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FM Radio Circuits
FM Radio Circuits
Powering White LEDs in Series or Parallel Connections
White LEDs are popular for portable equipment LCD backlights because they are less complex, less expensive, and smaller than CCFL backlights. Portable equipment like PDAs, cellphones, and digital cameras require backlights because they are converting to color LCD displays. This article discusses charge-pump and inductor step-up converter...
Circuit Regulates White-LED Bias Current
The compact circuit (Figure 1) overcomes these problems. The regulated buck/boost charge pump in a small µMAX package (U1) has a 100mA output-current capability. Configured as shown, the circuit directly regulates bias current flowing through the white LED. By biasing multiple white LEDs in parallel, it can provide good light distribution. The...
Control Brightness and Power Efficiently of LEDs
This application note describes how LEDs (including white LEDs) work. The note also explains how to drive them in battery-powered LED applications, including lithium-ion (Li+ or Li-ion), nickel-cadmium (NiCd), and nickel metal-hydride (NiMH) rechargeable handheld devices where power consumption is important. LED brightness-matching and the value...
LED stepdown power supply
Below is a proof of concept circuit which needs improvement. The part values shown will run a high efficiency red LED with a Vf of 1.9V from only 2 nicads, right down to 2 volts. For a white LED you will need more batteries and you must increase the 1.0K resistor to a higher value. Current sensing at a mere 18mV over 1ohm makes this stepdown...
FET Controls 2nd LED Array in Switch-Mode LED Backlight
Maxim/Dallas > Designer`s Library > App Notes > DISPLAY DRIVERS Keywords: Single FET Controls 2nd LED Array in Switch-Mode LED Backlight Related Parts APP 1871: Feb 03, 2003 Download, PDF FormatDownload, PDF Format (29kB) APPLICATION NOTE 1871 Single FET Controls 2nd LED Array in Switch-Mode LED Backlight White-LED...
J-Pole Antenna 89Mhz
This antenna is made from 1/2" copper tubing and it is soldered together with plumbing tees, elbows, and nipples..
FM Stereo Broadcast limiter
Only one channel is shown, both channels are identical. The input and output RF filter coils and capacitors should be build on the RCA jacks, keep the leads short and use coax to run the signals to the circuitry. The circuit should be build inside of a metal box for shielding, use metal boxes for all transmitter circuitry.
WA4DSY 56KB RF Modem
This is a prototype of the WA4DSY 56KB RF modem. It is intended for use on amateur packet radio networks. The modem generates RF in the 28 to 30 mhz range and requires and linear transverter to convert the signal to a UHF or microwave ham band. The digital interface is synchronous serial. The modem supplies TX and RX clocks. For more details see...
Circuit Generates Analog Fan-Speed Control
Fan-control circuits range from simple switches that boost the fan speed at a certain temperature, to digitally controlled fans with continuously-variable speed. High-speed/low-speed switches are inexpensive, but the sound of sudden speed changes can be annoying. Digitally controlled fans perform well, but those circuits are more costly, and the...
This is the construction guide for the 5301 wideband fuel mixture display kit. The 5301 is the Tech Edge version (rather than the Jaycar version) of the modified Silicon Chip FMD design, and it features, compared to the original kit, double sided PCBs a new front panel design, in-built RS232 output and superbright GaAlAs 7 segment LEDs The 5301...
NTE789 Stereo Multiplex Decoder
Figure 1 shows the block diagram for the NTE789. The input signal form the detector is amplified by a lowdistortion preamplifier and simultaneously applied to both signal, generated by a local voltagecontrolled oscillator (VCO), is counted down by two frequency dividers to a 38kHz signal and to two 19kHz pilottone supplied by the FM detector...
Stereo Decoder for FM Tuner
No Description available.
Complete PCB design solution combining schematic definition with powerful layout and simulation tools * Integrated design environment combines ease of use with functional depth..
Switching Regulator Boosts Input Voltage
Uses the MAX641 switching controller and an external discrete charge pump to step up the input voltage. This circuit can service low loads and is efficient when the output is two, three, four times the input voltage. Adding the MAX627 MOS driver can further increase the output current capability.
FM Wireless Mic
FM Wireless Mike can transmit voice signals to any FM Radio receiver 100 meters away. The circuit is basically a frequency modulated transmitter working at 100 MHz. The frequency of the transmitter can be varied slightly by changing the trimmer C5. You can use ordinary condenser mike in this circuit. The transistors can be replaced by any low...
10 watt amplifier for 18MHz
This project and your efforts will provide you with a 0.55...3 watt input to easily 10 watt output. The two linear amplifiers are ment for use with QRP SSB/CW/FM/AM transmitters on the amateur bands 15 and 17 meters can be powered from a 12 volt DC supply. The design is a good balance between output power, physical size. The completed amplifier...
Stereo Encoder for FM transmitters
This stereo encoder is a halfway between analogue and digital processing. It 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...
RC 4-Channel FM receiver
This small receiver with reduced range (weight 9g, dimensions 32 x 25 mm) is suitable for slow-flyer, little boats, etc.
This bug can be attached to anything from a glider to a pot plant and you can track it with a radio. Why track a pot plant? The Beeper is the result of many requests for a mini tracking device and introduces a new world of tracking. The circuit is very compact and consumes very little power. It is small enough to be hidden in anything you...
stable guitar FM transmitter
This FM transmitter has a number of features, with a volume control to adjust the input level and a small, neat box to make it easier to attach to a guitar. The volume control is positioned at the end and when turned up fully, the transmitter provides fuzz (distortion).
Field Strength Meter
This Field Strength Meter has been specially designed for our FM bugs. It is capable of detecting very low power transmitters and will assist enormously in peaking many of our FM transmitters that have a coil in the output stage that can be adjusted for optimum output.
LED Power Meter
The LED power Meter is a simple RF detector using diodes to charge a capacitor. The voltage developed across the capacitor is indicated by a multimeter set to a low voltage range. The circuit is soldered together without the need for a PC board, as can be seen in the diagram below and paper clips are used for the positive and negative terminals...
MICRO FM Bug
The circuit consists of three stages, an electret microphone, an audio amplifier and an RF oscillator. The electret microphone consists of only two parts - a FET transistor and a plastic diaphragm. There is nothing else inside the case. The 3-leaded FET has an input, output and earth lead. The mylar diaphragm has been permanently charged with a...
very stable BUG
Is a 100 to 200 metre (100 to 200yds) device having a very stable performance. It can be used as a hand held microphone or left on a shelf to pick up the sounds in a room. It has many interesting features. These will be fully described in the article. One of the most important features of this project is the use of standard components. This...
What got me interested in building these diminutive devices is the S3FM connector assembly made by Switchcraft. The S3FM is simply a 3.5-inch tube fitted with a male XLR at one end and a female at the other, with enough room in the middle to build a mike pad, low-end rolloff network, polarity reverser, or any number of other useful little...
2 Transistor FM Voice Transmitter
Take care with transmitter circuits. It is illegal in most countries to operate radio transmitters without a license. Although only low power this circuit may be tuned to operate over the range 87-108MHz with a range of 20 or 30 metres.
portable FM transmitter
A portable FM transmitter that can be used to replace a FM microphone. This simple transmitter operates from a 9V battery as shown above. I personally built this for a purpose. This is how it happened:- "members of my singing group find it difficult to handle a FM mic in Church. The choir sings in acapella form and the congregation expect us to...
CW Sidetone Generator
This circuit is about as good as it gets for generating morse code tones. It may be used as a code practice oscillator, a tone generator for a keyer, a sidetone oscillator for a CW transmitter or an audio Modulated CW (MCW) generator for an FM transmitter or repeater.
FM stereo multiplex generator
The design philosophy for this circuit was centered on replacing all of the op-amp circuitry found in the earlier circuits with discrete transistors and LC filters. The previous circuits had many (high quality) op-amps in series, this resulted in audible distortion, especially on "ess" sounds. The discrete transistor amplification stages in this...
Low power temperature controller
This circuit was built to stabilize a radio frequency VFO (Variable Frequency Oscillator) for ham radio applications. The circuit has also been used to lower the drift of a Ramsey FM10a micropower FM transmitter.
Micro Power FM Broadcasting
Here are some utility circuits for use with the Ramsey FM10a, and other small FM stereo transmitter kits. This information may be helpful for setting up a micro powered FM radio station. The FM10a and similar kits tend to put out a low quality, broad band output signal. This is not a big problem with a 5-10 milliwatt signal, but amplifying the...
2m VHF FM PMR transceiver to amateur radio converter
The PMR VHF transceiver Motorola Radius M110 (in further text referred as M110) was manufactured by Motorola GmbH therefore being an European radio. Since many professional radio service users has replaced this transceiver with newer gear, a considerable number of M110 has appeared on HAM flea markets. M110 is a simple yet fine transceiver with...
RF Transmitter Circuits
RF Receiver Circuits
RF Amplifier Circuits
AM Radio Circuits
FM Transmitter Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
Digital Signal Integrity
Interconnection and Timing of Digital Circuits
CMOS Circuits Tutorial