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Questions tagged [fm]

For questions relating to frequency modulation (FM). This is a scheme where a carrier is modulated by varying its frequency to carry information.

8
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3answers
2k views

Are audio cassettes FM or AM?

I know that cassettes store an analog signal, but is the signal Amplitude-Modulated (AM) or Frequency Modulated (FM)?
2
votes
2answers
121 views

Is it possible to broadcast FM radio up to 500 metres? [on hold]

I'm buying FM transmitter 0.2 watt at Lazada to broadcast for my village community at my area. Not a normal small FM transmitter for car or portable low watt (about 10mW-100mW) which broadcast up to ...
1
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0answers
42 views

FM Radio Transmitter and Receiver Design

We have a project to design a wireless full duplex intercom circuit using frequency modulation technique. I've searched the web for designs and I have come up with these: Low Power FM Transmitter ...
20
votes
10answers
6k views

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

Almost every tutorial on AM/FM modulation shows the modulating signal as something like a simple tone or continuous sine wave. Now that's easy, and for AM you just superimpose the modulating signal ...
2
votes
2answers
92 views

Using audio instrument cable for 1MHz transmission

I'd like to transmit digital data together with an audio signal along an instrument cable. In more detail, I'd like to send MIDI data and the audio signal of a guitar on a single cable. The rationale ...
0
votes
0answers
39 views

Derive required carrier to noise or signal to noise from receiver sensitivity on FM receiver

Can I extrapolate the required C/N based on reported receiver sensitivity? I'm plotting coverage for a repeated radio system for handheld radios. The system is analog, FM narrow band. I've ...
-2
votes
3answers
170 views

Radio Transmitter Circuit [closed]

I have seen previous similar answers about radio transmission, but looking at the following scheme I am not sure about the role C3 plays in the circuit. I guess it is needed to remove the DC signal ...
9
votes
2answers
553 views

Identifying an old RF circuit

I got an old RF circuit (I guess), probably used for pedagogical purposes. Here's the schematic: I chose the positive and ground rails as it seems right to me, looking at transistors and resistor ...
1
vote
2answers
78 views

Understanding PLL performance: PFD output bandwidth

For an application I need to FM modulate a signal with a 10 MHz bandwidth. Due to constraints I have no control over, I have to do it in an analog way (so I can't just digitize the signal, IQ modulate,...
0
votes
1answer
35 views

Amplitude Spectrum of FM wave from Bessel First order

given the values for \$\beta=5\$, for the Bessel of the first order: \$ J_{0}(5)=-0.26, J_{1}(5)=0.34, J_{2}(5)=0.49...\$ in order to plot the amplitude spectrum of the FM wave, do you treat the ...
1
vote
1answer
52 views

how to calculate the maximum radiated power for the FM broadcasting?

I am trying to experiment a fm transmitter project of Raspberry Pi - with a frequency of 88.1 MHz. http://icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter However, I ...
1
vote
0answers
75 views

Phase Locked Loop Gain Design- FM Demodulation

Say I am trying to demodulate a message up to 25kHz in frequency, with a peak frequency deviation of 75kHz and a carrier of 1MHz, implying a 200kHz bandwidth using carsons rule. Would I design the ...
2
votes
2answers
75 views

Select Phase Detector Cutoff Frequency? Phase Locked Loop FM Demodulation

I'm studying a Phase Locked Loop used for FM demodulation, obviously a phase detector is used in the system. A basic implementation of a phase detector is a multiplier followed by a lowpass filter. I ...
2
votes
0answers
101 views

Matlab Phase Locked Loop Design : FM Demodulation

EDIT: It seems I've asked too much at once here. I'll do some more studying and come back if I have more specific questions. I'm trying to design an analog phase locked loop in Matlab. I've read ...
2
votes
2answers
63 views

Does the remote car door keyfob in today's automobiles change its code with every use?

I am just wondering why other keyfobs do not open my car door and thought every signal would have to be unique. So I did some research and they use a rolling code so in fact the code changes with ...
1
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3answers
178 views

FM transmitter circuit working?

I am trying to understand FM transmitter circuit working basically on how a signal is imposed on to the carrier signal. I would like to get an acknowledgement on whether my understanding is correct or ...
0
votes
1answer
188 views

Best mixer for quadrature FM demodulator

I need to demodulate an FM signal and I want to use a quadrature demodulator for this. The signal is 16±0.15 MHz, 3.3V output from CMOS oscillator. I know that Gilbert cell mixers are most commonly ...
0
votes
1answer
119 views

Choosing the best FM demodulation technique

I have an FM signal: 200 mVpp, 11.5 MHz carrier, max deviation - 500 kHz, modulating signal frequency range is 40-10000 Hz. And I need to demodulate it with highest SNR possible. The circuit has to ...
0
votes
0answers
115 views

Keeping constant bandwidth in tunable quadrature FM demodulator

I need to demodulate an FM signal (4 MHz max deviation) with a strong center frequency drift (550-800 MHz). I've built an AFC circuit to track the drift and now I need to build a tunable quadrature ...
0
votes
0answers
41 views

Operation of simple FM transmitter circuit [duplicate]

I found the following little FM transmitter circuit among some old papers and it works pretty well, but I have a tough time understanding how the circuit operates: I understand the trimcap and ...
0
votes
1answer
44 views

SA605 input impedance

I am trying to find the associated input impedance to the SA605 mixer RF inputs. I have found several App notes associated with the Chip that discusses the design. On the datasheet they present the ...
1
vote
2answers
111 views

FM preselect filter

Hello I am designing an fm receiver and had some questions about the RF front end. To tune into different channels I know I need a tunable oscillator, but does the bandpass filter connected to the ...
0
votes
2answers
76 views

FM radio Interference

Near to my location we have IAF(Indian Air Force - Tambaram) training center is there, While hearing FM radio at a at frequency of 106.4MHZ I can hear the cockpit commands/voices daily when these ...
1
vote
1answer
54 views

FM folded dipole Antenna

I am designing my personal FM receiver, and I have a question regarding how to design my Antenna, in terms of choosing the wavelength to determine the size of the antenna. To put it as simple as ...
1
vote
2answers
157 views

Could a vintage 9 transistor AM/FM implement a phase-locked loop of some form?

A side discussion around an answer to the question How many stations could one hear with an AM/FM radio in front of the ISS' cupola window? has arisen with regard to the possibility that a change in ...
0
votes
2answers
573 views

FM Transmitter Power and approx Transmission Distance Calculation [closed]

I am a beginner of electronics and mostly fascinated by hobby circuits right now. I do not have any Electronics Degree. Internet and hobby Electronics books are the only places where I learned lill-...
0
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2answers
601 views

FM modulation with crystal oscillator [closed]

I have seen many posts where a simple AM transmitter can be made with a crystal oscillator and modulation transformer. Can this idea somehow be modified to FM. I don't want people to misunderstand me. ...
0
votes
1answer
212 views

DIY FM Transmitter [closed]

simulate this circuit – Schematic created using CircuitLab I can not find the frequency from an FM receiver... I am not sure for the coils Henries... I tried to make on of my own and I used: 19 ...
1
vote
0answers
157 views

What is the current status of RDS 2.0?

Radio data system is the standard used for embedding small digital information in FM radio. I am excited for the release of the new RDS 2.0 standard. But I am not really sure if the technical standard ...
1
vote
2answers
428 views

“Old FM” vs. Modern FM radio signal. What's the difference and can I adapt?

I have a vintage radio that I managed to get all circuits and tubes back into original spec. The AM stations tune in fine but I get nothing on FM. I am told this is because it's tuning in "Old FM" - ...
-1
votes
2answers
746 views

FM Receiver, RF Amplifier

In the previous FM receiver, how does the left transistor amplify the input radio signal from the antenna at the collector and output it at the base, from what i know the base always has a smaller ...
1
vote
1answer
219 views

FM Tansmitter - AC Equivalent Circuit - Capacitor Analysis

This is a follow on question from the following two questions: Operation of LC circuit in Frequency Modulation with simulation and linking it to the basic principle of frequency modulation How to ...
0
votes
1answer
146 views

FM Transmitter Circuit Range

I have connected the previous circuit, it transmits a clear sound with almost no distortions but the range is awful, How can i improve its range?
0
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2answers
100 views

Datasheet FM Modulator

Hi I want to implement a narrowband FM transmitter and I find all features about power and noise in the FM Modulator datasheet, but nothing about bandwidth. The transmitter will work at center RF ...
0
votes
0answers
74 views

Max Output Voltage Preamplifier Microphone

I'm looking a preamplifier to get 1-2 Volt as Maximum Output Voltage of a microphone with jack 3.5 mm. To get a line-in signal and then modulate in FM. I don't know if this I've found works. Beh­...
0
votes
0answers
64 views

FM RDS Sensitivity

I am planning to build a clock based on FM RDS stream. I don't like to have external antennas and furthermore, FM reception in my bedroom is not very good. My hope is that RDS data bitrate is very low ...
7
votes
1answer
2k views

Why do FM radio signals occupy greater bandwidth than AM?

If a 5kHz baseband signal is modulating an AM carrier wave, the sidebands will be centered around the carrier wave and the the signal will occupy 10kHz bandwidth. AM radio limits the upper modulating ...
0
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0answers
46 views

Antenna cable pin-out identification

I am trying to connect a stock car FM/AM antenna with a new aftermarket stereo system, Turns out my car antenna has 2 wires. One is Co-axial cable for signal (Most probably) and there's one more ...
5
votes
2answers
178 views

Can AM and FM signals at the same frequency be separated?

Suppose one radio station emits an amplitude modulated (AM) signal at 100 MHz, and a nearby station emits a frequency modulated (FM) signal at 100 MHz. Is it possible to separate these two signals, ...
0
votes
1answer
200 views

What does “a 40 kHz wave modulate with a 1 kHz sound” mean? [closed]

what is mean when say "a 40 kHz wave modulate with a 1 kHz sound"? which of AM or FM Modulation means?
0
votes
1answer
64 views

A trio of questions about radio/smartphones [closed]

I know that smartphones can receive FM radio using earbud/built-in antennas, but can they receive amateur radio frequencies (144 MHZ?) and if so, how? Is there a way to sending out radio waves and ...
0
votes
0answers
115 views

Why does a foster seeley circuit need transformer coupling?

Having read most of the online references to this circuit and performed some simulations, I still don't have a firm grasp on how this circuit functions. Here's a schematic to refresh (possibly ...
2
votes
1answer
228 views

Frequency changing element in an FM transmitter

In a simple FM transmitter such as this What element does the frequency modulation? I don't mean the oscillation itself, since it's clearly created by tuned tank circuit, but the modulation. There ...
0
votes
0answers
160 views

Phase Modulator with JFET

At the university we have seen this circuit as a Phase Modulator: simulate this circuit – Schematic created using CircuitLab where \$m(t)\$ is the message at audio frequency and \$v_p(t)\$ is ...
0
votes
1answer
3k views

Relation between Signal to Noise Ratio (SNR) and Transmission Bandwidth for FM signal

I was encountered by the below question :: ...
-3
votes
2answers
1k views

How does the LC circuit work in a FM transmitter circuit

I am using a app called Every Circuit. I dont understand how does the LC circuit function i know that it produces a sine wave but in that case both side of the lC circuit capacitor are connected at ...
0
votes
1answer
473 views

How does the frequency increase and decrease in a FM transmitter circuit?

i still dont understand how fm transmitter circuit works, from what i understand the transistor acts like a switch or a valve when the output voltage increases and decreases wont it affect the ...
-3
votes
1answer
179 views

Simplest FM Radio Spectrum Capture Hardware Without Demodulation [closed]

I am trying to build a FM receiver circuit with simplest elements, transistors, capacitors (an op-amp such as LM 741 would be fine too) for analysis purposes (not real-time radio). The circuit should ...
0
votes
0answers
118 views

Fundamentally utility of sidebands FM

In my course of telecommunication they're talking about Frequency Modulation with the mathematical working-out of the Bessel-graph, but it's not clear enough to understand the goal. First we've looked ...
0
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1answer
397 views

Is FM index affected by frequency multiplication?

I came across this question which goes An FM signal with modulation index mf is passed through a frequency tripler. What will be the modulation index at the output of the tripler? and according to ...