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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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Amplitude modulation with diode

I was studying about amplitude modulation and I found this circuit on the internet. Does anyone know why that ground is needed? Is the first part(three resistors) an adding circuit? Does the diode ...
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1answer
82 views

How to increase range of AM radio waves? [closed]

As a personal project, I made a very simple AM transmitter with an idea from an online tutorial, using a 1 MHz crystal oscillator (plus power source, antenna, breadboard, etc.). However, when using ...
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1answer
71 views

RC transmitter and receiver for Raspberry Pi possible? [closed]

I've got a pet project in which I'm trying to write/build a self learning autopilot for my rc plane. I've got a Raspberry Pi with an IMU and a pitot tube in the plane and it can now control the servos ...
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4answers
110 views

What happens if the frequency of the receiver osc does not match (exactly) the carrier frequency?

I thinking about FM and AM. Theoretically the carrier frequency is perfectly match the demodulation frequency. But what happens if there is a mismatch? I think using AM the frequency of the base-band ...
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2answers
892 views

Why are the resistors in an AM modulator necessary?

In preparation for the amateur radio exam, I have been following the preparation course material by DJ4UF. In the section about modulation it presents this diagram of a simplified AM modulator. The ...
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3answers
10k views

Are audio cassettes FM or AM?

I know that cassettes store an analog signal, but is the signal Amplitude-Modulated (AM) or Frequency Modulated (FM)?
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1answer
76 views

How is the signal Multiplied with the Carrier in AM

In wireless transmission, via Amplitude modulation, we multiply the message signal by a carrier wave to get the modulated signal $$x(t) = m(t) \times cos(\omega t)$$ Where \$m(t)\$ is the original ...
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1answer
76 views

Stereo Enhanced Mono

Medium Wave AM in most countries is monophonic. AM stereo was never universally adopted. Given a monophonic signal, how can one create a stereo output? I know there are some 'tricks' you can play on ...
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49 views

AM question, sketch AM signal and envelope

I was wondering if i was doing this problem correctly. I ask because when I have looked for answers, they have all differed online and mine itself is different than that as well. Dont bother with the ...
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4answers
144 views

Signal Theory paradox

Very often we apply to circuits sinusoidal or constant voltages, and we study methods (like the phasors method) to analyze them. Here's a simple question to which, in many years, I have found not yet ...
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3answers
101 views

Multi-tuning AM selector

I'm thinking about the design of an AM receiver frontend that needs to select between three channels. The community suggested that I investigate manually wound loop antennas, and they seem like a nice ...
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1answer
64 views

Multi-fixed-station AM receiver

I'm in the pencil-and-paper stage of building a radio receiver that has the following characteristics: AM shortwave/HF three fixed frequencies - 3.33, 7.85 and 14.67 MHz single upper sideband with ...
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1answer
31 views

Pearmability Tuning Vs Cap tuning for MW AM

I constructed a wide band Hi Fi TRF tuner for MW AM that sounds great. It used an old 365 pF air spaced 3 gang variable capacitor that had equal sections. Selectivity was marginal at the top of the ...
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1answer
1k views

How can I modify the frequency of a simple 433mhz transmitter module?

How can I change the frequency of a simple RF transmitter? These are the transmitters in question: Background Research On this question s3c says: To change ...
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1answer
55 views

Is possible to modulate the upper and lower sides of a carrier with two distict signals?

I would like to modulate in amplitude the upper and lower sides of a carrier with two distinct signals. Would it be possible? There is a specific name for this scheme of modulation? The detection ...
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1answer
63 views

AM radio Attenuation.

I have built the following AM radio circuit : I was able to pick several radio stations. I fixed the variable capacitor so that I can only hear the 1230 kHz station which I identified from the FCC ...
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2answers
145 views

How to create an OOK signal in ADS

I'm trying to make an OOK modulated signal in ADS. I need a random bit generator, and a block to multiply a sinusoidal signal with that random pulse. I did this in Cadence by the 'rand_bit_stream' and ...
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3answers
1k views

Full AM signal vs DSB-SC

I conducted an experiment where I constructed a Full AM signal and changed the message signals amplitude to change the modulation index of the Full AM signal. I then increased the amplitude of the ...
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1answer
167 views

Germanium Diode 455KHz AM Detector

Ge Diodes have been used for AM detection many decades before Si Diodes became cheap.They were attractive when compared to the large power hungry valve .Nowdays Si diodes are much cheaper and easier ...
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2answers
92 views

Flatness vs Frequency parameter in RF zero bias detectors

I require the measurement of RF power from a port, and I am considering using a zero-bias RF detector in order the measure the power being delivered through the port. These devices give a voltage ...
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1answer
343 views

Understanding a simple crystal oscillator transmitter

I try to understand the AM transmitter on the figure below, but I cannot figure out two essential things. The carrier frequency is created by the crystal oscillator chip. Why does it suffice to put ...
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1answer
2k views

Why do FM radio signals occupy greater bandwidth than AM?

If a 5kHz baseband signal is modulating an AM carrier wave, the sidebands will be centered around the carrier wave and the the signal will occupy 10kHz bandwidth. AM radio limits the upper modulating ...
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2answers
850 views

Demodulate a AM signal from the carrier using Matlab

So the AM signal has a bandwidth of 5kHz and the carrier signal is 100kHz. I demodulate the AM signal by multiplying it to a sin function (sin(2000000*pi), same frequency with the carrier frequency). ...
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2answers
216 views

Can AM and FM signals at the same frequency be separated?

Suppose one radio station emits an amplitude modulated (AM) signal at 100 MHz, and a nearby station emits a frequency modulated (FM) signal at 100 MHz. Is it possible to separate these two signals, ...
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2answers
626 views

Can I make this AM Transmitter circuit a longer range?

Our teacher want to make us a long range AM Transmitter. I try to search it on the internet and I found one simple AM Transmitter circuit in YouTube channel Afrotechmods. But I try this and not ...
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1answer
238 views

What does “a 40 kHz wave modulate with a 1 kHz sound” mean? [closed]

what is mean when say "a 40 kHz wave modulate with a 1 kHz sound"? which of AM or FM Modulation means?
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1answer
41 views

Radio Noise from Storm

I drove through a Wyoming thunderstorm today. Just for fun, I set my AM car radio to the top end of the AM broadcast band where there was no station audible. Sure enough, I heard the lightning ...
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2answers
1k views

AM modulation bandpass filter?

I'm trying to do an AM modulation using band pass filter at the output the carrier is at 600 kHz and the message signal is at 1.5 kHz. To get a 100% modulation I did some calculations to get fL=598.5 ...
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1answer
377 views

AM Detector Peak Vs Average

The Envelope detector is over 100 years old .In its classic form it is a simple half wave diode that peak detects the carrier with the load resister and load capacitor time constant chosen to allow ...
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1answer
81 views

AM modulation circuit modification

I have an assignment on AM modulation. I implemented a circuit and the output wasn't exactly correct, the output is not symmetrical about the x-axis. I'll post screenshots which might explain the ...
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1answer
133 views

How to amplify the envelope of a signal at envelope demodulator?

I have a wave with ~ <10% modulation. Is there any way to amplify the envelope of a signal at the envelope demodulator end? You can barely make out the envelope in the image below but I think I ...
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1answer
224 views

Amplitude demodulation on receiver receiving higher frequency than initial message tone [closed]

I'm using an envelope detector to demodulate my AM signal with the schematic below. I'm expecting to hear a 1Khz tone at V_demod but when I listen in on the signal, the frequency of V_demod in real ...
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1answer
240 views

20 Mhz AM transmitter and receiver - Receiver does not receive [closed]

I am doing a circuit for an AM transmitter and receiver. I extracted it from http://www.pyroelectro.com/projects/pyro_rf_receiver_27mhz/index.html. Receiver: I have already done the transmitter, ...
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1answer
478 views

AM (Amplitude Modulation) Colpitts

How would I amplitude modulate the Colpitts oscillator directly? Can this be done by making Vcc the audio signal and DC offsetting the audio signal in order to get the Colpitts to fundamentally ...
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3answers
243 views

AM radio Transmitter with one station DIY - microcontroller

I have to build a project with a AM transmitter and receiver. The idea is that I will speak something which will be transmitted and received to the receiver. The Transmitter and the receiver assembly ...
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126 views

Fundamentally utility of sidebands FM

In my course of telecommunication they're talking about Frequency Modulation with the mathematical working-out of the Bessel-graph, but it's not clear enough to understand the goal. First we've looked ...
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3answers
1k views

Modulation scheme for simple signal generator

As part of a vintage radio restoration project, I decided to build a simple signal generator for alignment. The idea was straightforward, a short distance AM transmitter with a variable carrier ...
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1answer
635 views

How can a foxhole radio tune in on a frequency without a capacitor?

A primitive foxhole radio only consists of an antenna, coil, diode and headphones. There doesn't seem to be an LC-resonator, so how does this radio tune in on a carrier frequency?
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2answers
144 views

what is wideband phase shifter in modulator?

in these days I have been studying communication systems. and I want to know the role of wideband phase shifter in the picture above.
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4answers
393 views

Why there is no resistor in an AM Detector?

Consider the simple AM detector below: Inductor L1 and capacitor C1 builds the "tank circuit", which purpose is to filter all frequencies, except the selecteded one. However, I'm having trouble to ...
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1answer
548 views

AM Demodulation with Envelope Detector

I have to project an AM demodulator using an Envelope Demodulator. To which kinds of AM (DSB, DSB-SC, VSB, SSD) is it applicable to? Thanks
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1answer
448 views

A 50 kW carrier is to be modulated to a level of 85%. What is the carrier power after modulation?

I'm getting answer as 36.73KW but in the book its given as 50KW. My calculation : P(total) = P(carrier)(1+(m^2)/2) 50 = Pc(1+.85*.85/2) Pc = 36.73KW. What am i doing wrong here?
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1answer
758 views

Power of AM signal [closed]

I need to calculate the power of the sidebands and the carrier. The carrier is 10*cos(2pi10⁶t) [V] and the modulating is 3*cos(2pi10³t) [V]. The modulated signal is 10*cos(\$w_0\$t)+\$\frac{3}{2}\$*...
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2answers
304 views

Why won't my JFET Hartley oscillate

I built this Hartley oscillator (taken from the November 1990 edition of Popular Electronics) as part of an AM modulated signal generator project. But, it steadfastly refused to oscillate. I was ...
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3answers
2k views

What role does the capacitor play in an AM demodulating circuit? [closed]

The goal of this question. Demodulate the AM signal. (Please assume a diode demodulating AM radio of the most imaginable simplicity.) I am assuming an alternating current sine wave is coming into ...
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1answer
353 views

How does this transistor radio mixer work?

I recently picked up a transistor radio, a Unitra Nova 206. I've been studying the schematic with an interest in the AM operation for now. Most of it makes sense and I've included an annotated ...
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0answers
64 views

Ge Vs Si for AM envelope detector

Early solid state radios used Ge diodes as a detector .Si was not available then so this makes sense .Impedances were much lower than the Valve stuff.A 5k Log volume control pot was common for early ...
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3answers
292 views

Why does this common-source MOSFET amplifier work?

I have built the MOSFET amplitude modulator shown in the bottom right onto another class C oscillator tube circuit, and it does work. I am having trouble understanding why based on what Ive read. ...
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3answers
71 views

AM Radio gets static when driving near PV arrays, but not FM

My school has PV arrays that act as shades in the parking lot. Whenever I'm within 10ft of them, I get overpowering, humming AM static, but the FM signal is clear as day. Why?
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6answers
492 views

Can we transmit FM signal using AM band and AM signal using FM band?

What I am asking is if it is possible to transmit a frequency modulated wave in AM range(550-1650 Khz) and similarly to transmit an Amplitude modulated wave in FM band (88-108 Mhz). I would like to ...