Questions tagged [am]
Amplitude Modulation (AM) modulates a signal by varying the amplitude of the carrier. The ease with which it can be demodulated made AM radio broadcasting popular before FM demodulation was cost effective.
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How does an emitter follower work as an AM detector?
Can someone explain how an emitter follower used as an AM detector (shown below) actually works?
I don't get how a (theoretically) linear system like an emitter follower would work as a detector when ...
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Solving an exercise of superheterodyne receiver with high IF frequency
I've been struggling with this problem for several hours. I have a high IF superheterodyne receiver. The input frequency can vary from 9kHz to 3GHz. I need to calculate the minimum intermediate ...
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How can I only let a specific frequency pass in an AM receiver?
I wanted to create an AM receiver and I know partly how to demodulate the signal. I know I need to use a low pass filter to get the low frequency audio signal, but I don't know how to only get data ...
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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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Where and how are the carrier and message signal multiplied in this circuit?
I have this circuit diagram of an AM modulator and I am trying to understand what is going on.
I know that the c(t) is taken from the collector of transistor Q1 and the multiplication of signals : m(t)...
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Yet another 807 tube transmitter
I just can't seem to get away from these 807s. Although I am to the point where I might replace them with 6146s.
I built this transmitter with a 6AG7 oscillator, and 2x 807 final amplifier. The ...
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FET AM modulator
I have been meddling with a FET-based AM modulator. I implemented a basic circuit as attached here along with its output. Is the output as it should be? If not, what am I doing wrong, and how can I ...
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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 is this resistor important in my AM radio transmitter?
I've been building an AM radio transmitter and had a few questions about my diagram. I built this using components on a breadboard. Having the resistor there is critical otherwise it doesn't work. The ...
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Diode AM detector linearity
Most valve radios use a vacuum tube diode as a detector. Over the decades, I have used germanium diodes with good apparent performance. In other words, cheap equipment sounds good when the germanium ...
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What is the function of these transformers in an AM transmitter (Sender 5000 solid state AM transmitter)?
What could be the function of these transformers in the back of the Sender 5000 solid state AM transmitter?
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PCB8711 Rev. A of Sender 5000 solid-state AM transmitter: schematic symbol
I wonder what the symbol encircled below means, because we're repairing an AM transmitter.
I think the real-life version of that schematic looks like this:
I really wonder what the symbol encircled ...
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Trying to make a quadrature amplitude modulation - Having problems in the quadrature output
Here is the transmitter circuit:
This is the receiver circuit:
I think everything is fine in the AM transmitter but not in the receiver circuit.
In the 'in phase' part of the receiver circuit, I ...
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Trying to recover signal in AM modulation
The circuit above is the AM transmitter and the other circuit is the AM receiver. The AM transmitter consists of: Baseband signal (source), BB amplifier and adder (MixerIn), mixer (it's a pulse/square ...
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How to buffer an AM signal?
The above shows an AM modulator circuit which sums a sine wave and a triangle wave to produce an output which will undergo resonance using RLC to produce an AM signal.
The TL072 is commonly used in AM ...
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How does one test an AM antenna matching network?
I'm lost. I need to test two AM matching networks. I was not given training and I'm a newborn compared to every other guy in AM Radio out there.
I do own a osciloscope with Bode plot generator but I ...
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AM demodulation circuit doesn't work
I'm designing AM modulation and demodulation circuits. The AM modulation works fine but when I connected it to the demodulator (I'm using envelope detection) the modulating signal changed to the ...
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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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Mechanical buzzer heard on AM radio
If I connect this little mechanical buzzer to a 3V supply, then hold my AM radio close to it with the radio tuned so I can't hear any stations, I can hear the buzzer on the radio. If I turn up the ...
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Is AM radio louder the closer you are to the transmitter?
Following on from this question, does the volume of the receiver increase the closer it is to the transmitter because it's receiving more of the radio signal? This question specifically is for a ...
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Why is the voltage the same before and after the diode in LTspice?
In LTspice, I setup a circuit with a voltage generator giving a 160 kHz signal AM modulated with a 440 Hz signal and I'm trying to amplify this signal with a differential op amp.
Why is the voltage ...
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Simple analog AM radio generating noise throughout circuit [closed]
I'm building a simple AM radio circuit for one of my classes. It works insofar as that anywhere from 400 Hz - 4 kHz we get a nice AM radioey tone. But when the outputs are connected to an oscilloscope,...
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My AM radio receiver using TA7642 IC is not working
A very simple question I’m sure, but I’m struggling with making an AM radio using an TA7642 AM radio IC.
I’ve looped maybe 200 coils of 0.25 mm enameled copper wire around a 1 cm ferrite rod and made ...
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Request for circuit review: varactor-tuned AM radio receiver
I apologize if this is not the place for newbie questions or circuit review requests, but I was hoping for some wisdom on an AM receiver circuit I have sketched out.
From left to right it is intended ...
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Tuning problem for an AM radio receiver
After some months I went back to try to make my AM radio work.
This is the schematic:
ANT is a 16 meters long straight copper wire (insulated).
R1 and C2 gives a time costant \$ \tau = 114 \, \mu s\$ ...
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How to switch an AC signal
I have two AC signals, and I want to control their flow (either allow them to pass or open the circuit), therefore, I can imagine that the solution to my problem could be the same for both of these ...
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Envelope detector followed by a low pass filter
What are the advantages of adding an RC low pass filter after an envelope detector? I am asking this because I often notice (in multiple studies) that this type of circuit logic (in the figure below) ...
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why do i have to add a capacitor to observe AM output
so our TA asked us to simulate this modulator in lTspice but told us to add a capacitor that has a value of 0.1 uF at the output and record the result and confirm the envelope shape from message ...
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Find min and max of magnitude ltspice
I am doing a amplitude modulator simulation in ltspice, I am trying to find the minimum and maximum amplitude of the modulated signal using .meas, I found some ...
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Measure current of 51 kHz signal and ideas for increasing range of AM signal
I have built the following circuit:
I got it from http://www.discovercircuits.com/PDF-FILES/PIPEFINDER1.pdf
It works Ok and generates around 520 kHz in the wire, but I have some questions.
I measured ...
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How to calculate C for an AM demodulator?
I have read this equation from Savant's book that is used to calculate the capacitor for a demodulator:
I've tried to calculate my circuit with this equation, but it didn't work. Then I tried to ...
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Amplitude Modulation
Hello, I'm new to this topic as it is my school works, I try to simulate the diagram below by using Proteus which I follow accordingly with the labsheet given from my school.
The problem is the ...
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How to implement "burst" functionality for bare-bones function generator
Some fancy function generators have a burst feature which gives precise control over on-time and periodicity of the desired waveform.
Ex: For my application, I have a 25 MHz sin wave (2.5 Vpp) and, in ...
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What does it mean for a "baseband" signal to be a signal near zero frequency range?
I'm trying to understand the intuition and math of "baseband." Wiki says it is a signal near zero frequency range. Don't all signals of any type need a frequency otherwise they are not a ...
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Troubleshoot DIY AM radio
I need help troubleshooting my DIY radio. I am following the schematic this link.
See pictures below for a diagram of how the components are wired and the actual wiring. The design I made is different ...
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Amplitude modulation with JFET
I have found a circuit that does AM modulation with a JFET transistor (2N5485). I modified it slightly and ended up with the circuit below. A sample output is also given.
I used Microcap 12 for the ...
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PWM/PPM with external carrier
I want to generate PWM/PPM signal with external supplied carrier e.g. for 'outphasing' AM transmitter (for educational purposes). Convetional methods of PWM generation implies that carier signal has ...
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Watt output of radio station
I was wondering how many watts an AM radio station outputs, and if I can calculate the watts on a tuned antenna by this equation:
Where Win = the watts input for the antenna, Wout = the watts output ...
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AM modulator's negative peak saturation issue
I am working on AM modulator. I am using NMOS as a voltage controlled resistance, and opamp in inverting aplifier configuration to get carrier signal multiplied by input signal.
I created a simulation ...
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Hearing only noise and ticking sound with simple AM radio - The art of electronics
I've tried to build the simple AM radio that is proposed at page 56-The Art of Electronics (3rd).
The idea is to tune my radio on a frequency of 657 kHz (I'm sure there's a station at that frequency)....
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Do AM radio broadcasters pick frequencies that are picked up as interference on purpose? [closed]
This is not meant to be a political question, rather a historical one, USA based.
Every place I have lived, if I have an amplifier with a long enough input wire, I will start picking up AM radio if I ...
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Envelope detector RC values [closed]
I have understood how the envelope detector works, but I am unable to find the formula for R and C appropriate values. The closest I have found is this link:
Explain The Square Law Demodulation and ...
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Use opamp for demodulation and amplification
For small frequencies (20-20000Hz) the opamp has output more than -3dB
If we make a low frequency AM receiver , can we use an opamp for demodulation instead of a diode and for amplifications instead ...
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SIMULINK: The spectrum of the modulated signal remains unchanged despite modification of the modulation index
I try to implement a frequency modulator.
From what I know, the more I vary the modulation index (which is set by the gain block here,) the more the spectral lines should increase in number.
When I ...
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Does satellite radio use AM or FM or both? [closed]
Somehow, I cannot find an answer anywhere... I am guessing both...
Several actual satellites had FM in their names, so perhaps that is a clue, but I want to know for sure...
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AM radio antenna optimization
I am an RF noob and am trying to understand if optimizing an AM crystal radio antenna (maximizing the signal transmission from the antenna to the LC tank) is practical, or even makes sense. Here is a ...
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Ring modulator with matlab [duplicate]
I'm a bit newbie in DSP. I'm trying to modulate two signals and create DSB-SC am signal. I choose ring modulator for it. So can anyone show me any working ring modulator circuit?
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Gaussian signal generation circuit
I was studying op amp application and saw the square wave, triangular wave, sine wave. I was wondering if it is possible to generate Gaussian shape wave with op amp. I am basically trying to modulate ...
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AM circuit LTspice
I have to analyze the following circuit and understand its function.
As far as I understand the top part is the simple phase-shift oscillator generating output sine wave at circa 145kHz.
The NE555 is ...
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