Teensy-powered AM Radio?

[suenteus]

Dear all,

I'm interested in building a low-power AM radio transmitter with a Teensy, transmitting short (<10s) audio files on a carrier wave at 200khz.

I'm wondering how best to go about this.. using the Teensy as a digital oscillator for the carrier wave and modulating the audio using a fet circuit, or even doing the modulation in software.

Can the audio library be used for this at a higher sampling rate?

Any tips would be so appreciated!

best wishes,
Jon

 

[PaulStoffregen]

Generating the 200 kHz carrier in software could be quite difficult. You'd need a very high sample rate if you want to output a sine-like waveform. Even then, you'd probably need significant analog filtering to remove harmonics.

The DAC output definitely is not fast enough. It has limited analog bandwidth. NXP/Freescale gives only a worst case spec which is pretty much just audio range, through testing shows it's much faster if not driving much capacitive load. Still, getting useful results at 200 kHz could be challenging. At the very least you'd need a good amplifier which doesn't load the DAC much.

You'd probably be much better off doing the carrier generation and modulation with convention analog circuitry.