Caleb Madrigal

Programming, Hacking, Math, and Art


Digital Radio Signal Generation

Recently, I was curious if I could generate a digital radio signal from scratch just using math, and use that signal to control this radio-controlled outlet that I have.

Here's the Github source:

Generating radio signals

I want to be able to generate modulated digital signals such as this one...

original radio signal

original radio signal

This is a binary signal coded with On-off keying (also known as Amplitude-shift keying).

I'm taking the long pulses to mean "1" and the short pulses to mean "0", so this signal is transmitting the digital code, "0110100010000000".

In [2]:
# Imports and boilerplate to make graphs look better
%matplotlib inline
import matplotlib.pyplot as plt
import numpy as np
import scipy
import wave
from ...

Fourier Transform Notes

The following are my notes from a talk I gave at OSCON 2013. Here is the Github source of these Jupyter/IPython notebooks:

Sound Analysis with the Fourier Transform and Python


  1. Welcome
  2. Format of talk
    • Everything is in iPython Notebook (on Github)
    • You don't need to take notes
    • Please save questions for the end
  3. Why this is interesting
    • Sound processing is big - natural human-machine interfaces (e.g. Siri)
    • Noise reduction, Compression, feature extraction (e.g. speech)
    • Understanding our universe better (Superposition, Harmonics, Sound timbre)


  • The Nature of Waves
  • The Fourier Transform
  • Fast Fourier Transform (FFT) in Python
  • Audio analysis

In [24]:
%matplotlib inline
import matplotlib.pyplot as plt
import numpy as np
import ...