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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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)...
Ardavast Dayleryan's user avatar
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Ratio detector FM demodulator

The aim of the exercise is to design a ratio detector FM demodulator circuit. UPDATE: I changed the circuit: This is my transient analysis in output: I found the information about AC analysis and ...
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Uniden BC780XLT Radio scanner, unknown modification

I recently purchased an old Uniden BC780XLT scanner. It has been modified replacing two smd resistor with THT resistors with different values. I am curious about this modification: what does it do? I ...
Wolfdale's user avatar
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High SNR FM demodulation

So I need to demodulate the FM signal from a sensor with highest SNR possible, at least 70-75 dB. IF is 10.7 MHz, max. deviation is 200 kHz but I can change those values if needed. Baseband signal ...
cyrtex's user avatar
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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 ...
Zearia's user avatar
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Is it possible to make a Raspberry Pi transmit FM on several frequencies at the same time?

I have read a few questions here on transmitting on multiple frequencies at the same time. But all of them was about transmitting the same signal to all frequencies. The PiFM and PiTX projects are ...
Christian Wattengård's user avatar
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121 views

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 ...
Daniel's user avatar
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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 ...
Jorge Aldo's user avatar
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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 ...
KE Keronei's user avatar
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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 ...
Dj Obsidian's user avatar
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instataneous frequency in FM

Newbie and trying to understand the concept of instantaneous frequency in FM. Basic equation is \$A\cos(2\pi f_\mathrm{c}t+ 2\pi k\int (\mathrm{message})\,\mathrm{d}t)\$. I wanted to know how the term ...
vishnu's user avatar
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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 ...
Bali Vinayak's user avatar
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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 ...
Zearia's user avatar
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Superheterodyne receiver with voltage controlled oscillator

I'm new in electronics and I want to create a FM receiver that performs a product of the received RF signal and a local signal (the local signal is also frequency modulated with a Voltage Controlled ...
Mehdi asselman's user avatar
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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 ...
user207421's user avatar
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Frequency modulation occurs not in an expected way

I've built this oscillator. Then I gave it a DC bias and connected an mp3 player. Result: I have local fm-stations muted at 90MHz, 90.75MHz and 89.25MHz. However, at 90MHz an mp3 music is very ...
ivan's user avatar
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Good compact antenna for FM audio transmitter module?

I've been looking at building a short range FM transmitter using this module, the idea is to create a small module that I can integrate into other projects. I'd prefer having the antenna on the same ...
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Why is it difficult to write the close loop transfer function of a frequency modulated DC-DC converter (for eg - LLC converter)?

I know how to derive and write the transfer function of duty cycle/pulse width modulated DC-DC converter. We need to linearize the switches and then write KVL/KCL equations and then derive the output ...
Sudhanva Gokhale's user avatar
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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 ...
user305532's user avatar
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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 ...
Grag's user avatar
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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 ...
Ferrofluid's user avatar
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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 ...
digiwizkid's user avatar
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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 ...
Userhanu's user avatar
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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 ...
Hamed's user avatar
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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 ...
apoch's user avatar
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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:...
axk's user avatar
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Bessel function of frequency modulation and modulating index

If the amplitude of a message signal is kept fixed, and the frequency is increased, then will the modulating index decrease? According to thr Bessel function the side tones will be more spaced when ...
soumyadip_poddar's user avatar
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FM antenna isolation

I want to connect a car antenna (FM radio) to a phone's jack sleeve to provide a good antenna signal to the phone (for its FM radio part). As the car might add some supply DC to the antenna, I decided ...
Daniel's user avatar
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How to check for frequencies with stronger signal in FM radio

I'm making a radio player using si4703 IC. I read RDS data to know the radio station name, PI code, etc. I also get the list of alternative frequencies (AF) that the radio station send via RDS. ...
naggety's user avatar
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Fm receiver circuit doubt

I was trying to simulate an FM receiver circuit on LTSpice. The circuit is given on this website I want to know how the correct current/voltage will look around the speaker (modelled as 8-ohm ...
A Q's user avatar
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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 ...
Mark37's user avatar
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Connecting an FM radio receiver circuit to a speaker via 3.5 mm audio jack?

As an experiment and for educational purposes, I wanted to build and connect an FM receiver to some old computer speakers via a 3.5 mm audio jack. So I tried building a circuit like this on a bread ...
learningtech's user avatar
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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 ...
GeekWithGlasses's user avatar
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Make Si4703 evaluation board Bluetooth capable

While looking for a Bluetooth RDS-TMC receiver which could be queried with FOSS software, and after realizing there’s probably not too much on the market, I stumbled across Si4703 evaluation boards ...
user149408's user avatar
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1 answer
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Noise floor of a FM duplex

If these 2 signals, that form this duplex, have ranges of 15-30 [kHz] and 30-45 [kHz] using: \$NoiseFloor_{dBm} =10\log _{10}(k\times T_{0}\times 1000)+NF+10\log _{10}(BW)\$ and if \$K,T,F\$ and \$\...
rkcepelin's user avatar
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For which purpose are those resistors on the ANT output?

I've bought a cheap FM transmitter and installed it in my car, but sadly, it gives me too much interference (Too weak signal), even in a totally static signal, so I decided to disassemble the ...
Fusseldieb's user avatar
-1 votes
1 answer
61 views

Frequency demodulation circuit

This is how I designed the frequency modulation circuit, but I cannot perform the demodulation process. It can be done with a PLL but I couldn't install it. How can I demodulate?
Orhunemre's user avatar
-1 votes
2 answers
12k views

How to remove the static sound in an fm transmitter

Hi I have a school project and I used the schematics from this website for our FM transmitter. Its actually working but its hard to recognize the music being played because of the static, also does ...
Miguel Lorenzo's user avatar