FM radio

Frequency modulation is used in telecommunications and signal processing, frequency modulation (FM) conveys information over a carrier wave by varying its instantaneous frequency.

This is in contrast with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant.

Frequency modulation can be regarded as phase modulation where the carrier phase modulation is the time integral of the FM modulating signal. FM is widely used for broadcasting of music and speech, and in two-way radio systems, in magnetic tape recording systems, and certain video transmission systems.

FM signals can be generated using either direct or indirect frequency modulation. Direct FM modulation can be achieved by directly feeding the message into the input of a VCO.

For indirect FM modulation, the message signal is integrated to generate a phase modulated signal. This is used to modulate a crystal controlled oscillator, and the result is passed through a frequency multiplier to give an FM signal. Is also used at intermediate frequencies by all analog VCR systems, including VHS, to record both the luminance (black and white) portions of the video signal. Commonly, the chrome component is recorded as a conventional AM signal, using the higher-frequency FM signal as bias.

FM is the only feasible method of recording the luminance ("black and white") component of video to and retrieving video from Magnetic tape without extreme distortion, as video signals have a very large range of frequency components — from a few hertz to several megahertz, too wide for equalizers to work with due to electronic noise below -60 dB.

Fm demodulator

The NE564 is used as an FM demodulator. The connections for operation at 5 V and 12 V are shown in Figures 21-4A and 21-4B. The input signal is ac coupled with the output signal being extracted at Pin 14. Loop filtering is provided by the capacitors at Pins 4 and 5 with additional filtering being provided by the capacitor at Pin 14. ..

Fm Demodulator Circuit

An LM311 comparator converts a small analog signal to a digital level for the DC4046 phase-locked loop, which is configured as a first-order FM demodulator. This demodulator works with a 50-kHz FM modulated input signal. It has applications in FM light beam receivers or in remote control applications...

Subcarrier Adapter For Fm Tuners Circuit

Op amp Ul and its associated components comprise the 67-kHz bandpass filter. A twin-T network, comprised of four 1100-12 resistors and four 0.0022- capacitors, is connected in the feedback network of the op amp. That gives some gain at 67 kHz and heavy attenuation for frequencies above and below that frequency. An additional passive filter at the input to the twin-T network (containing a 220-pF capacitor and a 10,000- resistor) provides some additional roll-off for.....

FM IF Subsystem with CA3189E

TheCA3189E is a comprehensive FM-IF system designed for high fidelity FM tuners. It includes a three stage FM-IF amplifier/limiter configuration with level detectors for each stage, a double-balanced quadrature FM detector and an audio amplifier that features the optional use of a muting circuit. The advanced circuit design includes desirable special features such as delayed AGC for the RF tuner, an AFC drive circuit, and an output signal to drive a tuning meter and/or.....

Fm Generator

The internal zener on pin 15 of the 4046B supplies a stable voltage to the 3140IC op amp. This amplifier modulates the 4046B V..

Fm Modulator Circuit

The FM modulator is built with a Motorola MC1648P oscillator. Two varactors, Motorola MV-209, are used to frequency modulate the oscillator. The 5000- potentiometer is used to bias the varactors for best linearity. The output frequency of approximately 100 MHz can be adjusted by changing the value of the inductor. The output frequency can vary as much as 10 MHz on each side. The output level of the modulator is -5 dBm. In this prototype, the varactor bias was 7.5 V for.....

Stereo demodulator

This circuit uses a single IC LM1310 to proyide left and right outputs from a composite MPX stereo signal. Oscillator adjust Rl is set for 76 kHz (19 kHz at pin 10). ..

Narrow band FM demodulator

For FM demodulation applications where the bandwidth is less than 10% of the carrier frequency, an XR-J567 can be used to detect the presence of the carrier signal. The output of the XR-567 is used to turn off the FM demodulator when no carrier is present, thus acting as a squelch. In the circuit shown, an XR-215 FM demodulator is used because of its wide dynamic range, high signal/noise ratio and low distortion...

455Khz Fm Demodulator Circuit

Useful for NBFM reception on older shortwave receivers lacking tills capability, This circuit uses a PLL IC, an N565N, to achieve this. It was originally used with an old Hammarlund HQ-170 receiver, ..

565Sca-demodulator

This application involves demodulation of a frequency-modulated subcarrier of the main channel. This popular example uses the PLL to recover the SCA (Subsidiary Carrier Authorization or storecast music) signal from the combined signal of many commercial FM broadcast stations. The SCA signal is a 67l Views: 12 | Votes: 22 | Comments: 0 | Rating: 4 | Rank: 5 | Added: Sep 24, 2012 |

Telemetry demodulator

The circuit recovers an FM audio signal that variesfrom less than 1 kHz..

FM radio with TDA7000

An FM radio on a single chip requiring only a few simple peripheral components. In particular the ship requires only one simple coil and alignment is very easy. The chip includes an RF input stage, mixer, local oscillator, IF amplifier/limiter, phase demodulator, mute detector and mute switch. The output will directly drive a crystal earpiece or could be used with a TBA820M to form a complete portable radio...

@from 42 to 88 Mhz Band

The FM broadcast band was moved immediately after World War II from its original spot just below 50 Mc to the present 88-108 Mc band. Hallicrafters was one company to offer receiving converters for those who had the old FM radio sets. The offerings included a one-tube converter that fits inside a console and draws power from the audio output tube socket (using an adapter)...

@FM Receiver

An FM regenereative receiver using a single FET and one audio amplifier IC...

TDA7000 FM Radio

This extremely simple FM radio receiver circuit is made possible by the special purpose TDA7000 IC. It integrates nearly all the functions necessary to build an FM receiver needing only a few external capacitors and a tuning circuit. Using a simple active RC filter made of only a single inductor, a few resistors and a varicap, this FM receiver will pick up broadcast radio between about 88 and 108 MHz. The mono output signal can then be used to drive a set of high impedance.....

@Digital Data Signal Crosstalk on the Clock

Crosstalk from digital data signals into the clock signal of a data-conversion system can cause hard-to-diagnose problems. This obscure problem is different than the crosstalk from digital data signals into the analog signal path, which was the subject of Part 1. There is value to understanding this different crosstalk problem at a deeper level, so a design engineer can more efficiently understand and troubleshoot a circuit with this type of problem...

@Wideband Display

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 uses the same version 1.1 software as the 5300 and, unless noted otherwise, is known elsewhere on this web site as the 5300 unit.....

@synthesizer generates 19-kHz pilot tone for FM baseband signal

This Design Idea presents a low-cost method of generating the basic 19-kHz pilot tone. The 19-kHz pilot tone comprises a baseband signal, and the L+R and LR signals consist of DSBSC (double-sideband-suppressed-carrier) modulation centered at 38 kHz. For a receiver to correctly demodulate the signal, the transmitted pilot tone and LR signal must synchronize at their respective zero crossings...

@Vital-signs monitor consumes less than 50µA

A remote data-acquisition circuit for monitoring a patient`s vital signs--pulse rate, respiration, and temperature--uses very little power as well as inexpensive sensors and circuits (Figure 1). The data-acquisition portion uses the low-cost CD4000 series of CMOS ICs and consumes less than 50 mA from a 3V battery. The circuit uses 50x oversampled sigma-delta ADCs with a PWM/FM system, which combines three data channels on one RF carrier...

@Stereo Decoder for FM Tuner

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