Questions tagged [frequency-modulation]
For questions relating to frequency modulation (FM). This is a scheme where a carrier is modulated by varying its frequency to carry information.
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Demodulation of FM signal frequency
After playing with homemade AM radios, I noticed that it is boring to broadcast AM signals all alone. I have also noticed that the AM stations around us, are so limited that I had no other chance than ...
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What is a modulated optical sensor?
I was told to try out a modulated optical sensor as a better and more "robust" option than the usual (unmodulated) optical sensors, saying the modulated ones are less subject to interference....
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Spectrum of FM signal?
If a carrier (\$f_c\$) is FM modulated by a single sine wave (\$f_m\$), its spectrum is composed of frequencies at \$f_c + kf_m\$ (\$k \in \mathbb{Z}\$) whose amplitudes are weighted by \$J_n(\beta)\$,...
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Band selection circuit for SI4825 A10
Following the official schematic and guideline (AN738: Si4825/36-A
Antenna, Schematic, Layout, and Design Guidelines), I am building a Si825 A10-based radio receiver.
I am getting weak audio output ...
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How to measure FM deviation for pilot signal?
I'm trying to calibrate my FM signal generator, but don't have the required FM detector. The instructions say:
Turn pilot ON, comp OFF
Set pilot to 10% deviation
Verify detector says 7.5kHz, or ...
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Which one of these transistors is equivalent to 2N918 NPN?
This is an FM radio receiver. Q1 is 2N918 NPN transistor but it is not available for me.
Which one of the following transistors is more equivalent to Q1 ?
BC547
TL431
s8550
s9014
2n5401
2n5551
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What can be done to increase the dynamic range of a FM receiver?
If i have to receive a signal from a far away FM station, nearby stations swamp the receiver if they are both nearby physically or nearby in the spectrum. I believe the AGC in my radio is cutting out ...
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What could be blocking communication with TDA7706S on a Sony GT520U radio?
I have a Sony GT520U radio which started developing a lot of noise and becoming unresponsive when in tuner mode. Opening it revealed the chipset on the tuner was overheating in less than 3 minutes of ...
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SIMULINK: The spectrum of the modulated signal remains unchanged despite modification of the modulation index
I try to implement a frequency modulator.
From what I know, the more I vary the modulation index (which is set by the gain block here,) the more the spectral lines should increase in number.
When I ...
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Frequency upconversion from 1 to 100 MHz for FM transmitter
I'm trying to build an FM transmitter like pifm but using the ESP32. I can generate an FM signal at the DAC output of the ESP32 with a carrier frequency of 1 MHz and a deviation of 25 kHz, but in ...
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How to make very low range FM Transmitter?
I am experimenting with building an FM transmitter. I want to make it only have a range of a few meters so I can detect it on my radio at home at a distance of a few meters. The circuit diagram is ...
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Simple detection of a transient FM frequency shift
I have an application with a 2D array of inductive sensors for position detection of an object on a plane. I have experimented with inductance to digital converters (https://www.ti.com/product/LDC1314)...
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FM receiver with 2N3904
Please explain how these 2 transistors work.
I don't understand how it active an amplify the signal.
Source: https://circuitdigest.com/electronic-circuits/simple-diy-fm-receiver-circuit-on-internet
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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 ...
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FM transmitter not giving the intended output of 88MHz to 108MHz
I am trying to build an FM transmitter that outputs 88MHz to 108MHz range using Multisim, but the circuit I constructed gives a lower voltage and lower frequency at the output according to the ...
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Modern approach of creating VHF FSK (FM) recieeiver
I need to make a narrow band FM receiver for the VHF band. More specifically, not even FM, but FSK. The operating frequency range should include from 35 to 40 MHz. Frequency deviation is around 0.5 to ...
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Antenna tuner for 1MHz to 150MHz
I am trying to build an antenna tuner for my 2m (1m + 1m) dipole antenna. It has a 1:1 balun and is connected to a coaxial cable which is connected to my radio with an impedance of 50 ohm. I can't ...
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Broadcast FM: Where is the pre-emphasis applied?
A DSP guy like me should know this, and I think that I do, but I can't seem to find a definitive answer in my Carlson Communications Systems textbook.
We know that FM is like phase-modulation (PM) but ...
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How phase is modulated according to our message signal?
My question: let message signal m(t) be sin(w1t).For frequency modulation (instantaneous phase deviation=phi(t)) d[phi(t)]/dt=kf m(t) so i get that at 90° or π/2 frequency will be max because the ...
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Why does the frequency deviation of a FM wave have different definitions?
Source 1 defines the modulation index in the expression for FM as follows:
As per the expression for frequency modulated wave, isn't the frequency deviation same as Modulation index 'M'?
"The ...
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Why is my LC oscillator PCB design not working?
I'm building a simple FM transmitter to learn more about LC oscillators. I've successfully designed and built the following transmitter on a bread-board and perf-board using standard through hole ...
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IQ data for analog FM modulation
I am trying to understand how I can produce analog FM modulation using IQ data.
So far, I know to generate the FM modulation with an IQ modulator (like the LTC5599.) I have to apply IQ data in ...
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STM32 FM Transmitter using PWM limitations?
As a learning experiment, I am trying to use PWM to transmit audio in the FM band (80MHZ - 108Mhz).
Currently, I have a PWM output with a prescaler of 0, ARR of 1, and pulse width of 1. Since I'm ...
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AM Receiver Antenna Coil
In almost all the radio receivers whether FM or AM, custom wire-wound coils are used that are wrapped on a ferrite core usually (not always) of 100 mm x 10 mm dimensions. Is it possible to use fixed ...
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How to adapt a FM reciever circuit to use a varicap diode instead of a trimmer capacitor
My team and I are interested in learning about FM communication and decided to build a simple FM receiver before building a proper transmitter. We looked at some circuits on the web, and they all seem ...
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Weird component in radio player interferes with FM functionality of the radio itself
I got my hands on an old radio player which has both cassette player and FM/AM functionality. I got constant noises while playing on FM and it turns out to be some weird component on the cassette ...
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LoRa - Frequency Shift Chirp Modulation - chips in a symbol
I am trying to create a form of FSCM (frequency shift chirp modulation) based on LoRa principle just to learn from it and to obtain a deeper understanding.
What I do not get:
why is (or must be?) the ...
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Modify Si4703 FM Tuner evaluation board to add an external antenna
I have this Si4703 evaluation board which I would like to modify to attach an external antenna. The board usually uses the plugged in headphone cable as the antenna.
Here are the relevant schematics:...
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FM receiver circuit [closed]
I am doing a college project where I have to build an FM receiver.
I didn't have a lot of knowledge about the subject before starting my research. Now, I understand the function of the principal ...
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Discrete component FM radio receiver circuit - explanation needed
I have built an FM radio receiver from a kit. I'm very happy with the results! It is the Sinclair Micro FM.
My goal is to learn about discrete electronics (NO IC's.)
The radio works great, but I ...
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Need help with signal modulation
To capture a mammalian cell, I need to have a constant 4MHz AC signal (coming from a function generator) while sweeping the frequency from the vector network analyzer (VNA) 9kHz to 9GHz to read the ...
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Why doesn't this FM receiver work in LTspice?
After years, I'm back again to the electronic world. To start off, I just tried to simulate this circuit in LTspice:
Source
Here is what I've done in LTspice:
But it doesn't work. Here is a ...
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What is the energy efficiency between FM radio tower broadcasting over an area vs point to point streaming via Internet?
Doing some research, it seems that an FM radio tower in a densely popoulated area can maximally transmit about 50kW of power. If you assume a certain amount of people tuning into the station, is that ...
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Fm receiver local VFO sa615
I'm building a FM receiver based on a SA615.
But when I test the VFO (variable frequency oscillator) with a spectrum analyzer and a sniffer probe I don't see any frequency showing up. So the ...
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Hint for the way a fm receiver works
As far as I know , a simple AM receiver can consist of a LC filter(connected at antenna) which amplifies the selected frequency, a demodulator( a diode for example) which rectifies the signal,an amp ...
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FM Circuit Simulation
I tried to simulate a circuit that I found in google. I adjusted some of the values in the tank circuit but the output waveform resembles that of amplitude modulated wave. What could possibly be wrong ...
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In this Foster Seeley discriminator, what is the purpose of capacitor C3?
I understand the whole circuit, except for the use of capacitor 3. What's its purpose in here?
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Simple schematic for 10.7 MHz crystal-based marker generator
For FM tuner alignment purposes I want to build an outboard 10.7 MHz marker generator to use in association with a piece of gear (ST1000A) that doesn't have one built in. They used to be available in ...
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FM demodulation circuit
I'm doing an FM demodulator circuit. I am copying the circuit from LTspice in the first image) to Multsim (the second image.)
Is what I did in Multisim correct? How can I get a graph from Multisim ...
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What is the method to mute sound during seek on RDA5807 FM?
How to does noise canceling work on thisRDA5807M FM radio module?
What can I do to mute noise on the radio?
I want to mute immediately when there is blank white noise on the FM radio.
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Is it true that frequency deviation over 2*pi is the phase deviation of an FM/PM signal?
for ∆f frequency deviation if for FM only and PM has Phase deviation. and
Kf= ∆f (Hz) of FM? Kf = ∆f (rad/s) for PM?
and for th rules:
∆f=(kfmp)/(2p) for FM where mp = mp max-mp min
∆f=(kfmp)/(2p) ...
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Can the intelligence message of an FM signal be cross-modulated onto another FM signal due to nonlinearities?
Can the intelligence message of an FM signal be cross-modulated onto another FM signal due to non-linearities?
Where I work, we have several FM two way repeater radio sites.
Over the years I've heard ...
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Can telescopic FM/DAB antenna be replaced by Coax?
I tried to search for this prior to asking but with no luck...
I have an FM/DAB+ antenna like this:
from which a standard 75-Ohm Coax is coming down and I would like to connect it to the radio (...
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FM demodulation (not!) using PLL?
I have to demodulate a square wave FM+PWM modulated signal, so for the FM demod I'm using a PLL with a positive edge sensitive comparator to lock on frequency only (CD4046BE). Carrier frequency is ...
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How would a modulated and demodulated signal differ in FM and PM? Simulink Simulation
I am trying to observe the differences of phase and frequency modulation. On the figure below, the left scope shows a frequency modulation and demodulation whereas the right scope shows a phase ...
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FM transmitter won’t work. I need help with more gain, and current at the output
I am trying to make an FM transmitter circuit using cascaded transistors. My two input signals are from a microphone and from an 80 MHz crystal.
I’ve calculated a gain of 22 from the first stage and ...
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Loop Filter in all digital PLL cutoff?
I am implementing an all digital PLL system on an FPGA using VHDL. Now, I have not yet closed the loop, instead I have modelled a sinwave(simulating an input) at 22kHz and also modelled a cosine wave(...
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Controlling DC (Pager) Motor with Audio Signal
I'm trying to control a DC (pager) motor with a sound signal so that I can use an audio synthesizer to control the speed of the motor. I'm hoping to modulate the speed of the motor at audio rate (1-...
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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 ...
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Transmit beeps from Arduino through FM transmitter circuit
I am trying to create a simple Arduino parking sensor that sends the warning beeps to the car radio using FM transmitter circuit.
I searched different FM circuits and found many of them that use a ...
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