ep-413 DSP – week 14

Earth, air, fire, and water

Waves that are not sound waves.

Experiments

Transmitting music with light

light: https://reactivemusic.net/?p=8487

• Laser light at 650nM
  • What wavelength goes with a color? http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html
  • Frequency of red light is 4.6 * 10e14  = 300,000,000 / .000000650 (460 THz)

Analog radio/TV transmitters

A simple Arduino AM transmitter (Morse code) https://reactivemusic.net/?p=4450 (antenna pin D8) on 1.337 MHz

Raspberry Pi-rate radio. FM stereo transmitter using R-Pi and a piece of wire: http://makezine.com/projects/make-38-cameras-and-av/raspberry-pirate-radio/ Also see: https://reactivemusic.net/?p=10186

Analog TV transmitters, using RF Modulators and Old VCR’s: https://reactivemusic.net/?p=12355

Software defined Radio (SDR)

using Max and Pd

rtl-sdr – inexpensive open source software defined radio

• information http://sdr.osmocom.org/trac/wiki/rtl-sdr
• Where to buy one: http://www.nooelec.com/store/sdr/sdr-receivers/tv28tv2-sdr-dvb-t-usb-stick-set.html#.U2BX1K1dVKk
• installation https://reactivemusic.net/?p=8360
• sub-reddit http://sl.reddit.com/r/RTLSDR/
• Max and Pd externals https://github.com/tkzic/pd-rtlsdr

Software defined radio in Max http://zerokidz.com/radio (The user guide http://zerokidz.com/radio/docs/maxsdr5.pdf and tutorials provide a basic introduction to working with radio signals in the audio domain.

Transmitting sound in water

Transmitting signals in water https://reactivemusic.net/?p=853

Internet radio streams and recordings

• Roman Mars: Numbers Stations: http://99percentinvisible.org/episode/numbers-stations/
• You are listening to: http://youarelistening.to/boston
• broadcastify: http://www.broadcastify.com/listen/feed/15433/web
• the listening post: http://www.chilton.com/scripts/radio/R8-receiver
• Very Low Frequency: http://www-pw.physics.uiowa.edu/mcgreevy/
• The noise floor: Noise Floor: Exploring the world of unintentional radio emissions by Melissa Elliott: http://www.youtube.com/watch?v=5N1C3WB8c0o
• NASA on Souncloud: https://reactivemusic.net/?p=17377

ideas

• What is the difference between sound waves and radio waves?
• What is an antenna?
• Wave propagation is frequency dependent
• Sunspots and magnetic fields http://spaceweather.com
• Extreme frequencies, negative frequencies?

The speed of sound is 340 m/s in air (1497 m/s in water)

Speed of light is 300,000,000 m/s

wavelength = velocity / frequency

“I think [radio] is just the biggest conceptual art project uninentional or otherwise that anyone ever made. it puts Christo and those other guys to shame. Its planetary”

Roman Mars “Episode 97 – Numbers Stations” from 99% Invisible

Frequencies and modes

• Macbook trackpad: Noise 5 mHz. (try holding radio near screen too)
• Macbook AC adapter: Noise 600-1400 kHz. (~1000)
• AC adapters, LED’s, Utility poles: 3.2 Khz
• Arduino transmitter: AM 1330 kHz.
• Laser light at 650nM
  • What wavelength goes with a color? http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html
  • Frequency of red light is 4.6 * 10e14  = 300,000,000 / .000000650 (460 THz)
• Wireless micorophone (Orange-brown): Wide FM 614.150 MHz. (R band)
• Cordless phone: Narrow FM 926 mHz.
• Cell phone: Digitally encrypted trunking FM 836 mHz.
• Wifi: Digitally encoded PCM 2.4 gHz.
• FM broadcast band: Wide FM 89.7 mHz (Raspberry Pi example 98.1 Mhz)
• TV audio 600 mhz/660 mhz FMW
• The sun http://www.ips.gov.au/Solar/3/4

Looking for more…

This blog has many stories about experiments waves. Try searching, for example, for: “radio” https://reactivemusic.net/?s=radio

Assignment