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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How can this FM transmitter modulate?

simulate this circuit – Schematic created using CircuitLab This is a minimalist FM transmitter I've found from http://www.talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-1.html I'm ...
Parth Parikh's user avatar
2 votes
1 answer
2k views

Single-station FM radio

I'd like to build an FM radio that is pre-tuned to a specific station. I could use something like the Si4703 FM tuner chip, but they're expensive and difficult to solder by hand (and require a ...
JeffThompson's user avatar
3 votes
1 answer
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Simple FM transmitter [duplicate]

How does this circuit perform Frequency modulation. I know the LC generates the carrier frequency. How does the transistor act as a varicap to perform FM. Which part of the circuit acts as a varicap ...
emperor_penguin's user avatar
6 votes
1 answer
5k views

Variable Capacitor?

I am working on a simple FM radio transmitter and I was looking for a variable capacitor to help tune the circuit. I rummaged around and took apart an old Sony radio that had this component in it. ...
masoug's user avatar
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3 answers
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simplest FM radio receiver?

As per this building simple radio it is the simplest AM radio receiver. obviously this is very poor AM receiver.(but it was working for someone in comment) I'm wondering what will happen when this ...
koolwithk's user avatar
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4 votes
3 answers
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FM transmitter design?

I stumbled across a relatively simple FM radio transmitter online. Credit: makezine.com I wanted to understand how it works (it is called "super simple" on the website), but several hours I have ...
user2514631's user avatar
1 vote
4 answers
514 views

FM Transmitter oscillation problem

I've been trying to get this simple FM transmitter to work over the past few days and I could use some help in a few areas. First iteration was on a breadboard with all parts included. The ...
Ciphergeek's user avatar
1 vote
1 answer
2k views

How is FM modulation is achieved using a single BJT

I want to understand how this circuit achieve frequency modulation. The BJT is a 2N3904. I found that millers effect comes into play and varies the frequency of the tank circuit about a center ...
Sakibul Alam's user avatar
1 vote
3 answers
2k 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 ...
Bali Vinayak's user avatar
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0 answers
84 views

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
15 votes
4 answers
3k views

Receive several fm-radio stations at the same time (~10-20 MHz wide summary at 90MHz radiofrequency)

What is a cheap way to receive and record on PC several (tens) of fm-radios (public, e.g. news, music, etc)? Such radios uses frequencies like 90.4 MHz or 102.7 MHz, sends a stereo (sometimes with ...
osgx's user avatar
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7 votes
2 answers
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Why do EM waves with longer wavelengths propagate longer distances?

AM radio signals use carrier waves which are quite longer than in FM case. We know that in free space both high and low freq. RF signals should take the same distance in same period of time. There ...
user16307's user avatar
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6 votes
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Capacitor between emitter and collector

Considering the circuit below.: What is the purpose of capacitor C5? I know it provides positive feedback to sustain the LC oscillations, but how does this work ?
emperor_penguin's user avatar
5 votes
3 answers
1k views

FM Quadrature detector - is it the best choice

My input is an FM carrier of 80.00MHz. It is FM modulated with 625kbpsec data. The deviation from carrier is about +/-700kHz. The data never spends more than about 38us in a low state or high state i....
Andy aka's user avatar
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5 votes
1 answer
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FM Transmitter Modulation

I am designing an FM transmitter as a learning experience and for fun, but I am having some difficulty with FM modulation. I am using a VCO with a Colpitts topology and common emitter configuration. ...
Ag565's user avatar
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4 votes
4 answers
7k views

Does this simple RF transmitter circuit actually work?

I've come across this circuit a few times while searching for simple transmitter circuits, and decided to try it. According to this site, it should be transmitting at around 90Mhz. http://www....
Ten Bitcomb's user avatar
3 votes
1 answer
5k views

How to build an FM transmitter and how does it work?

I have become interested in radio transmission and would like to know how to build an FM radio transmitter. When I search for information I either get a block diagram or a video of someone putting it ...
ngatesh's user avatar
  • 51
2 votes
1 answer
2k views

Understanding this simple FM receiver

I know the theory of FM, but I just can't understand how this simple circuit works. So let's say a radio station is transmitted on 100 MHz, as I understand in this case the oscillator should also ...
Isty001's user avatar
  • 25
2 votes
4 answers
8k views

Using a Dipole Antenna on a 50 ohm FM transmitter

First of all, while I'm not new to electronics, I'm new to the radio world. I am helping a friend overseas set up a community radio, and am getting everything set up over here before I ship it. I ...
Nimaid's user avatar
  • 161
1 vote
2 answers
2k views

How does this simple FM slope detector work?

I understand what happens from the diode onwards, it's a rectifying amp and a low pass filter that filters any unwanted frequencies from the carrier, but what is going on in terms of voltage between ...
A Federico Osuna Hdez's user avatar
1 vote
1 answer
6k views

FM Radio transmitter and receiver circuits

I'm planning on building a FM transmitter and receiver circuit for an electronics project. I was just wondering if these two circuits would work together. Also would they be suitable for transmitting ...
Darth Vader's user avatar
1 vote
1 answer
8k views

Whats the principle of a PLL used as demodulator of a FM signal?

I didnt quite understand te following: A basic PLL consists of the following parts: phase detector low pass filter VCO If you input a 1MHz sine the PLL will try to lock on it by controlling the VCO....
Barry's user avatar
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1 vote
1 answer
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Detection of FM transmitter carrier phase

I would like to detect the phase (only) of a standard FM transmitter carrier over the air while it is modulated, while at the same time avoiding receiver threshold effect. Typical commercial FM ...
Palapaguy's user avatar
0 votes
1 answer
484 views

Voltage Controlled-Phase Shifting Circuits

Forewarned: I have a somewhat good understanding of signals and systems but electrical engineering circuits aren't my strength. Question: Is there a simple circuit that can introduce a voltage-...
Jordan McBain's user avatar
0 votes
3 answers
7k views

Send text data using FM frequencies [closed]

I want to design a device which receives basic text wirelessly, and outputs this text on a display. Using Wi-Fi is not a option. I have an idea that it would be possible to do this using FM ...
Smeestad's user avatar
0 votes
1 answer
320 views

Building a telephone spy

I am implementing the following circuit but I am stuck at one point. How can we input the wires in IN1 , IN2, OUT1, OUT2? I don't know which wire to insert because there are almost 4 or 5 wires ...
Umer Farooq's user avatar
0 votes
2 answers
291 views

Limit a radio to a single station

We are organizing a game for students where we are transmitting the daily objectives and hints over from an FM transmitter. Is there a way to limit basic radios to only be able to pick up a certain ...
JamieHoward's user avatar
0 votes
1 answer
5k views

Use Potentiometer to change frequency in FM Radio Transmitter

I know that in most circuits you use a tank circuit consisting of an inductor and variable capacitor in parallel to generate different frequencies like this one. However since most cheap trimmer caps ...
NULL's user avatar
  • 213
0 votes
1 answer
994 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 ...
Archimedes's user avatar
0 votes
2 answers
4k views

Simple FM Radio Receiver project

I've been making my own simple FM radio. I know it's not quite appropriate to make this stuff on breadboard, but if it works, I'll move in on the board and solder it. I wanted to ask why my radio is ...
MerryGR's user avatar
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1 answer
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FM Transmitter Circuit (range 3 km) on Multisim

I am new to the telecom simulations system specially multisim, which I am having a project that I want to simulate. My project in (Analog Communications) is consisting to have FM Transmitter (...
B Happy's user avatar
0 votes
2 answers
922 views

Need help understanding simple FM transmitter

I made a simple FM transmitter following https://maker.pro/custom/tutorial/how-to-make-an-fm-transmitter and it worked! Now I need some help to understand how. My coil is made of 1 mm copper wire has ...
Andy's user avatar
  • 265
0 votes
4 answers
818 views

Different antenna lengths for different frequencies?

I just want to understand a few things which I couldn't get clarity from a lot of websites searched through google as I could see differing information. My questions : How does a single FM antenna ...
user avatar
-3 votes
2 answers
3k 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 ...
user151005's user avatar