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.

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Building an fm transmitter broadcasting simultaneously to all fm frequencies [closed]

I would like to build an FM transmitter that transmits a signal to all fm frequencies simultaneously, so that any nearby radio tuned to any frequency can receive this signal. Is it possible to do this ...
1k views

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 ...
187 views

Bessel Differential Equation and Angle Modulation

I'm trying to undestand the role of the Bessel differential equation in calculating the side bands of a phase modulated signal. I started out with the textbook example u_{PM} = cos(w_C \cdot t + \...
1k views

Improve output quality of FM receiver TEA5767

I have connected a TEA5767 to my Arduino board using I2C and can tune it fine (see instructable.com). As antenna a ~70cm long simple cable is connected. I've connected a cheap 5V amplifier. ...
243 views

Questions about FM Mic Kit Schematic

I'm currently building an FM Microphone kit and I'd like to understand its operation before physically putting it together. The documentation only provides an overview of some aspects and provides no ...
939 views

How do PPM FM channels work? [closed]

I know the difference between AM and FM. What I don't get clearly is how the transmitter with a single antenna can transmit up to nine different channels with almost no interference between channels. ...
70 views

Calculated result for inductance seems wrong?

I'm building an FM radio transmitter kit which includes an LC tank, where C is a tuner capacitor of ~30pF and the resonant frequency is ~100Mhz. The value of the PCB trace inductor, however, is not ...
1k 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 ...
756 views

Is there anyother way to construct an FM transmitter

I recently built an FM transmitter that uses a combination of coil and capacitor as an oscillator to generate the carrier frequency. I built this transmitter: Now my problem is that I find it ...
2k views

Is it illegal to transmit in the FM range for personal use

I am building an FM transmitter. It is going to be designed to transmit only for a short range of around 50 to 100 meters. My question is whether it is illegal to transmit signals in the FM band over ...
707 views

Can an inductor be substituted for a coil

I am designing this FM receiver circuit. I have a few questions related to the circuit. Buying coil in my locality is a little expensive. So would it be alright to substitute an inductor in its ...
230 views

College Computer/Electrical Engineering Circuits - Modulating Signal DC offset based of modulating index question

Here is an image of the question. I am stuck at part a, which asks to find the DC Offset based of a modulating index of 0.7, or 70%. So essentially, you will transform the maximum and minimum, yes? ...
291 views

Found a part on an old FM transmitter used for tuning. What is it?

This is an old transmitter from the early nineties. The part is the white block with the screw through it. I'm assuming it's a capacitor of some sort, but other than that I don't know much. I don't ...
483 views

Fm reciever 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 ...
140 views

Describing FM inductors

Why, when providing FM radio designs, do people use physical parameters instead of electrical? I.E. 2 turns, 20awg, 2cm dia.
141 views

Hint for the way a fm reciever works

As far as I know , a simple AM reciever 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 ...
178 views

What's the next logical step in applying input to this FM transmitter circuit?

Last year, I posted this question about a very simple RF transmitter circuit: Does this simple RF transmitter circuit actually work? I built it myself, and actually remade it after I posted an answer ...
467 views

How to send analog data using FM/FM Telemetry

I am measuring the strain a bicyclist is placing on a bicycle crank arm throughout riding, using strain gages. I would like to send this data (after amplification) off of the bicycle crank arm and to ...
2k views

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 ...
2k views

FM Carrier Wave Generation

I'm trying to understand how the following FM radio schematic works. Specifically, I want to know how the carrier wave is generated. I understand the concept of an LC tank and I think I see it ...
6k views

If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

If an FM signal has different frequencies according to the modulation, how does the radio receive the signal in a fixed frequency like 103.2 MHz?
1k views

Can we send text data over FM radio? [closed]

Can we able to broadcast text data over the FM radio.If yes, how can I implement this.
4k views

USB to 3v converter to power a battery powered FM transmitter?

I have a SCOSCHE FM Transmitter which practically eats up 2xAAA batteries, I was thinking of using my TV's USB power for the transmitter. My search lead me to this 3 in 1 DC-DC USB 5V to 3.3V Step-...
1k views

What is this type of radio fm antenna connector called?

I'm looking for an antenna replacement for my dad's busted radio (iHome IH8) and I'm having some trouble finding the name of this type of plug. The only things I find when searching online are coaxial ...
215 views

Objections to use an RCA connector for antenna in broadcast FM receiver

Due to budget & space restrictions, I am thinking about replacing a PCB BNC connector used to attach an external FM antenna. It seems to me an RCA connector could be an option, given its good ...
175 views

Triangulation with Single Tone FM TX and Three RX using Phase Detection [closed]

I'm looking for some IC and frequency suggestions to accomplish the following task. Modulate a tone onto a carrier and continuously broadcast this signal toward an array of three receiving antennas(...
1k views

Video Home System (VHS) bandwidth

Standard play VHS video cassette recorders offered only about 3 MHz luminance bandwidth by recording the signal on an FM carrier. What is that carrier frequency? Is it possible to confirm the carrier ...
350 views

what is the function of pre-emphasizer and dee-emphasizer in Stereophonic FM Receiver?

what is the purpose of theses two block ? I know that pre-emphasizer will boost the high frequencies before transmission and dee-emphasizer will reducing them by a corresponding amount in the ...
171 views

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 ...
118 views

FM Antenna Question

I am a swim coach trying to play music for my swimmers while they swim. I am currently using this transmitter with this antenna . I have no issues with the transmitter as it is more than powerful ...
3k 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 ...
1k views

Use Preformed inductor instead of coil for FM Transmitter

I want to build this transmitter: The inductor in the schematic says 0.1uh so I figured I could get some of these and use them instead of making my own like it describes in the picture. I would be ...
1k views

555 timer as FM transmitter vs. Tank Circuit

This site seems to suggest the use of the 555 timer in astable mode to generate frequency modulation from a source. The typical transmitter uses a tank circuit with an inductor and trimmer capacitor ...
7k 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 ...
292 views

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 ...
1k views

Frequency spacing and the doppler effect

Suppose that I'm working on a system which needs to use a transceiver with an FM signal. If that system moves very fast (i.e. it is a satellite or whatever) in which the maximum doppler effect can be ...
5k 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 ...
129 views

FM signal example

Sorry if this question is too basic, but I'm a software engineer student who must study communication systems. I try to represent a FM signal in a graphing calculator, but I don't know why the result ...
172 views

FM receiver used to control a switch

I am new to this and I would like to ask for advice on FM receivers. I want to create a very low powered (mass produced) item that has a super bright LED, battery and then related circuitry(for FM). ...
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 ...
57 views

Range of FM and Power

Why is the range of an FM signal shorter than AM signal? I thought it was due to the high frequency of FM signal getting absorbed by physical barriers. Is it so? Does power of a signal has any role to ...
892 views

I have a test tommorrow on phase lock loops, AM/FM receivers along with several other topics. I need to understand this topic clearly before I take the exam to advance to the next schooling in the ...
469 views

Why feedback is needed in PLL FM Demodulator?

I am trying to build FM Demodulator in FPGA. The architecture I am trying to use is PLL-based FM Demodulator like the one below. I searched for the working principle of this demodulator but there is ...
4k 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....
7k views

How to make a RF Choke?

I am a high school student and am making a project on FM receiver for class 11. I am following this circuit diagram: The L2 in this diagram is a 22µH RF Choke. The part listed in the website has the ...
81 views

I want to listen TV channels without display (terrestrial) just like FM Radio channels. There are lots of FM receiver circuits on the web but I couldn't find for TV channels. Is such a thing possbile ...
315 views

There is a missing component in this circuit and couldn't figure out why?

I'm designing a BA1404 Stereo FM transmitter and I found the following source: Source Link You can find the component list, circuit scheme and the other stuff on this page. But when I look at the ...
825 views

simple question regarding frequency modulation (FM)

I have a question on frequency modulation. For example, the following signal is frequency modulated: y(n)=sin(2*pi*(400+cos(2*pi*4*t))*t). Since the maximum of cos function is from -1 to 1, so I ...
327 views

Will BA1404 circuit work with TEA5591A

For an electronics project I would like to build stereo FM transmitter and receiver circuits. I was just wondering if these two circuits would work together. The BA1404 circuit can be found here. ...
940 views

FM and phase/frequency deviation

I have a small understanding issue here, so I would be very glad if someone could help me a bit! We are given this FM modulated signal to volts; ...