Because Ken requested it, here's a simpler example for FM broadcast. Just alternating between a tone and silence. Perfect for creating your own secret russian military station.
Also interesting is the effect the system clock has on the signal quality (easier to notice on complete silence): It being particularly high isn't that important, but some frequencies have a lot more noise than others. It probably depends on the harmonic relationship to the channel frequency.
Comments
Because Ken requested it, here's a simpler example for FM broadcast. Just alternating between a tone and silence. Perfect for creating your own secret russian military station.
Also interesting is the effect the system clock has on the signal quality (easier to notice on complete silence): It being particularly high isn't that important, but some frequencies have a lot more noise than others. It probably depends on the harmonic relationship to the channel frequency.
Thanks for posting the barebones radio transmission program! I've used it here to compare P2's spectral purity with that of the P1.
-Phil
Here's what the spectrum looks like for the FM transmitter with modulation completely suppressed:
The peaks are at 88, 231, and 408 MHz (i.e. not harmonically related).
This is for the chroma technique. The spectrum for the DDS technique is virtually identical.
-Phil
They are image frequencies.
320-88=232
320+88=408
640-88=552
640+88=728
Ah, indeed they are. Thanks for noticing that.
-Phil