# AM modulation

Discussion in 'General Electronics Discussion' started by Yap, Apr 11, 2017.

1. ### Yap

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0
Feb 13, 2017
Hi guys, i am a newbie in electronic field. Currently I am studying on the AM modulation. However, i saw some formula which i do not know what is it ~Can someone tell me about it ?Thank you in advance~~

2. ### duke37

5,364
769
Jan 9, 2011
Tell us where you found the first equation.
The second equation is just efficiency = output/input and applies to any energy using device such as energy from sun to heat into a room via a tree. Oil energy to delivered electrical energy.

Efficiency is always less than one. The lost energy goes into heat. Check up on entropy which always increases. (I do not understand it either)

3. ### Yap

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Feb 13, 2017
Erm i got it from some website.
Can u explain to me on single sideband transmission? From my understanding, for example, a centre carrier of 1 Mhz with modulating frequency 3 kHz will cause a bandwidth of 6 kHz. By using upper side band, the frequency of signal will be in 1 MHz to 1.003Mhz, am i right? Since the carrier will be suppressed, then the signal will be transmitted out in what medium as radio wave need to be transmitted in high frequency? @duke37

4. ### duke37

5,364
769
Jan 9, 2011
@Yap

I think you have things about right. It is possible to analyse an AM signal to look at the frequency components. This is done by Fourier analysis. All the frequencies are transmitted as radio frequency just like any carrier.

If you access the radio at the secret nuclear bunker near Nantwich (UK) it is possible to see the frequencies spread out in real time as a waterfall display. Look up hackgreensdr.org.
Lower side band signals will be seen on the 160 and 80m bands and upper sideband signals on the 20m band.. The chances of hearing a signal from Malasia is a bit slim.
Morse signals are displayed as dots and dashes but there is not enough resolution to see the very close in sidebands. The presence of signals will depend on band condtions, there may be very few or the band may be full.