For questions relating to frequency modulation (FM). This is a scheme where a carrier is modulated by varying its frequency to carry information.
5
votes
1answer
107 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. ...
1
vote
1answer
99 views
FM Transmitter and transmission
This is an FM transmitter circuit found in Internet Link.
Before doing ,I'm simulating in multisim. Since there is no mic input,I have given sine wave generator
1).What is frequency of wave must ...
4
votes
3answers
164 views
Question about FM and PM and Angle Modulation
I am having a bit of trouble understanding how FM works mathematically. I fully understand the conceptual basics regarding how information is transfered by modulating the frequency, but what I don't ...
0
votes
1answer
74 views
relationship between modulation index and carrier-suppressed condition in fm
What is the relationship between modulation index and carrier-suppressed condition in FM.
What should the modulation index be when the carrier is suppressed in FM?
2
votes
1answer
147 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 ...
3
votes
1answer
79 views
How do I determine the proper FM transmitter strength?
I want to build an FM transmitter that will transmit (on an unused frequency) from my laptop (near my video projector) to my receiver (about 20' away on the other side of the room). Then, I thought ...
5
votes
3answers
148 views
FM Receiver's Oscillator resonating to a frequency, but its modulated?
In an FM, the frequency is modulated. So whatever reaches the receiver is not a constant frequency. This being the case, at Receiving an AM/FM Signal: "In an FM radio, the detector is different, but ...
2
votes
1answer
92 views
Building radios using RLC Meter
I'm interested in building AM and FM radios from discrete components. Has anyone ever used an RLC meter to precisely create the inductors and other elements used in these radios? I know cheaper RLC ...
2
votes
1answer
497 views
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. ...
3
votes
1answer
147 views
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 ...
3
votes
2answers
288 views
Why did my FM transmitter mysteriously die?
I made a little FM transmitter project a few months ago. I used an Arduino, a litle 4-digit serial LED display, a couple of buttons and an FM transmitter component with breakout board
I had this put ...
2
votes
0answers
120 views
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 ...
2
votes
1answer
214 views
Audio amplifier kills FM radios signal [closed]
I have a Lepai LP-2020A+ audio amplifier and a König FM Pocket Radio.
My problem is that the pocket radio works really well on its own, with the headphone plugged in, but when I connect the radio to ...
1
vote
1answer
274 views
FM bug Circuit Issue
I implemented this circuit stripboard layout but when I connected this device to phone, there is no pulse in phone reciever. Please notify me what am I doing wrong!!
And here is my implementation ...
0
votes
1answer
147 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 ...
-1
votes
2answers
1k views
How do i calculate the frequency of an fm transmitter circuit?
Below is an FM transmitter circuit I found on the web that I would like to build from scratch.
How I would calculate the carirer signal frequency so that I know where to tune my FM radio?
If I ...
0
votes
2answers
135 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 ...
1
vote
1answer
194 views
Recommendation for si4734 external clock source
The si4734/4735 FM receiver has two options for clock input, one is to use the typical crystal oscillator (a crystal + pair of capacitors to ground), attached to the DCLK+RCLK pins, the other is to ...
2
votes
3answers
396 views
Part for VHF/FM booster?
I'm needing to create a booster and the easiest schematic I've found is this: http://electronics-diy.com/500mW_FM_VHF_Transmitter_Amplifier_Booster.php however, they do not document what part they use ...
12
votes
4answers
522 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 ...
5
votes
1answer
692 views
Good ICs for receiving and decoding FM RDS
I'm interested in doing a project to read FM RDS data. Can anyone recommend good chips for both the FM receiver and RDS decoder?
For an FM receiver, I'd like to be able to control FM frequency ...
1
vote
4answers
1k views
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 ...
