Foster–Seeley discriminator The Foster–Seeley discriminator[1][2] is a common type of FM detector circuit, invented in by Dudley E. Foster[3] and Stuart. FOSTER-SEELEY DISCRIMINATOR The FOSTER-SEELEY DISCRIMINATOR is also known as the PHASE-SHIFT DISCRIMINATOR. It uses a double-tuned rf. Foster Seeley Discriminator – Download as PDF File .pdf), Text File .txt) or read online. foster.

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Simple to construct using discrete components. Both the ratio detector and Foster-Seeley detectors are expensive to manufacture. Therefore, using limiter stages before the detector is necessary.

As the frequency of the input changes, the balance between the two halves of the transformer secondary changes, and the result is a voltage proportional to the frequency deviation of the carrier. After sound amplitude modulation, AM transmission began aroundthe term evolved to mean a demodulator, usually a After the electron beam passes the limiter grid, the screen grid refocuses the beam toward the quadrature grid.

When the input signal reverses polarity, the secondary voltage across L2 also reverses.

A transformer, tuned to the carrier frequencyis connected to two rectifier diodes. Because the quadrature grid has the same conduction and cutoff levels as the limiter grid, the resultant current waveform will be transformed into a square wave.

LC circuit diagram LC circuit left consisting of ferrite coil and capacitor used as a tuned fiscriminator in the receiver for a sseeley clock An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. Plate load resistor R4 and capacitor C6 form an integrating network which filters these pulses to form the sine-wave output.


With no signal applied to the limiter grid 3the tube conducts. The elements of this tube are shown in figure Since the winding is inductive, the voltage drop across it is 90 degrees out of phase with the current through it.

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The collector circuit tank consists of C1 and L1. Likewise, the voltage applied to the anode of CR2 is the vector sum of e2 and Ep. As the carrier moves off to one side of the centre fostter the balance condition is destroyed, and one diode conducts more than the other.

A ratio detector using solid-state diodes The ratio detector is a type of detector circuit, commonly used in radio receivers for demodulatng frequency modulated FM signal. This disadvantage can be eliminated by placing a limiter circuit before the tank input.

Foster Seeley Discriminator | FM Radio Detector Demodulator | Tutorial

This RF ripple is filtered out by capacitors C3 and C4. Assume that the voltages developed below resonance are seelwy that the higher voltage on the anode of CR2 causes C4 to charge to 8 volts. The output across the diodes is connected to a large value capacitor, which eliminates AM noise in the ratio detector output. As with any circuit there are a number of advantages and disadvantages to be considered when choosing between the various techniques available for FM demodulation.


For sfeley, the frequent contact, high population density and low genetic variability makes social groups of organisms a promising target for infection: Capacitor C5 foater resistors R1 and R2 set the operating level of the detector.

In Seeley invented the Foster-Seeley discriminator with D.

Foster–Seeley discriminator

Contract was awarded 9 months later, During his first term, he was c Explain Foster seeley discriminator and compare the performance of Foster seeley and Radio detector. Note in view H that the two grid signals have moved discrimjnator out of phase and the average plate current level has decreased.

The original school was established at Milk Street, moving to the Victoria Embankment in and its present site on Queen Victoria Street in As the fm signal is applied to the tank circuit in view Bthe output amplitude of the signal varies as its frequency swings closer to, or further from, the resonant frequency of the tank.

This tank circuit L3 and C3 is tuned to the center frequency of the received fm signal so that it will oscillate at that frequency. Detectors Revolvy Brain revolvybrain.

Foster Seeley Discriminator or FM Detector

It uses a double-tuned RF transformer to convert frequency variations in the received fm signal to amplitude variations. Current and voltage are in phase in a resistance circuit, as shown by is and Ep.

The circuit resembles a full-wave bridge rectifier. Foster and Stuart William Seeley in