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Directional RF Power Meter
2009-01-04 16:59:00
Here's a powerful bench-top power meter that is based around two AD8307 log detectors which have a 90dB dynamic range for signal strength measurements. Tie that to a good directional coupler and you have yourself a very easy to build and calibrate power meter! Since the AD8307s respond very quickly to changes in signal level they are also perfect for deriving percent of modulation, peak power, average power and more. The real advantage to this power meter is its ability to measure very small signals from low-power transmitters. Because it also has a directional coupler, you can also check the match of your antenna by looking at the VSWR reading as well as reflected power. The less reflected power, the more power being transmitted over the air. Without this power meter, you might simply have to go with your best guess. Since this unit also contains a directional coupler you can not only measure forward power (power which exits the generating device), but you can also measure rev...
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FM RF Amplifier 88-108 MHz 100mW-8W
2008-12-29 01:10:00
Here's FM RF amplifier 100mW-8W for 88-108 MHz. This amplifier circuit using the transistor BFR96 and 2SC1971 and equipped with a low pass filter Click link for more: Schematic Photo View Parts List Silkscreen Copper bottom Component layout
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Where Go for Test Equipment Rental
2008-11-22 02:24:00
Here is the best place to rent equipment when you do not want to buy it. At Test Equity, they not only strive to provide the best in new and used test equipment, but also the widest variety of purchasing options available. Whether your needs include buying, renting, or leasing equipment, TestEquity has a plan that will meet those needs. Below is a brief summary of our Test Equipment Rental and Leasing options. TestEquity is an Authorized Agilent Rental Company. TestEquity offers fast delivery from stock, expert technical assistance in helping you select the right instrument, and flexible rental plans. Download Credit Application...

Small AM Transmitter
2008-11-20 19:14:00
Here's a small AM Transmitter you may needed. It/s built into a plastic project box, and uses a piece of perfboard rather than a printed circuit board. Of course, a PCB would have been much more elegant, but designing and making one would have increased construction time by at least five times! The RF transformer of the transmitter is actually a 455kHz IF transformer taken from a junked transistor radio from the 1970s. I removed its internal 470pF capacitor. With the external 100pF capacitor it can be easily tuned to 1MHz. It must have roughly 250 microhenry in the higher impedance winding, and the turns ratio of the low impedance one is about 1:10. The antenna of this AM Transmitter is a resonant multiturn loop. It has 19 turns of common household stranded wire, wound on a piece of strong cardboard that has 11 slits cut into its periphery. Why 11? Well, 10 or 12 sounds nicer, but we need an odd number, so that we can make the low parasitic capacitance winding! The wire change...
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4 Channel Video Mixer Edirol LVS-400
2008-11-16 13:06:00
Here's a video mixer LVS-400 from Edirol , It  compact, simply-operated 4 channel video switcher is so easy to use, that even without any previous video experience, you can create very professional video transition and key effects for a professional video performance. LVS-400 is ideally suited for installations and It  offers both BNC and S-Video inputs and outputs. It includes 17 back-lit buttons for easy control in low-light environments, a T-Bar for manual transitions, a time control for button-controlled transitions and two effect control knobs. You can easily cut from source to source, simply by pressing the button of the output you want. Main Features of LVS-400 Video Mixer : Easy to operate User Interface for mixing Video Sources. Back-lit Buttons for easy operation in low-light. BNC connectors for firmly locking cable connections. High-quality and stable video image. Digital processing for impressive image quality and two individual frame synchronizers. Picture I...
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Circular Dipole Broadcast Antenna 88-108 MHz
2008-11-15 21:34:00
Here's a Circular Dipole Antenna construction for FM broadcast 88-108 MHz. This antenna is made of copper pipes with a diameter of 15 mm. This is a dual antenna type circular polarization Vertical / Horizontal, one of its features is the main penetration, that is to cover urban areas. This Circular Dipole Antenna designed by EA3ABN. See the diagram below for antenna dimension and download documentation for its construction DETAILS OF CONSTRUCTION   You can design a circular dipole antenna to your own needs, based on the design of antenna above. Welcome to experiment. Circular Dipole Broadcast Antenna 88-108 MHz in detail

Directional Coupler with RF Filter for 88-108 MHz
2008-10-28 23:52:00
Here's Directional Coupler equipped RF filter with bandwidth is wide enough to pass any VHF 87.5 to 108 Mhz, cutoff frequency of 115 MHz being something similar. The harmonic 2 is located at 65 dB and harmonic 3 at 70 dB, to ensure optimum purity of the carrier. The low-pass filter is made in cells L / C type Butterworth, mounting parallel to 9 poles. Impedance input and output is 50 ohms. The low-pass filter is followed by the party meter reflectometer composed of a main line and two adjacent lines. Each of these lines are loaded by 50 ohm resistors R2 and R3-47ohms. These lines are direct and thoughtful fitted on each of them an attenuator, but in practice, I realized that these were not necessary attenuators, you need to remove R1, R6, R4 and R9 - 100Ohm strap and R5 and R8-82ohms.    HF detection is provided by two circuits at-Linear Technology, LTC5505 this circuit is expected of origin for higher frequency but retains excellent at 100Mhz, or for that choice. Re...
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20 dB/150 Watt RF Attenuator
2008-10-17 22:44:00
Here is an attenuator schematic for your spectrum analyzer. It's simple, easy and cheap way to make fairly high power RF attenuators. These are useful for directly connecting the output of a high power RF amplifier into a spectrum analyzer, frequency counter or other piece of test equipment (additional attenuation maybe required). This attenuator circuit  is based around a Bird Component Products attenuator chip, which are available from Radio Dan for $30 a piece. When properly heatsinked, they will dissipate a continous 150 Watts of power. Here's 150 watt rf attenuator picture:

Stereo Tool 3.30 for Winamp Plugin
2008-10-09 18:30:00
This Stereo Tool application software is a Winamp plugin that delivers professional quality audio processing - for free. Stereo Tool is available in a free and a registered version. The registered version is intended for commercial users of Stereo Tool, especially aimed at FM radio stations. The big commercial radio stations use expensive equipment that ensures that all songs sound the same, and that they sound good on a wide range of cheap up to expensive audio systems. Now Stereo Tool offers you similar processing, which you can use while listening to your own music. What does Stereo Tool 3.30 offer for sound processing, please: Download Stereo Tool 3.30 More about Stereo Tool 3..30
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5W Chinese PLL FM Transmitter With LCD
2008-09-24 07:57:00
Here's PLL FM transmitter circuit from china. This circuit uses the familiar 2SC1971 for final power amplifier stage. Click image below  for enlarge  the circuit schematic. The PLL controller of the FM transmitter use SAA1057 and PIC16F628 (download HEX file). If want to change the active component, here's the list: 2SC2458 = BC547 2SA1048 = BC557 2SK192 = J310 2SB562 = BD136, BD138, BD140 2SC1923 = BF199 of BRF91 2SC1923 = BF199 or BRF91 2SC2053 = BRF96 2SB1135 = BD136, BD138, BD140 MV2105-09 = BB105, BB119      Printed Circuit Board (PCB) for this FM transmitter circuit is 155 mm x 120 mm. All coils are 0.8 mm copper wire with a 6 mm diameter. Please see parts used from schematic.
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RF Spectrum Analyzer Design
2008-09-21 09:59:00
This electronic projets is an RF Spectrum Analyzer design. The sources of projects divided by into two parts and it taken from QST Magazine. Even if you don't build the project there's some great information in here regarding RF filters, mixers, oscillators and more. In part one, described the design and construction of a simple, yet useful spectrum analyzer. This installment presents some applications and methods that extend the underlying concepts. Amplifier Gain Evaluation Amplifier Intermodulation Distortion Return-Loss Measurements Antenna Measurements Transmitter Evaluation Spectrum Analysis at Higher Frequencies Download : Spectrum Analyzer Part One - Spectrum Analyzer Part Two
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Wilkinson Splitter-Combiner Designer
2008-09-13 17:11:00
Here's the formula for designing Wilkinson Splitter -Combiner your RF power. You can choose frequency you want and it's not recommended for above 400 MHz. Use it for design your FM Power Splitter-Combiner 88-108 MHz. For design the splitter-combiner you need to measure Capacitances (C1, C2, C3) and coil inductance (L) and layout PCB you can draw it like this one. Link for online software (CGI) for determine C and L : Wilkinson Splitter Combiner Download software for calculate coil inductance (L)
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TV Transmitter for VHF Low Channel
2008-09-05 23:05:00
This transmitter circuit transmits your VCR or camera signal to any nearby TV set with great audio and video quality. Please be aware that this kit is a real transmitter and can be received by others - whether they want to or not! The TV transmitter can be tuned for channel 3-6 (frequency 61.25-83.25 MHz). The signal of the tansmitter is very stable. Remember since we are transmitting locally, your TV set should have a nearby antenna connected such as a pair of rabbit ears or a short dipole style antenna. You cannot operate the TV with the outdoor antenna or the local cable TV system hooked up to it - after all, their master antenna may be located 30 miles away!     Finished TV transmitter can be installed in a variety of enclosures of your own design and choosing. Link Source: www.ramseykits.com
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500W Multi-use VHF Power Amplifier Up to 500 MHz
2008-08-30 03:10:00
This circuit is 500 watt Multi -use VHF Power Amplifier for frequency up to 500 MHz. This amplifier module incorporates microstrip technology and a single BLF369 mosfet transistor. Input/Output 50 ohms and Power out 500W minimum with a 3 to 5 watt input. Power Supply requirements 22.5 Amperes 32 volts. Schematic Circuit Here's the simple schematic circuit VHF power amplifier. Click image for enlarge schematic. Printed Circuit Board and Layout Below power amplifier PCB and component layout. For more info about power amplifer transistor click download link below: Download BLF369 Datasheet for Parts List

80 Watt FM Stereo Transmitter
2008-08-07 09:23:00
This transmitter circuit was designed from the ground up to provide very high sound quality, coupled with excellent frequency stability, reliability, etc. It can be used as a standalone transmitter to serve a medium-sized town, or as an exciter to drive a kilowatt-class power amplifier to serve a large city. It is designed to work from 13.8V nominal voltage, so that it can be run from a common communications power supply in parallel with a backup battery. In the event of a power cut, the transmitter can keep operating from the battery, at slightly reduced power as the voltage drops. It consists of four modules, the three most important of which are ready, tested, and described below. The fourth module has not yet been built, and might never be built, but I will describe its basic functions so that you can design it, if you want. The audio processor and stereo encoder The textbook way of processing and encoding a stereo signal for FM transmission goes like this: 1) Take both chann...
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PIC FM Stereo Encoder
2008-07-22 14:33:00
This application circuit is a digital analogue processed stereo encoder that combines the best from both domains to provide high-quality and easy to build device. The sampling frequency used in this stereo encoder is 97 times higher than the pilot tone frequency. This makes very easy to reject all spectral residues around the sampling frequency without affecting the main signal characteristics. Using of a microcontroller allows to build this stereo encoder with reduced part count and get excellent results in real operation.  Characteristics: Signal overshooting prevention Low noise and distortion No adjust (only pilot tone level and output level) High channel separation and spectral purity in common operation RDS input and pilot sync. output makes easy to connect any RDS encoder Microcomputer controlled, hex file provided for free All parts are easy to buy (incl. crystal) Supply voltage: 9-16 V (stabilized) Quiescent supply current (12 V): 34 mA Audio 19 kHz rejection: 40 dB ...
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AM Stereo Decoder with MC13208AP
2008-07-18 15:06:00
The MC13028A is a third generation C?QUAM stereo decoder targeted for use in low voltage, low cost AM/FM E.T.R. radio applications. Advanced features include a signal quality detector that analyzes signal strength, signal to noise ratio, and stereo pilot tone before switching to the stereo mode. A ?blend function? much like FM stereo has been added to improve the transition from mono to stereo. The audio output level is adjustable to allow easy interface with a variety of AM/FM tuner chips. The external components have been minimized to keep the total system cost low. Features: Adjustable Audio Output Level Stereo Blend Function Stereo Threshold Adjustment Operation from 2.2 V to 12 V Supply Precision Pilot Tone Detector Forced Mono Function Single Pinout VCO IF Amplifier with IF AGC Circuit VCO Shutdown Mode at Weak Signal Condition   Functional Diagram  The MC13028A is designed as a low voltage, low cost decoder for the C?QUAM AM Stereo technology and is completely comp...

What is AM Stereo?
2008-07-15 18:31:00
AM Stereo is the technology that allows AM radio stations to broadcast with high-fidelity Stereophonic sound, far exceeding the quality normally associated with regular monaural AM radio. AM Stereo provides clear full-dimensional Stereo sound that envelops the listener with fidelity usually thought of as something only found on the FM band. AM Stereo has been used all around the world for over two decades and is employed by hundreds of stations on every continent. Since its introduction, millions of AM Stereo receivers have been sold for home, car, and portable listening enjoyment. AM Stereo is a robust analog system that has been optimized for high performance reception and audio quality even with weak, distant signals. The greater long-distance range of AM signals, especially at night, regularly brings forth stations from hundreds or even thousands of miles away featuring true Stereo sound, something the FM band is incapable of. And yet, AM Stereo is fully compatible with all reg...

1KW Mosfet FM Amplifier Service and Operating Manual
2008-07-01 18:08:00
High gain MOSFET transistors and systematic use of state-of-the-art manufacturing methods, have helped us to find effective solutions for the design of this new equipment. The amplifier, of simple and rugged construction, is able to satisfy the requests of all those end-users looking for top-quality equipment at reasonable prices. The RF power input is divided by 4 by means of a power splitter and is then connected to 4 x BLF278 MOSFETs.The power amplifier is lightweight with broad-band characteristics over the entire VHF FM range. The compact design and the internal configuration of the modules, allow excellent access to all components. All the power components are generously over-rated to ensure excellent reliability. The cooling system of the equipment makes possible to keep all components which dissipate heat, at low temperature figures, thus permitting reliability and very high MTBF.1 KW Power Amplifier Module The input power of the module is connected to a Wilkinson splitter, ...
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40 MHz Garage Door Opener Transmitter
2008-07-01 10:40:00
This electronic circuit is the newer and revised version of the garage door opener transmitter. The transmitter is a PIC based on 40 MHz Microchip?s 16F630 microcontroller. A 10 switch DIP-switch is used for setting the code. To save space, we used a different HF output coil.More about circuit Schematic , PCB files and hex code please download here
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Digigram Announced New VX and PCX Multichannel Sound Cards
2008-06-27 07:59:00
Digigram is taking advantage of the Broadcast Asia tradeshow in Singapore to announce the availability of a fully updated multichannel sound card range.Among the latest iterations of the VX series to be introduced in Singapore this week, the VX822HR (PCI interface) and VX822e (PCI express interface) are multichannel sound cards designed for demanding broadcast applications such as live-assist, permanent and multichannel playback.For applications such as automated recording and play-out, multichannel production and all applications requiring two stereo I/Os, Digigram is also introducing the VX442e multichannel sound card.Software vendors will also be able to take advantage of the new PCX440HR and PCX440e sound cards offering 4/4 analog I/Os, thus being perfect candidates for such missions as auto-recording or archiving.Digigram is offering a convenient online tool allowing for a rapid selection of the right card for the right application, based on I/Os, drivers and other relevant cri...
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Dalet 5.1 The World Standard for Radio Production and Playout
2008-06-27 07:46:00
Dalet 5.1 provides a comprehensive, end-to-end solution for radio stations seeking a digital production and playout system. Scalable, Dalet 5.1 grows with the needs of your operation. All music, audio files, associated metadata and programming information are stored in a central content catalogue which can be accessed from any workstation connected to a standard Ethernet computer network: a radio station can easily start with a couple of workstations and expand its operations as it goes.The Dalet 5.1 interface is Windows based so it is user friendly. The infrastructure it runs on uses mission-critical computer technology so as to guarantee on-air reliability; Dalet 5.1 takes advantage of the latest network, server and storage technology so broadcasters can choose the platform they need to ensure the level of availability they require. Finally, with over 35 distinct modules, Dalet 5.1 is incredibly flexible. It covers the whole workflow from distributed ingest and multitrack editing ...
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50-800 MHz Video Modulator With TDA6800(T)
2008-06-22 17:26:00
The TDA6800 is a modulator circuit for modulation of video signals on a VHF/UHF carrier. The circuit requires a 5 V power supply and few external components for the negative modulation mode. For positive modulation an external clamp circuit is required. This circuit can be used as a general purpose modulator without additional external components.Features· Balanced modulator· Symmetrical oscillator· Video clamp circuit for negative modulation· Frequency range 50 to 800 MHz (datasheet)

100mW TV Transmitter
2008-06-20 20:37:00
The TV transmitter circuit is simple and really quite crude, but it does include MONO sound. These are one 12v DC 1A series regulator chip, and one 8v DC 1A series regulator. I fed the 8v regulator from the output of the 12v regulator. The rest of the circuit looks like this.The RF GeneratorIt is a free-running Variable Frequency Oscillator (VFO) using just one coil and one capacitor to determine the frequency. Change this as you will. The basic circuit uses a 150pf from the Base of the RF transistor to ground, so that TR2 operates as a "common-base mode" (grounded base) amplifier. The tuned circuit in the collector and the capacitor from collector to emitter provide tuning and feedback.A low-impedance tapping of the coil drives TR3, which is a class-C amplifier. Unlike the V5 FM transmitter, this stage does provide RF amplification; about 14dB. It also buffers the antenna circuit from the oscillator, and is the stage that is modulated by means of the supply voltage.The collector lo...
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A Wifi (V)SWR Meter
2008-06-17 08:29:00
The circuit on this page serves as a Voltage Standing Wave Ratio meter or VSWR meter for the VHF-UHF-SHF frequency range. This includes the Wifi (802.11b/g), 2m, 70cm and 13cm Radio Amateur bands.The device consists of two parts. One RF head and a (preferably analog) indicator.The picture to the rights shows the Wifi SWR meter Mk-III - the third generation of the design.An external SWR sensor is attached to the indicator with a BNC-BNC cable.An Analog indicator is used to read the VSWR. This meter has a Peak-Hold circuit with a 9 Volt alkaline battery power supply. There is only one control to control the power ON/OFF and meter Sensitivity. Meter sensitivity can be adjusted to accommodate several RF sources, such as a Wifi Access Point, or VFO.RF Input power must be somewhere between 15 and 20dBm (30 to 100mW)Source: http://pe2er.nl/wifiswr

A Video Amplifier For Satellite Receivers
2008-06-03 07:37:00
Almost all receivers have a built-in level controls which are adjusted by their manufacturer to give the correct output level for a standard satellite input signal. In some cases this control can be advanced far enough to lift ATV signals to the same output level but most receivers will need this design adding to assist them. There is a penalty to pay for winding an amplifiers gain up, given that the gain x bandwidth is a constant, the bandwidth is proportionately narrowed which results in poorer picture quality. Adding extra gain, such as this device does, will always be a better solution.By using a split and isolated supply, the input and output capacitors normally used in this kind of amplifier are eliminated. Bandwidth goes from DC up to more than 10MHz.The PCB is small enough to fit upright inside most satellite receivers. Connect "A" to the old video output point and use "C" or "D" as the new output point. The two outputs can be loaded simultaneously. VR1 sets the...
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Crystal-Based FSK Transmitter RF9901
2008-05-24 20:50:00
The RF9901 is an FSK transmitter that can be used to transmit FSK data using an RF carrier frequency in the range of 400MHz to 930MHz. This device is intended for and ideally suited to both European and United States ISM band applications. The RF9901 evaluation board (RFMD Part Number RF9901PCBA) utilizes a Colpitts oscillator to generate the reference frequency for the PLL phase detector. The PLL consists of an integrated voltage controlled oscillator (VCO), a divide by 32 prescalar, and a reference frequency oscillator amplifier. The output carrier frequency is then the reference frequency multiplied by 64.Which Topology?The Colpitts oscillator is only one of many types of oscillators that could have been used and was chosen primarily for its low parts count. Other oscillators have various tradeoffs for the designer which may result in choosing another oscillator type.This article does not delve into oscillator design, but is simply to provide assistance in understanding why the ...
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Stereo Encoder on A Chip NJM2035
2008-05-22 20:24:00
The stereo encoder consists of three main stages. Pre-emphasis, digital encoder and mixer stages. Pre-emphasis stage is achieved by using two 47K resistors and two 1nF capacitors. This helps to eliminate the noise that is produced during the FM transmission of your audio signal.Second stage that is built around NJM2035 is a digital encoder. All of its internal blocks except for two audio amplifiers (pins 1 & 14) that act as separators are created using digital circuits. The first digital circuit is a 38KHz oscillator that is generated by using external 38KHz crystal (pin 7), 10pF capacitor (pin 6) and 100pF bypass capacitor (pin 5). Once 38KHz frequency is generated it is then buffered and divided into two 19KHz signals with a phase difference of 180 degrees. Once that is done these two frequencies are connected with two time division MPX digital alternating switchers ,one for each audio channel. Here audio channels are switched between each other with a total frequency of 38KHz...
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2.4 Ghz Field Strength Meter
2008-05-16 23:01:00
What can you use to test how effective your antennas are for 2.4 Ghz? Which antenna has the best gain or, how do you know that there is any 2.4Ghz RF transmitted? Here are the details on how to build a general purpose 2.4Ghz Radio Frequency Field Strength Meter .This one was built using the microwave rated diode from a MICROTEK solid state microwave leakage detector (purchased from Dick Smith Electronics for around $24) these diodes can be more expensive than that if purchased in single units from electronics suppliers. There may be other suitable diodes available. Electronics stores also sell Schottky Hot Carrier Diodes that will probably also be suitable for this application. I'll be attempting to build other units that use these instead.The antenna is a 2 element quad. I've orientated it in the diamond configuration so it should be effective for both horizontal and vertically polarised signals. You could build the antenna in the vertical or horizontal sense if you like. The ante...

A Small FM Transmitter With Loop Antenna
2008-05-16 22:05:00
This small Low Power FM transmitter with Onboard Magnetic Loop Antenna that designed by Radio Morningstar. It's suitable for home fm broadcasting. As seen on YouTube Page.This is the PCB board layout for a small LPFM transmitter that i'l showed on Youtube. This new design is even more powerfull, using 4 instead of 2 transistors. The range will go up to 2 kilometers or even 4 - 7 km using een external twinlead fed 300 ohm folded dipol antenne. Or use just 2 transistors for less range using a 100 Ohm Emitor resister instead of the 33 Ohm for lower battery consumption.Take good notice by placing the transistors , for the BF 199 the connections are 1 Basis 2 Emittor 3 Collector. One set transistors is placed 180 degrees backward , be sure all the collectors are connected at the antenna loop. LinkPCB Layout with components :The PCB Layout , print this 10 x 15 cm on your printer to get the right printfolie for exposing your PCM material:The component's silkscreen:
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