What is a product detector?

It uses a mixing process with a locally generated carrier.

From gconklin:

The product detector is the circuit used to combine the signals from the intermediate frequency (IF) amplifier and beat frequency oscillator (BFO).

The product detector is a type of frequency mixer that acts as a demodulator for SSB signals. The result is then sent to the audio frequency (AF) amplifier in the single-sideband receiver.

See Wikipedia's article on Product detector

Also, see the Electronics Notes site for the article on AM Demodulation: Amplitude Modulation Detection

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Which circuit is used to detect FM-phone signals?

Frequency discriminator.

From wp2ahg:

Balanced Modulators create double side band AM.

A FREQUENCY Discriminator is used to detect FREQUENCY Modulated phone signals,

Product Detectors are for SSB and AM

Phase Splitters separate signals into multiple phases.

Please see Wikipedia for the article on Frequency Modulation and the article on Detector.

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What is the process of detection in a radio diode detector circuit?

Rectification and filtering of RF.

From papusa and kg5kou:

Source: The Electronics Notes site, article Diode Detector: AM Diode Envelope Demodulator

"A Diode Detector is the simplest way of demodulating AM signals. It operates by detecting the envelope of the incoming signal which it does by rectifying the signal.

Current is allowed to flow through the diode in only one direction, giving either the positive or negative half of the envelope at the output.

The AM detector or demodulator includes a capacitor at the output. Its purpose is to remove any radio frequency components of the signal at the output (Read Filtering). The value is chosen so that it does not affect the audio base-band signal."

Hint: Remember Rectification

Please see the Analog Devices site for the article Understanding, Operating, and Interfacing to Integrated Diode-Based RF Detectors

See also the Electronics Notes site for the article Diode Detector: AM Diode Envelope Demodulator

And, see the Analog site for the pdf document titled RFI Rectification Concepts

See Wikipedia's articles on Detector (radio) and also the article on the Rectifier

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What is a frequency discriminator in a radio receiver?

A circuit for detecting FM signals.

From rogress:

FM stands for Frequency Modulation and is a method of sending an audio signal by modulating the frequency of the signal. In order to convert that signal back to regular audio the receiver needs something that can discriminate (or detect) the changes in frequency.

Thus, the circuit that detects the FM signals is called a Frequency Discriminator (or sometimes Frequency Detector).

Source: Wikipedia

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In a CTCSS controlled FM receiver, the CTCSS tone is filtered out after the:

Discriminator but before the audio section.

Please see the Repeater Builder site for the article A Historical and Technical Overview of Tone Squelch Systems

Also, see Wikipedia's article on Continuous Tone-Coded Squelch System

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What is the definition of detection in a radio receiver?

The recovery of intelligence from the modulated RF signal.

See Wikipedia's article on Detector and the article on Radio receiver

Also, see the Electronics Notes site on the article AM Demodulation: Amplitude Modulation Detection and the article on Diode Detector: AM Diode Envelope Demodulator

And, view the pdf document from the USNA Edu site called Lesson 18: Intro to Modulation

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