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Are audio cassettes FM or AM?

Neither, there is no modulation involved. The magnetization on the media is directly (and hopefully fairly linearly) related to the waveform amplitude. There is a high frequency bias signal added to ...
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  • 5,501
41 votes

How exactly does AM/FM carry both pitch and loudness of voice?

Voice has both pitch, i.e. frequency, and loudness, which are two separate analog data streams. No. Voice is transmitted initially as one analog 'stream' of sound pressure waves in which the air ...
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  • 161k
29 votes

Are audio cassettes FM or AM?

It is neither, the signal is recorded as a magnetized pattern without any form of modulation. This can give an impression of how that works: I got that from here. See, no modulation needed, the ...
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26 votes

How exactly does AM/FM carry both pitch and loudness of voice?

Forget about radio — how do you think voice is transmitted over a wire, which only has "voltage" — again, a single variable? The point is, "pitch" and "amplitude" are abstract parameters ...
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  • 165k
21 votes

If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

The frequency you tune to is the centre frequency of the spectrum created by the modulation. The input from the aerial is generally modulated down to an intermediate frequency (to make it easier to ...
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20 votes
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If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

That "fixed frequency like 103.2Mhz" is a bit of a lie: the radio is tuned to receive a signal in a small frequency band, which width is matched to the modulation depth (variation in the transmitted ...
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20 votes

Why do FM radio signals occupy greater bandwidth than AM?

They need not, narrowband FM occupies the same bandwidth as AM, for the same audio bandwidth. Transmitted AM bandwidth is fixed at twice the audio bandwidth. However, wide deviation FM provides ...
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  • 144k
12 votes

If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

For FM, Carson's bandwidth rule informs you the approximate bandwidth of a transmission. The bandwidth value it calculates contains 98% of the energy of the whole transmission. It is expressed by the ...
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  • 390k
12 votes

How exactly does AM/FM carry both pitch and loudness of voice?

Sound is just a single-dimensional time-varying signal. Microphones essentially continuously track variations in air pressure. At any point in time, this is a single value. This value is what gets '...
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12 votes

Are audio cassettes FM or AM?

Analog tape recording for audio cassette doesnt require modulation. But since magnetization ability of the particles on the tape does not have linear response at low signal levels of the audio to be ...
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10 votes
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Does amplitude of FM signal even matter?

Well it does matter a lot actually. The only difference between a mathematician and an engineer is that the former would say: "Yes, at 0 amplitude there will be no signal" while the latter would say (...
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9 votes
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simplest FM radio receiver?

For a totally passive FM set you can use something like a resonant circuit that is tuned somewhat off the carrier frequency so variations in carrier frequency result in changes in output voltage from ...
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8 votes
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Frequency spacing and the doppler effect

When moving at 1km per second (very fast for anything using a road) a radio wave of carrier frequency 100 MHz will appear to shift to 99.9997MHz if traveling away from the source of the transmission. ...
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  • 390k
8 votes

Radio Transmitter Circuit

Back-story Internally to the BJT is a parasite called "Miller capacitance". It can be regarded as a capacitor between collector and base and is typically, for normal transistors, in the region of 10 ...
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  • 390k
8 votes
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My FM transmitter never works, Why?

Forget building this on a breadboard. The oscillator can't work on a breadboard. Breadboards have capacitance between the pin rows that's about the size of the capacitors in the oscillator. ...
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7 votes
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Basic FM circuit

C3 turns the circuit into an oscillator. To understand this you need to think hard about the role of the emitter and the thing you have to think hard about is this - the emitter (as well as the base) ...
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  • 390k
7 votes
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Would you explain the output waveform of this FM transmitter circuit?

Why someone hasn't answered this beats me.... Your sound card input is good for 20 kHz and maybe 80 kHz on a good sound card sampling at 196 kHz. 88 MHz is well over a thousand times too high in ...
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  • 390k
7 votes

Identifying an old RF circuit

It looks like an RF transmitter to me, maybe FM It smells of amplitude modulation rather than FM because of the way 2 modulates the base bias in the oscillator. Moreover, I'm puzzled by the ...
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  • 390k
7 votes
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Identifying an old RF circuit

It's Citizen's Band (about 27MHz) AM transmitter which sends a dual frequency tone - maybe it's intended to activate or turn off some machine. The crystal stabilizes the frequency, it cannot be FM. ...
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6 votes
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How to build an FM transmitter and how does it work?

How am I supposed to learn this stuff? There are no short cuts and I would learn the following (but there's no guarantee I haven't missed anything from the list because I learnt this stuff decades ...
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  • 390k
6 votes

FM transmitter design?

L1 and C4 are the parallel-resonant tank circuit for the RF oscillator, and Q1 is wired as a common-base amplifier that provides the gain required for oscillation, with the feedback (and output ...
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  • 165k
6 votes
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FM transmitter design?

This is a variation on a Colpitt's oscillator. L1 and C4 make up the main LC resonant circuit. C5 is used to provide feedback to the emitter of the transistor which amplifies the signal and makes up ...
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  • 29.8k
6 votes

Building an fm transmitter broadcasting simultaneously to all fm frequencies

In days long ago, this was done by transmitting a strong signal at the IF frequency of 10.7 MHz. Most radios in that era did not have sufficient shielding in the IF section and this signal was ...
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  • 22.7k
6 votes

I supplied 220 volts to 120 volts FM radio receiver?

Excuse me for this slightly sarcastic comment, but: No, you cannot revive your radio parrot: Well, you connected something to a voltage supply twice as high as it was meant to be used with. If you'...
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6 votes

How exactly does AM/FM carry both pitch and loudness of voice?

Voice has both pitch, i.e. frequency, and loudness, which are two separate analog data streams. There's more than two, depending entirely on how you perceive/analyze it, and what else is going on, on ...
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6 votes
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Why can't we divide the electromagnetic spectrum into arbitrarily many radio frequency bands?

Signals don't exist at a single frequency. They have a bandwidth that spreads across spectrum. The radio station at 101.7MHz takes up the spectrum from 101.6-101.8MHz.
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6 votes
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Does satellite radio use AM or FM or both?

Neither. Satellite radio such as Sirius transmits the digital data with COFDM-DQPSK modulation.
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  • 93k
5 votes
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What is this type of radio fm antenna connector called?

Assuming the ruler is showing millimeters, I'd say that the connector is of JST-XH-2.5 mm type with two pins. Sometimes, these connectors are sold and marked with 2.54 mm in their name, since that is ...
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  • 22.8k
5 votes
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FM Carrier Wave Generation

Q2 and the circuit around it form a Colpitts oscillator. This makes use of the fact that a transistor in the common base configuration can have voltage gain from emitter to collector. Consider this ...
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