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Topic: Turn your Arduino into an AM radio transmitter! (Read 31254 times) previous topic - next topic

echogecko

Thanks for this thread - this is a really fun project starter.

I've been hoping to do some proper amplitude modulation of the carrier, but it seems as though whatever the carrier level is set to once the code is flashed is a constant value (on or off), rather than one that can be varying with the modulating signal.   

So I was wondering...is it possible to vary our carrier  (if the project is set up as in the original post) to achieve proper amplitude modulation? 

Would varying the carrier by an arbitrary amplitude envelope ( e.g a song from an mp3 player or smartphone) result in successful modulation for radio transmission?  And if so, how many ways are there to do that with a basic arduino kit?


Sorry if these seem like daft questions -  I normally work with AM/FM signals in the audio domain, not radio.   

GoForSmoke

Get a DAC module or buy a Due or similar (has stereo DAC outputs) and get proper analog out.
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

dirkroos

As a licensed radio ham I found this interesting and immediately built it.
And trying to find a quick and easy way to slightly tune it I tried setting the OCR1A value from 1 to 0.1 and was stunned with the result.

1. The frequency remained on 8khz
2. Output power increased by 18db  WOW!

(tested on proper rig and results are repeatable)

Interesting

Could someone explain

GoForSmoke

You set an 8 bit register to a 32 bit float what could possibly happen?
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

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