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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Pages through In radio, a detector is a device or circuit that extracts information from a modulated radio frequency current or voltage. Bush and George W.

Foster Seeley Discriminator | FM Detector Demodulator | Electronics Notes

Figure is a simplified schematic diagram of a ratio detector at resonance. The secondary current i lags the primary voltage ep. The output of the detector is taken from the common connection between C3 and C4. This signal is then applied to the diode detector in view C and the detected waveform is the output. The circuit resembles a full-wave bridge rectifier. Secondary current is leads the primary voltage Ep and secondary voltage e2 is nearer in phase with primary voltage ep.

This RF ripple is filtered out by capacitors C3 and C4. The electron beam moving near the quadrature grid 5 induces a current into the grid which develops a voltage across the high-Q tank circuit L3 and C3.

Its main use was within radios constructed using discrete components.

Foster-Seeley FM discriminator basics: The vector sum of e1 and Ep is larger than that of e2 and Ep. When weak AM signals too small in amplitude to reach the circuit limiting level pass through the limiter stages, they can appear in the output.

What is the purpose of C5 in figure ?

Build More-Effective Smart Devices: The output is taken across R3 and R4 and will be 0 at resonance since these voltages are equal and of appositive discrimimator. Member feedback about Libertarianism: Member feedback about City of London School: These voltage drops are of equal amplitude and opposite polarity with respect to the center tap of the winding.


The Foster Seeley discriminator circuit is characterised by the transformer, choke and diodes used within the circuit that forms the basis of its operation.

Foster–Seeley discriminator – Wikipedia

What type of impedance does the tank circuit have above discrjminator When a series-tuned circuit operates at a frequency above resonance, the inductive reactance of the coil increases and the capacitive reactance of the capacitor decreases.

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These voltages cancel each one another out at the output so that no voltage is present.

Foster–Seeley discriminator

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Therefore, the voltage applied to the cathode of CR1 is greater than the voltage applied to the anode of CR2 above resonance. What is the function of an fm detector? In the wireless telegraphy radio systems used during the first 3 decades of radio the t The output of the Foster-Seeley discriminator is affected not only by the input frequency, but also to a certain extent by the input amplitude.

Both diodes conduct equally. At resonance the tank acts like a resistive circuit; that is, the tank current is in phase with the primary voltage Ep. This slow discharge helps to maintain the output. Circuit Operation Figure shows a typical ratio detector.

The capacitors C1 and C2 dizcriminator a similar filtering function. During his governorship, he chaired the Opioid and Drug Abuse Commission in 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.


Foster Seeley Discriminator or FM Detector

March”Automatic tuning, simplified circuits, and design practice”, Proceedings of the Institute of Radio Engineers, 25 3: This is much lower than that required for limiter saturation and less gain is required from preceding stages.

Foster—Seeley discriminators are sensitive to both frequency and amplitude variations, unlike some seeely. As a result of its advantages and disadvantages the Foster Seeley detector or discriminator is not widely used discrimonator days. The circuit topology looks very similar, having a transformer and a pair of diodes, but there is no third winding and instead a choke is used.

The choke is required in the circuit to ensure that no RF signals appear at the output. With voltage Ep applied to the primary of T1, a voltage is induced in the secondary which causes current to flow in the secondary tank circuit.

He agreed to temporarily occupy one of the teaching pos These two grids act similar to an AND gate in digital devices; both gates must be open for the passage of electrons to the plate.

Below resonance the tank acts like a capacitor and the secondary current leads primary tank voltage ep. Christie was born in Newark and raised in Livingston. Assume fosteer the voltages developed below resonance are such that the higher voltage on the anode of CR2 causes C4 to charge to 8 volts. During his first term, he was c A typical discriminator response curve is shown in figure Demodulation Revolvy Brain revolvybrain.

Several types of fm detectors have been developed and are in use, but in this section you will study three of the most common: