AM Transmitter Research Articles

Upaya Radio Elbayu Mempertahankan Pendengar

Radio El Bayu is one of the AM radios that still exist today. This radio is also the only active radio station in Gresik. This radio, established in 1994, has a target audience of 40 years and over. In its time, this radio often held an event for the local community to build its image among the public. When many radios broadcast with FM, El Bayu remains consistent with the AM transmitter used. In fact, in Indonesia itself, it is very rare to find radio stations that still use this AM transmitter. Although the number of radio listeners has decreased, some people still choose to listen to radio channels. In this journal, we will discuss the efforts made by El Bayu Radio to retain radio listeners, considering that El Bayu still uses AM transmitters and has to compete with current digital media.

DRM DIGITAL BROADCASTING SYSTEM AUDIO PATH QUALITATIVE CHARACTERISTICS

The Digital Radio Mondiale (DRM) digital broadcasting system is the only ITU-approved digital broadcasting system for the LF, MF and HF bands. Numerous theoretical and field studies, as well as operating experience over the past 20 years, have allowed a good study of digital broadcasting networks organization according to this standard. However, some of the issues related to the audio path formal characteristics were not considered. The article discusses the audio coders used in the DRM system and the available data rates in various immunity modes. A set of test signals for instrumental measurements and listening has been developed. The results of experimental measurements for various data rates are presented. It is shown that the range of modulating frequencies in 7 modes of immunity is not narrower than for FM transmitters. In another 5 modes of noise immunity, the range of modulating frequencies is narrower than for FM transmitters, but wider than for AM transmitters. It is confirmed that at data rates of more than 16.5 kbps, the DRM transmitter signal quality becomes no worse than AM signal transmitter quality. Above 24 kbps, the DRM transmitter signal quality becomes comparable to that of an FM transmitter.

Design of 1 MHz Solid State High Frequency Power Supply

High Frequency Power supply (HFPS) is used for various applications like AM Transmitters, metallurgical applications, Wireless Power Transfer, RF Ion Sources etc. The Ion Source for a Neutral beam Injector at ITER-India uses inductively coupled power source at High Frequency (∼1 MHz). Switching converter based topology used to generate 1 MHz sinusoidal output is expected to have advantages on efficiency and reliability as compared to traditional RF Tetrode tubes based oscillators. In terms of Power Electronics, thermal and power coupling issues are major challenges at such a high frequency. A conceptual design for a 200 kW, 1 MHz power supply and a prototype design for a 600 W source been done. The prototype design is attempted with Class-E amplifier topology where a MOSFET is switched resonantly. The prototype uses two low power modules and a ferrite combiner to add the voltage and power at the output. Subsequently solution with Class-D H-Bridge configuration have been evaluated through simulation where module design is stable as switching device do not participate in resonance, further switching device voltage rating is substantially reduced. The rating of the modules is essentially driven by the maximum power handling capacity of the MOSFETs and ferrites in the combiner circuit. The output passive network including resonance tuned network and impedance matching network caters for soft switching and matches the load impedance to 50ohm respectively. This paper describes the conceptual design of a 200 kW high frequency power supply and experimental results of the prototype 600 W, 1 MHz source.

2.NHKの中波ラジオ送信機

2.NHKの中波ラジオ送信機

Design and Construction of a Simple but Efficient and Cost Effective Amplitude Modulated Transmitter Using Locally Available Materials

This work is an exploration of the design foundation and construction of an AM Transmitter. An AM transmitter controls the transmitting and broadcasting of signals that supports information conveyance in the AM Bandwidth. A brief introduction of the concept of AM transmission is followed by detailed discussion of design and construction. The discussion is organized under the 5 stages of the AM transmitter unit, namely; Power supply, Audio Amplification, carrier wave oscillation, modulation, and the RF Power Amplification Stages.

Alternative Methods to Obtain Ground Conductivity

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The radio planning of systems in lower frequency bands, such as LF and MF, makes use of ground conductivity at these frequencies, as it determines the attenuation of the surface wave, characteristic of the propagation in these bands. In this paper, three alternative methods to obtain an estimation of the conductivity are presented and compared. The first one is based on measurements of the electric field strength generated by AM transmitters. Although it is considered the most accurate, it is also the most expensive as it requires extensive and detailed measurements that are not always feasible. The second method relies on several terrain characteristics that are known to be related to the conductivity, and uses reference conductivity values from similar areas. The third method makes use of remote sensing data, information that is readily available worldwide at low cost. The methods are compared through their application in a research work carried out in Mexico. The results show that these approximate methods can yield results with reasonable accuracy, when compared with the results obtained from field strength measurements. </para>

Biotelemetric Monitoring of Brain Neurochemistry in Conscious Rats Using Microsensors and Biosensors

In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O2 and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems.

A Precision, Low-Cost GPS-Based Transmitter Synchronization Scheme for Improved AM Reception

This paper describes a highly accurate carrier-frequency synchronization scheme for actively, automatically locking multiple, remotely located AM broadcast transmitters to a common frequency/timing reference source such as GPS. The extremely tight frequency lock (to ~1 part in 109 or better) permits the effective elimination of audible and even sub-audible beats between the local (desired) station's carrier signal and the distant stations' carriers, usually received via skywave propagation during the evening and nighttime hours. These carrier-beat components cause annoying modulations of the desired station's audio at the receiver and concurrent distortion of the audio modulation from the distant station(s) and often cause listeners to ldquotune outrdquo due to the low reception quality. Significant reduction or elimination of the beats and related effects will greatly enlarge the effective (interference-limited) listening area of the desired station (from 4 to 10 times as indicated in our tests) and simultaneously reduce the corresponding interference of the local transmitter to the distant stations as well. In addition, AM stereo (CQUAM) reception will be particularly improved by minimizing the phase shifts induced by co-channel interfering signals; hybrid digital (HD) signals will also benefit via reduction in beats from analog signals. The automatic frequency-control hardware described is inexpensive ($1000-$2000), requires no periodic recalibration, has essentially zero long-term drift, and could employ alternate wide-area frequency references of suitable accuracy, including broadcasts from WWVB, LORAN-C, and equivalent sources. The basic configuration of the GPS-disciplined oscillator which solves this problem is extremely simple. The main oscillator is a conventional high-stability quartz-crystal type. To counter long- term drifts, the oscillator is slightly adjusted to track a high-precision source of standard frequency obtained from a specialized GPS receiver (or other source), usually at 10.000 MHz. This very stable local reference frequency is then used as a clock for a standard digitally implemented frequency synthesizer, which is programmed to generate the specific carrier frequency desired. The stability of the disciplining source, typically ~1 part in 109 to 1011, is thus transferred to the final AM transmitter carrier output frequency.

A study on high‐efficiency short‐wave AM transmitter

AbstractIn a short‐wave (3 to 30 MHz) high‐power transmitter, the modulation section is fabricated with semiconductors, but the total semiconductor realization including the final‐stage PA is difficult and has not been accomplished to date. The authors' objective is to achieve total use of semiconductors for realization of a 100‐kW‐class short‐wave high‐power transmitter. An optimal power device (MOSFET) to obtain high efficiency is selected. In addition, a circuit for realization of high efficiency and a synthesis method for excellent linearity are proposed. In the short‐wave band, there is a problem of increased loss due to parasitic diodes for the digital‐processing AM modulation device used in the middle‐frequency range. It is shown that the method cannot be applied directly. Further, an optimum modulation format and a circuit configuration for realization of a short‐wave high‐efficiency AM transmitter are proposed. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(3): 33–41, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20283

Countermeasures of Stimulated-Raman-Scattering-Induced Video Distortion in 1.65 µm Optical Time-domain Reflectometer On-line Monitoring 1.55 µm Cable Television System

The countermeasures of stimulated-Raman-scattering (SRS)-induced baseband video distortion in the 1.65 µm optical time-domain reflectometer (OTDR) on-line monitoring 1.55 µm amplitude modulation with vestigial sideband (AM-VSB) cable television (CATV) transmission system are investigated theoretically and experimentally. The countermeasures entail the reduction in the optical modulation index (OMI) of the AM transmitter, OTDR peak power and/or pulse width. The results of numerical simulations and experimental measurements are in good agreement. Moreover, the countermeasure for eliminating the SRS-induced baseband video distortion by the 1.31 µm OTDR on-line monitoring technique is investigated and demonstrated.

&quot;Parts Selection for Reliability and safety Improvement&quot; Reliability Improvement of AM Transmitter (Part 1)

&quot;Parts Selection for Reliability and safety Improvement&quot; Reliability Improvement of AM Transmitter (Part 1)

MF AM grounded dipole for stereo and digital transmissions

Modern MF AM transmitter output impedance has been chosen to be 50 ohms unbalanced. For this reason high power 50 ohms coaxial lines have been designed and manufactured, rigid or almost flexible in order to connect the transmitter in the station building and the far away radiating system at one or more wavelengths. At MF frequencies the radiating system is generally a standard classical monopole where a matching system close to the monopole is needed to obtain maximum radiation efficiency. The proposal here is to use a radiating system made up of a grounded tower close to half a wavelength tall with a cylindrical skirt around the tower's lower part. The skirt is fed directly from the 50 ohm coaxial line at a point whose impedance is very close to 50 ohms, avoiding the matching system and improving the radiation efficiency within a good bandwidth suitable for stereo or digital transmissions. Design permits a low standing wave ratio within the information passband necessary to obtain the lowest information distortion. Scale models have been designed, constructed and measured obtaining similar results as predicted by calculations in the MF frequencies. The advantages of a grounded tower are discussed.

Single-longitudinal-mode fiber laser with a passive multiple-ring cavity and its application for video transmission

A single-longitudinal-mode erbium-doped fiber laser with a passive multiple-ring cavity (MRC) is proposed for the first time to the authors' knowledge. The laser is fundamentally structured by insertion of three different short ring cavities, which serve as mode filters, into the main cavity. When it is combined with a mode-restricting intracavity fiber Bragg grating, the MRC resonator ensures single-longitundinal-mode laser oscillation. The laser can successfully suppress side-mode frequencies of as much as 1 GHz and provide an output power of 23 mW with a side-mode suppression ratio of 51 dB at 1533 nm. The short-term linewidth of the laser output measured is ~2 kHz . The ability of this fiber laser to act as an AM transmitter source is also demonstrated.

ディジタル位相シフトを利用した新型ＡＭ送信機

This paper presents a new type of AM transmitter which can produce AM waves directly from digitized audio signals by shifting the phase of the signals digitally using a frequency twelve times as high as the carrier. The transmitter consists of six switching-type RF power amplifiers with a maximum peak output power of 330 W, a 12-bit A/D converter, a ROM for waveform compensation (arc sin etc.), phase shifters/selectors for producing carrier pulse width signals, and a power combiner. The transmitter displays high overall efficiency of 67% (RF output/DC input), an SN ratio of 68 dB, and about 0.9% total harmonic distortion at 80% modulation.

Cortical spreading depression blocks prostaglandin E1 and endotoxin fever in rats

We have tested the hypothesis that the cortex may play a role in the development of fever. Male Sprague-Dawley rats equipped with AM transmitters for telemetric measurement of body temperature were given intracerebroventricular prostaglandin E1 (PGE1), corticotropin-releasing hormone (CRH), or intravenous E. coli endotoxin. Application of cotton pellets soaked with 3.3 M KCl to the frontal cortex (to induce spreading depression) significantly reduced fevers to PGE1 and endotoxin when compared with fever magnitude with 0.9% NaCl application to the cortex. Neither CRH-induced hyperthermia nor normal body temperatures were altered by the spreading depression. Our results reveal a novel action of spreading depression on thermoregulatory function and indicate cortical involvement in the development of fever.

Performance measurement and test techniques for modern AM broadcast transmitters

The numerous tests required in evaluating the performance of a modern AM transmitter are discussed. Both laboratory tests of novel products and environmental tests are covered. The latest attainable performance measurements, environmental testing requirements, and field condition simulation tests are examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A signal subspace method for adaptive interference cancellation

An interference cancellation technique that combines a signal subspace approach with adaptive adjustment of the weight vector is derived. The weight vector is constrained to lie in a signal subspace computed by eigendecomposition of the covariance matrix of the array outputs. The weight vector is rotated to maximize the output signal-to-interference ratio. The technique does not require array calibration as in other subspace methods. This technique applies to receiver arrays for digital communication signals. The case of a BPSK signal modulating an AM transmitter is analyzed in some detail. Numerical examples illustrate the behavior of the algorithm. >

AM stereo — fact or fiction?

Over 3000 AM transmitters attempt to operate in the 120 medium-frequency waveband channels in the European broadcast area. This article discusses whether the numerous proposals for AM stereo broadcasting have any merit against this background

A minimum component AM transmitter to monitor electronic brain stimulation

Construction of a light weight AM transmitter which can be used to monitor implanted electronic brain stimulators is described. The unit can operate continuously for 40 hours on a single battery and can easily be carried by a small laboratory animal. The range of the unit is limited to approximately 1 meter and the transmitted signal can be detected by a standard AM broadcast band receiver. The unit is simple to construct, inexpensive, and reliable in performance.

Measurement of the Frequency Correlation Function of Fading Channels Using AM Stations as Signal Sources

Measurements of the statistical characteristics of a proposed HF channel are usually required before such a channel is designed. These measurements require an elaborate test setup with test transmitters at the proposed transmitting sites. This work is therefore both time consuming and expensive, particularly when alternative locations are considered. This paper describes a method which allows the signals radiated from an AM transmitter to be used for determination of the frequency correlation function for the channel. The method is based on the fact that the frequency functions of the upper sideband (USB) and lower sideband (LSB) of an AM signal are complex conjugates. The received signal is filtered into its USB, carrier, and LSB components. The USB and LSB signals are synchronously demodulated. Since the two signals are transmitted on different frequencies, they can be used for frequency correlation determinations. The modulating signal can, in most cases, be considered as random noise. Its effects are removed by normalization.