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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RF signal on Audio/Music/Guitar equipment
It is looking like the standard RF noise from my (new to me) old apartment wiring through my amp to my speakers. Suspected it could be due to poor guitar shielding/grounding, bad cables etc. Started ...
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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 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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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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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 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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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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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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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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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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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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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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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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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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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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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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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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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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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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Frequency Modulation - Why don't we modulate the carrier by multiplying message signal m(t) directly with f_car?
I am master student of computer science and I have got a problem/question from the domain of communication engineering. So: I'm listening to a lecture that's about Layer 1 stuff, and recently we ...
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Decoding/Demodulating audio data in Patent US4877027A [closed]
I'm interested in decoding/demodulation audio/voice data sent using microwave pulses as described in this patent: US4877027A - Hearing system
In the patent it's shown that voices or any other audio ...
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How decreasing the effective load impedance in the secondary of a transformer heavily dampens it?
I am reading the operation of the ratio detector for FM demodulation. It works on the principle of diode variable damping (please see the figure here). The capacitor C9 restricts the changes in the ...
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Can I use a BC338 in this application?
I want to build this FM transmitter that runs on 1.5-3V.
I've got 2 questions so far:
Can I use a 2N2222A NPN in this application? (I think I can but want to double check.)
How can I calculate (or ...
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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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FM receiver With LM386 - Need a Preamplifier
I am building a hoppy FM Receiver and I created the Preamplifier stage 1 and linked it with the LM386 Stage and it goes OK but The output sound from the Speaker is weak so I tried to do some ...
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What does 'rotating vector addition' mean in this context, and how does it generate AM and FM?
I am currently learning about wave modulation. In communication theory, it is said that 'rotating vector addition' generates AM (amplitude modulation) and FM (frequency modulation). What does '...
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Output levels of FM broadcast signals
I wrote an FM mono transmitter with HackRF, and now I'm trying to add stereo and RDS. I'm confused about the levels of the final mono + stereo + RDS mix (after preemphasis, and before the FM modulator)...
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I want to build an FM transmitter. How does this circuit work?
I have been tinkering with AM transmitters but now I would like to build and understand FM transmitter circuits. I came across this circuit in a electronics projects book but it does not explain at ...
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Arduino accidentally transmitting FM
I was trying to make an FM transmitter and, because I have no mic, I thought I could just use an Arduino (Uno) to generate some tones for testing. It turned out I never got a signal from the circuit ...
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Why is frequency spectrum centred at 1 kHz?
This is the circuit that I have built
I set the Continuous-Time VCO to a frequency of 1 kHz. Since there is no message signal the modulation index is =0 meaning I would expect one peak and I would ...
user279216
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What is the equivalent LTSpice diagram of the given varactor diode modulator (FM)
Given below is an example of direct FM generation using varactor diode modulator.
What is the equivalent circuit of this in LTspice?
Can you explain the given circuit?
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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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How Does Varactor AFC Work in This circuit
I have a question about how the varactor on the transistor's emitter can change the frequency of the modified Colpitts oscillator on the collector of this circuit. The junction of the varactor and R30 ...
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FM modulation in FM transmitter
I'm using an LM386 for voice amplification. The transmitter transmits the signal from the tank circuit on the correct frequency but without voice.
I'm a beginner and a hobbyist and I'm still trying to ...
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SI4735-D60 chip no FM signal reception
Trying to tune the SI4735 chip to an FM station.
Have using this library and example to drive the chip with Arduino UNO and based on the console output from the sketch the control interface works fine:...
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Is this a demodulated signal?
1st attempt
I have a problem. I built the FM demodulator circuit, but i am not sure if this signal is demodulated. This was my first attempt which following an answer, resulted in a 2nd attempt ...
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How do you find the phase lag of the current in this FM demodulation "discriminator" circuit?
I need some help understanding this discriminator circuit for FM demodulation.
(L1, C1) is the primary LC tank which resonates with the carrier frequency, whose FM signal is applied at V12. As the FM ...
