Title: Simple AM Radio Signal Generation
Post by: Markus Gritsch on October 03, 2011, 01:13:23 pm
Post by: Markus Gritsch on October 03, 2011, 01:13:23 pm
Hi,
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:
http://www.youtube.com/watch?v=y1EKyQrFJ-o (http://www.youtube.com/watch?v=y1EKyQrFJ-o)
In the YouTube comments someone asked about the firmware, so here it is, attached to this posting.
The schematic is rather minimalistic:
[attachment=2]
Have fun,
Markus
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:
http://www.youtube.com/watch?v=y1EKyQrFJ-o (http://www.youtube.com/watch?v=y1EKyQrFJ-o)
In the YouTube comments someone asked about the firmware, so here it is, attached to this posting.
The schematic is rather minimalistic:
[attachment=2]
Have fun,
Markus
Title: Re: Simple AM Radio Signal Generation
Post by: sqkybeaver on October 03, 2011, 04:43:39 pm
Post by: sqkybeaver on October 03, 2011, 04:43:39 pm
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)
how was the sound quality?
could you hear the signal on adjacent channels?(how wide is the signal)
Title: Re: Simple AM Radio Signal Generation
Post by: Markus Gritsch on October 03, 2011, 04:49:19 pm
Post by: Markus Gritsch on October 03, 2011, 04:49:19 pm
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 :)
Title: Re: Simple AM Radio Signal Generation
Post by: sqkybeaver on October 03, 2011, 04:54:07 pm
Post by: sqkybeaver on October 03, 2011, 04:54:07 pm
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.
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.
Title: Re: Simple AM Radio Signal Generation
Post by: Markus Gritsch on October 03, 2011, 04:59:20 pm
Post by: Markus Gritsch on October 03, 2011, 04:59:20 pm
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 :)
Title: Re: Simple AM Radio Signal Generation
Post by: sqkybeaver on October 03, 2011, 05:11:00 pm
Post by: sqkybeaver on October 03, 2011, 05:11:00 pm
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 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.
Title: Re: Simple AM Radio Signal Generation
Post by: hak8or on October 05, 2011, 05:19:14 pm
Post by: hak8or on October 05, 2011, 05:19:14 pm
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.
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.
Title: Re: Simple AM Radio Signal Generation
Post by: Markus Gritsch on October 05, 2011, 05:32:09 pm
Post by: Markus Gritsch on October 05, 2011, 05:32:09 pm
My mistake. Should have written kHz :)
Title: Re: Simple AM Radio Signal Generation
Post by: AdShea on October 05, 2011, 10:29:35 pm
Post by: AdShea on October 05, 2011, 10:29:35 pm
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.
Title: Re: Simple AM Radio Signal Generation
Post by: hak8or on October 06, 2011, 12:12:43 am
Post by: hak8or on October 06, 2011, 12:12:43 am
Ah alright, thanks for the clarification guys! :D
Good luck with your final application of this proof of concept!
Good luck with your final application of this proof of concept!