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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Basic AM modulator circuit?

I am having trouble finding a good resource for understanding the design of a very basic AM modulator circuit. Specifically, I am using a simulation tool which provides an AM wave, which consists ...
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Why doesn't Class C modulator operate in saturation?

The following circuit is a class C (actually class B) amplifier used in AM modulator in my previous question. According to the textbooks, the transistor is driven into saturation in this class. A ...
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134 views

Analysis of Class C AM modulator

The following schematic is a class C AM modulator without use of any transformers I've just changed the parameters in spice to get a correct modulation. however I want to find the theoretical value ...
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115 views

Antenna for broadcast AM reception on ARM Radio SDR

I'm trying to build the ARM Radio project detailed here. I routed and fabricated a PCB for the anti-alias filter and preamplifier shown on page 2 of the linked PDF, and reproduced here: ...
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65 views

Does AM Broadcast Use Sideband Modulation

Does AM broadcast radio in the United States use a sideband modulation, or are both sidebands and the carrier present in the signal? Please provide a reference.
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323 views

A question about super-heterodyne receivers

My question is about the following paragraph: The text implies that the heterodyning process is basically done to obtain a fixed frequency before amplification takes place. Here I don't understand ...
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97 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 ...
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32 views

Compressed single-sideband modulation?

I've had an idea for a new form of SSB modulation, using half-angle formulas as a basis for compressing the sideband of a SSB voice transmission. However, this idea seems so simple that I feel it must ...
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147 views

Envelope detector

I would like to have the envelope from a signal using a simple circuit composed of a diode and a low pass filter. I know : *Tam > t >> Tcarrier *The diode must be a germanium diode because of the ...
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30 views

Single Sideband LSB Demodulation

The problem is how the phase φ effects the outcome when the input(message signal) is the DSB-SC LSB. It's : message: \$m(t)=A_{m}cos(ω_{m}t)\$ carrier: \$c(t)=A_{c}cos(w_{c}t)\$ I found that the LSB ...
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89 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? ...
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1answer
98 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 ...
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982 views

Circuits for Multiplying two Analogue Signals - AM Modulation

I've recently been learning about various communication topics and modulation schemes. One of the most basic is Amplitude Modulation and DSB-SC. Both of these modulation schemes (in addition to ...
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265 views

How to calculate R and C for AM Demodulation envelope detection?

How can I calculate the value of \$R\$ and \$C\$ for an AM envelope detection circuit. Knowing that the carrier wave is \$20\mathrm{KHz}\$, \$1\mathrm{Vpp}\$ sine wave, and the message signal is a \$...
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166 views

How do diodes work in an AM band application?

I have been trying to build an AM radio for a while now and with continued failure, I am trying different avenues. I understand that Germanium diodes have a forward drop of about 0.3V; to be sure, I ...
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1answer
142 views

Effects of DC offset and loading at the input of an envelope detector (simple diode demodulator)

I am currently designing an AM radio. I am utilizing a diode demodulator (https://upload.wikimedia.org/wikipedia/commons/6/6c/Simple_envelope_detector.svg) to extract the envelope of my carrier ...
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1answer
134 views

How to calculate capacitance and resistance for this simple A.M. radio?

\$v_i\$ is the A.M. signal, \$v_o\$ is the modulation wave. How do I calculate the optimal capacitance and resistance, for a given carrier wave frequency? If there isn't necessarily an "optimal" ...
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198 views

555 AM transmitter

I looked on instructables and I found an interesting(at least for me) AM transmitter made with a 555 timer which acts as the oscillator:http://www.instructables.com/id/555-AM-Transmitter/ Is this ...
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How are the original signal and the AM signal related?

Use the TIMS “Variable DC” module to generate a 1V DC signal. Use the “Adder” module to add this DC signal to the message signal generated in task 1 (this will produce the ...
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66 views

Calculating the Power of the Upper Sideband

I solved a question in a book that goes like this: If the carrier power is 1000 watts, what is the power in the USB at 70.7% modulation? I solved it using the formula: $$ P_{USB}=\frac{m^{2} P_{C}}{...
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56 views

Amplitude modulation transmission distortion

I need to clarify a question. Let's say that in a wire I carry a current modulated in time so that it is an amplitude modulation of a sinusoidal carrier with a modulating sinusoidal wave. In frequency ...
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1answer
81 views

In Analog to Analog conversion , why we multiply instead of adding?

When we use AM i.e Amplitude Modulation , we multiply the source signal with the carrier , My Question is , why don't we add the signals ? it would be easier to modulate and demodulate I think.
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How does an AM radio filter out only the desired frequency?

I understand that electromagnetic waves in the air induce an alternating current in the antenna. I also understand how, once you filter the signal to obtain the desired frequency, you can get the ...
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116 views

What is the pinout on my K F455P 7An filter?

I have a ceramic filter that I'm using for an AM receiver, but I don't know the pins for it. The lettering on it says K F455P 7An. I know that it's a 455 kHz signal filter and I think that it has a ...
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153 views

Amplitude of an AM wave

A message signal is modulated on a carrier wave of amplitude \$50V\$ using amplitude modulation. The modulation index is given as \$50\%\$. Find the amplitude of the AM wave. I was able to calculate ...
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953 views

Determining amplitude of a 2 MHz sine wave

I'm designing a class E resonant inverter at a switching frequency of approx. 2 MHz. I need to control the inverter so as to maintain a constant current at the load. My strategy would be to put a ...
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58 views

Attenuated Lower Envelope from Colpits Oscillator

Could someone explain to me why the output of this oscillator is the way it is? With a DC input of 6V (no small signal), I get an oscillation between -2V and 7V, which was unexpected. Is this due to ...
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2k views

What is the best and simple circuit diagram for a radio receiver to receive radio waves in Citizen's Band [closed]

I am building a two way radio system using the citizen's band in India. The transmitter is using a 555 timer IC clocked at a frequency between 26.957-27.383MHz to transmit AM waves. Can you please ...
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158 views

Drawing One-sided Magnitude Spectrum of Transmitted Signal in dBW

Question The voltage waveform measured at the 50ohm antenna terminal of a 11750-kHz AM (DSB-LC) short-wave broadcasting transmitter is shown in Fig. Q3. How to draw the one-sided magnitude ...
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188 views

Why is the RC value of a demodulator near the geometric mean of the period of carrier and message signal?

The figure below is a AM demodulator. My instructor told me to chose RC so as to satisfy the following inequality Tc << RC << Tm. Where Tc is the period of the carrier wave and Tm is the ...
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87 views

Singnals, filters and power output

I have couple of questions: A square signal goes through a low pass filter and in the output of a circuit we get a sine. What happens there? Give a scheme? This is really weird, because, from what ...
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1k views

Why AM is preferred over FM in long distance communication?

In almost all long distance communication AM is preferred over FM. Do type of modulation has anything to do with this or it is just depending on transmitting frequency?
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Radio Receiver IC

I am a Junior EE student that is interested in putting together a small radio receiver project for fun and to get some general practice with design. I have found these receiver chips from Silicon Labs ...
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Problem solving super heterodyne receiver question

I have two problems which i am trying to solve but i am stuck on the half way. I have the following first question, which i am trying to solve I have solved the problem as following, ...
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698 views

Inductor specifications for AM circuits

I am working with the book "Build Your Own Transistor Radios" by Ronald Quan in which he has a lot of AM projects. I am having a hard time figuring out what I need to buy from his specifications. For ...
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What is the tiniest, low-power, and efficient am transmitter?

Here are my constraints: I need to build an am transmitter, but it has to fit in a 1 inch diameter and ~1 inch height box. Since the box is very small, I plan to use a CR2032 battery, which is also ...
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1answer
197 views

What is the modulation technique used?

I own a Tx/Rx Radio Direction-Finding (RDF) set for a sport called falconry, basically, locating & recovering a pet falcon after flight. The Tx tag is at 218.025MHz from Marshall Radio Telemetry :...
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Making an AM radio with a silicon diode

I've been working a few days on this and have still come up with nothing. I am trying to make an AM radio using a silicon diode, but all of my attempts have failed. I believe my latest attempt most ...
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building simple radio

I'd like to build a simple AM radio (so simple it will only receive a single AM channel). What is the simplest way to build a single channel AM radio that will output to an 8ohm speaker? (e.g. 1030 ...
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1answer
270 views

How to obtain the in-phase carrier for synchronous detection of an AM signal?

I am designing an AM receiver that has a carrier frequency of 2MHz with a bandwidth of 20kHz; i.e., the information signal has 10kHz bandwidth. What I've designed is basically like this: So I need ...
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163 views

AM demodulation circuit

From the receiver circuit below, which is exactly the part that demodulates the RF signal? I know, a typical circuit used for an envelope detector is composed of a resistor, a capacitor and a diode. ...
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136 views

How to receive faint AM light

I am going to be amplitude modulating a high power LED light from a peak on a mountain. I want to recieve this faint light as far as physically possible before the light fades out too much to recieve. ...
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388 views

Determining type of modulation

The circuit below is a radio transmitter circuit of a typical RC car. The circuit makes use of IC TX2 encoder. The output of IC ("SO" pin) is a series of pulses at low speed (84 Hz). This signal will ...
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347 views

How can I Amplitude Modulate this?

I recently built this circuit, and could hear a nice full quieting signal on my short-wave radio with a 7.2 megahertz crystal for the 40 meter band. What is the simplest way I could Amplitude ...
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446 views

Amplitude modulated wave weird display in oscilloscope

In my lab experiment (http://www.ele.uri.edu/courses/ele436/labs/expA2.pdf), My amplitude modulated wave is not displaying the vertical lines-the high frequency waves of carrier (as shown in ...
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439 views

Can a Digital Signal Transceiver be made using AM?

I want to make a simple wireless thermometer using TMP36. I've seen people making it using Xbee and some RF modules but I want to know if I can use a simple AM transceiver instead of specific RF ...
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375 views

Small Signal RF Amplifer Limitations

Question: I am designing the following common emitter amplifier. This is designed with a BC547B transistor. My design is as follows: Vcc = 15V, IC = 30ma, VRe = 2.5 V, VRc = 5V, VCE = 7.5V. HfE = ...
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Amplitude Modulation Circuit Components

How does one select the values of components used in Amplitude Modulation Circuit (using a Transistor common emitter amplifier circuit)? The circuit that I designed ends up giving a weird waveform ...
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179 views

The primary selection criteria for choosing FM vs. AM is dynamic range

The primary reason for selecting FM over AM is the ability of FM to support a greater dynamic range by spreading the information across a wide range of frequencies, and using more 'horizontal ...
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Final RF envelope of FM and AM are the same

https://masi.vuse.vanderbilt.edu/images/0/0b/EECE_252_Final_Project2.pdf Page 2 spectrum plots. Effective RF electromagnetic power profile is effectively the same for baseband audio content ...