about a year ago I experimented a bit with directly generating an AM radio signal using an Arduino. Here is a short video of the working setup:
In the YouTube comments someone asked about the firmware, so here it is, attached to this posting.
The schematic is rather minimalistic:
i would love to have seen this a week ago,
how was the sound quality?
could you hear the signal on adjacent channels?(how wide is the signal)
The sound quality is mediocre, as you can imagine :) But you can listen to the received signal in the YouTube video for yourself. The signal was several MHz wide, which is also demonstrated in the video :)
i thought that may be the case, you creating the carrier with the same output as the amplitude.
with a signal that wide i bet it went away after a few meters.
i bet this could be improved with a second output and an r/c filter and transistor.
You are right about the signal strength, and of course things could be vastly improved by adding additional circuitry. But then I would rather FM modulate some carrier. However, this was just done for fun and as a proof of concept :)
this is right up my alley,
i have an dev board with an 100MHz 8051 that would work well for this. the pca can output an square wave up to 50MHz with a simple mixer and the 500K sample dac any frequency in the 10 meter band could be simulated using an linear equation in the micro.
I always wanted to learn how to do RF, but I have not been able to understand it for a year now.
This seems like an awesome idea, I never knew that you could make AM with a arduino! I thought you would require many additional passive's to get anything in the RF spectrum.
So essentially you are creating a 734 KHZ wave from the antenna? How is it several MHZ wide then?
My apologies if I am getting off topic.
My mistake. Should have written kHz :)
It should be a few kHz wide as you're mixing it with a few kHz bandwidth signal. In the limit as you're sampling at 34kHz you could have a 17kHz wide AM signal transmitted. Broadcast AM usually is only a few kHz wide and is band-limited to just over telephone quality.
Ah alright, thanks for the clarification guys! :D
Good luck with your final application of this proof of concept!