3 ms·
First realize the aptitude modulation in this radio is very crude. Unlike normal radio which has many amplitudes, this radio only has 2. On and off. Tone or no
by randyrand 9y ago
First realize the aptitude modulation in this radio is very crude. Unlike normal radio which has many amplitudes, this radio only has 2. On and off. Tone or no tone. This radio has no control over the exact amplitude.
Due to this limitation, this radio can only transfer a single tone at a time. Music must be monophonic.
To transfer a 60htz tone we just switch between the on and off state at 60htz. The On state will be at some random amplitude that we can't control.
What are these states? In the On state, we write to a memory address repeatedly very very fast (as fast as the computer allows). And in the off state we sleep.
- lovelearning 9y agoAh ok! So far, I was trying to unsuccessfully fit my mental model of normal amplitude modulation to what this code is doing. Your two statements "This radio has no control over the exact amplitude. On state will be at some random amplitude that we can't control" were exactly the missing gaps I needed to clear my confusion. Very well explained, thank you very much!
- anfractuosity 9y agoDespite the fact you can only modulate the carrier on/off, you can still also output normal music with speech etc using pulse density modulation - https://news.ycombinator.com/item?id=16168317 https://news.ycombinator.com/item?id=16168317 Which I don't think is monophonic, but I could be wrong?
- randyrand 9y agoHow does a pulse density modulated audio signal sound to the human ear? You may be right if that you tube clip is any indication. Neat!