Questions tagged [am]
42 questions
16
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3 answers
Why do we not use AM and FM at the same time to transmit more information?
Amplitude modulation uses the modulation of the amplitude of a carrier wave to transmit data while leaving the carrier frequency constant, and in the case of FM it's just the other way round.
Why is a modulation of the frequency in an AM signal not…
DK2AX
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11
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1 answer
Is FM modulation still more resistant to noise when given the same bandwidth as an AM signal?
FM modulated radio is much more resistant to noise and can deliver better sound quality than AM radio. But FM signals also use more bandwidth than AM signals. In general a wider bandwidth signal is more resistant to noise / can send more data than a…
JanKanis
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11
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1 answer
Why does AM have sidebands?
Why does AM have sidebands? Isn't the whole point of AM to broadcast on ONE frequency and ONLY change the amplitude?
In the picture there is only ONE frequency and the amplitude changes, so why got AM sidebands? And why can't AM work without the…
Axel H.
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6
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0 answers
Simple AM receiver with gnuradio / RTL-SDR
EDIT: I have succeeded in getting the AM receiver to work, by replacing the AM Demod block with a Complex To Mag, and a Band Pass filter (this is noted as an alternative in the AM Demod docs).
Consequently, while I've proved that most of what I did…
Toby Eggitt
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6
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2 answers
What happens when I and Q are switched?
In https://ham.stackexchange.com/a/1068/9 it's shown that one can use
$$ r = \sqrt{I^2+Q^2} $$
to decode AM signals from a direct conversion receiver. It appears that, in this particular case, I and Q are interchangeable, thus the SDR doesn't care…
Adam Davis
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5
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2 answers
How can AM radio work differently when approaching the true frequency from different directions?
I bought a very cheap world band receiver, Nedis RDWR1000GY. It has MW, SW and FM reception. MW is useless where I live (no MW stations nearby and signals don't propagate far), but I was primarily interested in the SW and FM reception. The FM…
juhist
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5
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5 answers
Simple DIY AM receiver for 25/28 MHz
I'd like to build a simple AM receiver for 25 and/or 28 MHz to receive DCF77-formatted time code. It doesn't have to be extremely sensitive or selective - the local clock oscillator will keep time while it cannot receive the time code during my rare…
oh7lzb
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4
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1 answer
Building a crystal radio with my brother. How does this circuit work?
I'll be visiting home soon after school lets out, and I want to build an AM crystal radio with my little brother. This is the design we'll use:
http://crystalradio.net/beginners/
I'll be doing my best to explain to him how this works. I understand…
BitPusher16
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4
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0 answers
Why the value of IF of AM is 455 kHz?
Why the value of intermediate frequency (IF) of amplitude modulation (AM) is 455 kHz? Why not another value?
Wei-Cheng Liu
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4
votes
6 answers
Do changing sidebands have their own sidebands?
An amplitude changing carrier wave causes sidebands to appear next to it when viewed in the frequency domain. But if those sidebands themselves also change with time (because the modulating signal is not constant), shouldn't those themselves behave…
JanKanis
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4
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1 answer
AM Radio Envelope Dectector
How do you choose the values of the capacitor and the resistor in an envelope detector circuit? In my case, the frequency range is from
20 Hz to 20,000 Hz. Also, am I correct in understanding that usually Schottky diodes are used in the circuit…
JackLalane1
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3
votes
1 answer
feasibility of wireless passive crystal earphones
I just learnt about such a thing as a crystal radio receiver and the following idea came to my mind. I have no background knowledge on electronics nor anything related.
What if battery-less earbuds can be made, picking AM waves from very short range…
user2464424
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3
votes
1 answer
Why are FM radio waves less susceptible to interference than AM?
When studying modulation of radio waves (or of most electromagnetic waves for that matter) I came across this question:
Why are FM waves less susceptible to interference than AM waves?
I know that in FM the frequency has been modulated to carry the…
MystMan
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3
votes
6 answers
Would it be feasible to set up a SSB or AM 2 meter repeater?
Would it be feasible to set up a SSB or AM 2 meter repeater? I want to set up an AllStar full duplex node and like the idea of AM because stations can double without issues. SSB works for weaker signals and it takes up less bandwidth. The circuitry…
Skyler 440
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3
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1 answer
I/Q demodulation of DSBSC-AM signals
I was looking at some Stereo FM demodulators on the Internet, and I can't understand
the use of the complex to real block for demodulation of the L-R signal (DSBSC-AM)
which can be seen in different projects, for…
Ardavast Dayleryan
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