is beneficial to the natural propagation and the train body greatly affects the natural propagation. Furthermore, the values of the path loss exponent are also given.

Radio Plasma Imager Simulations and Measurements

Abstract: The Radio Plasma Imager (RPI) will be the first-of-its kind instrument designed to use radio wave sounding techniques to perform repetitive remote sensing measurements of electron number density (N e ) structures and the dynamics of the magnetosphere and plasmasphere. RPI will fly on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission to be launched early in the year 2000. The design of the RPI is based on recent advances in radio transmitter and receiver design and modern digital processing techniques perfected for ground-based ionospheric sounding over the last two decades. Free-space electromagnetic waves transmitted by the RPI located in the low-density magnetospheric cavity will be reflected at distant plasma cutoffs. The location and characteristics of the plasma at those remote reflection points can then be derived from measurements of the echo amplitude, phase, delay time, frequency, polarization, Doppler shift, and echo direction. The 500 m tip-to-tip X and Y (spin plane) antennas and 20 m Z axis antenna on RPI will be used to measures echoes coming from distances of several R E RPI will operate at frequencies between 3 kHz to 3 MHz and will provide quantitative N e values from 10-1 to 105 cm-3. Ray tracing calculations, combined with specific radio imager instrument characteristics, enables simulations of RPI measurements. These simulations have been performed throughout an IMAGE orbit and under different model magnetospheric conditions. They dramatically show that radio sounding can be used quite successfully to measure a wealth of magnetospheric phenomena such as magnetopause boundary motions and plasmapause dynamics. The radio imaging technique will provide a truly exciting opportunity to study global magnetospheric dynamics in a way that was never before possible.

An empirical study of radio propagation aboard naval vessels

Abstract: Most existing studies of indoor radio wave propagation have addressed operations in common commercial environments such as warehouses, office buildings and factories. These studies show typical path loss gradients ranging from 3-5, and rms delay spreads ranging from 10-40 nanoseconds. This paper reports the results of research conducted to characterize microwave radio propagation aboard Navy ships. Because of its principally steel construction, the ship environment displays significantly different characteristics from commercial environments. In particular, rms delay spreads ranging between 70 and 90 nanoseconds are common. Likewise, path loss gradients are observed to range from slightly greater than inverse square to smaller than unity. These effects of path loss and delay spread are found to be independent of frequency, over the range from 800 MHz to 2.6 GHz.

Electromagnetic wave lane marker, device for detecting electromagnetic wave lane marker, and traffic system

Abstract: The level of the electromagnetic waves transmitted by resonance of an electric resonator is only one hundredth that of calling radio waves of the detector. Furthermore, when an IC is mounted on the electric resonator and a modulated information code is superposed, the level of the superimposed electromagnetic waves further declines. As a result, sufficient detection directivity and detection distance could not be obtained. To address these problems, the present invention stores a cyclic coil and a capacitor used to cause an electric resonance in response to the first frequency in a sealed non-magnetic container to prevent degradation.

Vehicle radio having RDS presets and method therefor

Abstract: The present invention provides for an easy-to-use radio that enables quick selection of radio station channels according to program type. The radio includes a receiver for receiving radio wave signals on radio station signal channels having radio data information, and has a tuner tuneable to one or more of the radio station signal channels. The radio has a processor for receiving and deciphering the radio data information and memory for storing a plurality of programmable preset channels according to a program type indicative of the type of the radio station broadcast. The radio further has a user input for selecting one of the programmable presets and for further selecting one of the preset radio station signal channels based on the selected preset.

Radio having adjustable seek sensitivity based on average signal strength and method therefor

Abstract: A tuneable radio and method for automatically adjusting the seek sensitivity alignment for seek operations The radio has a radio receiver for receiving broadcast radio wave signals, and a tuner adjustable for selecting from a plurality of radio wave signal channels A detector detects signal strength of the received radio wave signals, and a seek input allows a user to initiate a seek operation to select a signal channel having a signal strength exceeding a seek sensitivity threshold A controller calculates an average signal value and adjusts the seek sensitivity threshold based on the average value The controller adjusts the seek sensitivity when it is determined that the radio has travelled beyond a minimum distance

Nature of Eclipsing Pulsars

Abstract: We present a model for pulsar radio eclipses in some binary systems and test this model for PSR B1957+20 and PSR J2051-0827. We suggest that in these binaries the companion stars are degenerate dwarfs with strong surface magnetic fields. The magnetospheres of these stars are permanently infused by the relativistic particles of the pulsar wind. We argue that the radio waves emitted by the pulsar split into the eigenmodes of the electron-positron plasma as they enter the companion's magnetosphere and are then strongly damped because of cyclotron resonance with the ambient plasma particles. Our model explains in a natural way the anomalous duration and behavior of radio eclipses observed in such systems. In particular, it provides stable, continuous, and frequency-dependent eclipses, in agreement with the observations. We predict a significant variation of linear polarization both at eclipse ingress and at egress. In this paper we also discuss several possible mechanisms of generation of the optical and X-ray emission observed from these binary systems.