Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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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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)?
Ian Rehwinkel
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AM Modulator Mixer Circuit

I found a very basic AM transmitter circuit on the youtube video here. The schematic is below: I'm a bit confused on the op-amp circuit on the right. It seems that the op-amp is really only taking the difference between the message and carrier…
superkittens
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Why is superheterodyning better than direct conversion?

What is the advantage of having the extra stage of IF, extra local oscillator and extra filtering stage and amplification. It just seems like more work and circuitry. Surely the direct conversion to baseband and the intermediate conversion to…
Lewis Kelsey
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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 envelope of the signal and drive a speaker. What I…
Rag
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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 AM) My current thinking is along the following…
Jon
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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 detection effectively involves converting an AC…
kene02
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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). C1 is a variable capacitor between 20 to 55…
SirLeoncavallo
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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 Modulate this signal with a microphone or computer…
skyler
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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 crystal/diode based AM receiver. I would expect most…
horta
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Tube transmitter tuning

I am trying to tune/tweak/repair this transmitter for a friend of mine. It is oscillating, and it has rf power on the antenna, but it just doesn't seem as "strong" as it should be. The diagram says 35-40 watt carrier. Now its a class A final amp,…
McMurdo
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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 frequency to 5 kHz. But FM signals require a…
GNZ
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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 must be a reason why in literature the longer EM…
user16307
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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 low frequency signal (NF) and the high frequency…
DK2AX
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Making a suitable antenna for a crystal radio

I'm trying to build a simple AM crystal radio, however, I'm not getting any voltage registered when using it. This is the kind that's only powered by the radio waves. The site I was using to design it makes the circuit clear and how the radio works…
RadioSchmadio
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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, and listen to only one at a time, or is there…
Doubt
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