Amplitude modulation tutorial & AM radio transmitter circuit

This video covers the history of the discovery of radio waves, to the creation of simple oscillator based radio transmitters. Then I explain what modulation and amplitude modulation are, and show you how to build a low powered AM radio transmitter.

Original design by Stefan0719:
http://www.youtube.com/watch?v=f42W9jNHMZ0

Kickass music by imeddy
http://www.youtube.com/watch?v=MzptQ4ZuTTI

Category:

Science & Technology

Tags:

• AM
• amplitude
• modulation
• radio
• transmitter
• circuit
• tutorial
• electronics
• RF
• electromagnetic
• frequency

[gemis94]

Are the source signal and modulation output around 90 degrees out of phase at 5:22? I mean shouldn't the amplitude of modulated signal be 0 when amplitude of source is?

[Afrotechmods]

@gemis94 The phase should be the same.

[MrJonagikster]

Is it viable to use a BJT amplifier instead of an OPAMP? Are they able to amplify at sufficient frequency?

[Afrotechmods]

@MrJonagikster Of course

[oo131193oo]

Is it maybe possible to use a 741 op amp? does it really not work?

[Afrotechmods]

@oo131193oo Not a chance. The 741 is an old POS from the 70s and can barely do anything useful above 100kHz.

[Afrotechmods]

@busybjorn There are dozens of modulation schemes, all with their pros and cons. AM is very susceptible to noise (ever notice how AM always sounds crappy in your car?) whereas frequency modulation is much less affected by noise. An AM receiver is very easy and cheap to build, but an FM receiver is a little more challenging. Overall for broadcasting voice and music short distances, FM is by far the better choice.

[Celiecinema1]

How about frequency modulation? Could you do a video on frequency modulation?

[Mrkirill578]

Great video! Is there going to be a video about LC filters in the near further?

[paliwp1]

Hello Afrotechmods, the second amplifier which is shown at 5 min and 35 seconds is powered exactly same as the first amplifier? Thank you for your time.

[0sakar0]

simplest and understanding video ever at youtube. lots of Thanks, you did a great job

[MisterAlexUk]

Thank you.

[uniqueandprosperous]

is there a way to key on & off 7.?? to 10.?? times per second whole number down to 2nd decimal & send that through a 144 klhz carrier wave ??

[FoulplayMFer]

would fap again

[bas12345654321]

@Afrotechmods

I just made a Colpitts Oscillator, that works too.

Just with a BC546, works fine for my.

[FelixTheHouseFreak]

So glad you mentioned and gave credit to Nikola Tesla

[ivan3x]

duke nukem 3D !!! :) thanks for the clean instruction and tutorial :) Please go on with more complicated subjects like PID with opAmps. opAmps are my favorites. please more videos :)