71 votes
Accepted

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 ...
Phil G's user avatar
  • 5,659
42 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 ...
Transistor's user avatar
  • 176k
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 ...
Bimpelrekkie's user avatar
  • 80.9k
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 ...
Dave Tweed's user avatar
  • 173k
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 ...
Neil_UK's user avatar
  • 167k
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 '...
alex.forencich's user avatar
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 ...
soosai steven's user avatar
10 votes
Accepted

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 ...
Spehro Pefhany's user avatar
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 ...
Andy aka's user avatar
  • 457k
8 votes
Accepted

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. ...
JRE's user avatar
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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 ...
Andy aka's user avatar
  • 457k
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'...
Marcus Müller's user avatar
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 ...
Harper - Reinstate Monica's user avatar
6 votes
Accepted

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.
Charles H's user avatar
  • 206
6 votes
Accepted

Does satellite radio use AM or FM or both?

Neither. Satellite radio such as Sirius transmits the digital data with COFDM-DQPSK modulation.
Justme's user avatar
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6 votes
Accepted

Broadcast FM: Where is the pre-emphasis applied?

The recommendation how it should be done is stated in ITU-R BS.450-4, "Transmission standards for FM sound broadcasting at VHF". I know I've seen a better document with block diagrams but it ...
Justme's user avatar
  • 149k
6 votes

What is this circuit? (FM detector?) - LTspice

First put in the right diode model for the diode you have into SPICE. If you want to find the resonant point, it would be at the point I have labeled RP (which is a resonator attached to a rectifier ...
Voltage Spike's user avatar
  • 82.7k
5 votes

Select Phase Detector Cutoff Frequency? Phase Locked Loop FM Demodulation

When building a phase locked loop, the purpose of the low pass filter is poorly understood. When you wrap a phase feedback loop around a VCO, the integration of frequency to phase causes a 20dB per ...
Neil_UK's user avatar
  • 167k
5 votes

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

In a simple AM system, the transmitted signal is something like $$x(t) = A\left(1+m(t)\right) \sin\omega_c t$$ and \$m(t)\$ is called the message signal. In an AM radio, the message signal ...
The Photon's user avatar
  • 130k
5 votes

Broadcast range of an FM radio station with given transmit power

OK lets provide a line-of-sight non-multi-path (no reflected energy that may cause peaking and nulling, as airplanes may do, or large drones may cause) link analysis. Assume: you want good FM audio, ...
analogsystemsrf's user avatar
5 votes
Accepted

Understanding this simple FM receiver

The inductor L, the capacitor C and multiple (intrinsic) capacitances of the transistors form an parallel LC-tank circuit with resonance frequency of about 100MHz. The trim-capacitor C allows tuning ...
Stefan Wyss's user avatar
  • 7,430
5 votes
Accepted

FM broadcasting text

It is implemented using the so called Radio Data System (RDS). Which transmits the channel name, current song and more on a 57 kHz subcarrier. Source: https://en.m.wikipedia.org/wiki/...
Jakob Halskov's user avatar
5 votes
Accepted

Why can FM be demodulated non-coherently while PM cannot be demodulated non-coherently?

The phase of a signal is only defined with respect to a reference. If the reference cannot be communicated, then the phase is meaningless. Often when phase modulation is used, it's treated as ...
Neil_UK's user avatar
  • 167k
4 votes

Can a filter circuit be built for the FM broadcast range to only pass the frequencies not bearing a broadcast stream?

Of course it can. What you need to do is to perform a band scan and look at signal strengths. If you plot it, you would get something like this: If the signal is above a certain threshold, some ...
Armandas's user avatar
  • 7,915
4 votes

Send text data using FM frequencies

You can use basic radio modules like these: - These happen to be from a company called RF solutions but there are plenty of people supplying them. The tricky part is packaging the data (that you ...
Andy aka's user avatar
  • 457k
4 votes

Piece of wire as FM antenna

Have you recently plugged in a phone charger close to the radio? @andy_aka You were spot on. Moving the USB phone charger to the other side of the room has eliminated the interference. I think ...
Andy aka's user avatar
  • 457k
4 votes
Accepted

RDA5807M FM antenna question

F1 and F2 are inductors that are designed to have relatively high impedance at VHF .This is to stop valuable RF signal being wasted .It also stops RF getting into the AF output pins of the chip .If ...
Autistic's user avatar
  • 14.7k

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