Project XTAL Radio
Building a radio? In biology? How can that be?
We all love our electronic toys, radios, stereos, CD players, MP3 players, computers, DVD players, short wave
radios, amateur radio, TV’s, X-boxes, Play stations, VCR’s, cassette tape players, 8 track tape players, reel-to-
reel tape players, and record players. All these devices require electricity by either plugging the device into an
electrical outlet or by inserting batteries.
The radio you are about to build is an environmentally friendly radio. This radio is built from recycled parts. It
does not require batteries and it is not plugged into an electrical outlet. This radio will play forever for free!
How? It obtains all of its power from the transmitted radio wave.
Think about this, for as long as there are AM stations transmitting in the AM broadcast frequency range, this
radio will work. That could be 10, or 100 or more years from now. Be as creative as you want building this
radio, build it as neat or as unique as possible, keep it, and pass it off to your offspring, grand-offspring, or great
grand offspring. It is possible that this low-tech radio could outlive all of those electronic devices mentioned
above … and it will still work for free!
Xtal
is the radio abbreviation for crystal. These radios are called crystal (xtal) radios because the original radios
used a crystalline mineral for the detector. The most popular mineral used is galena, followed by pyrite. Modern
crystal radios often use manufactured devices called diodes. Careful examination of a diode will reveal a tiny
hair-like structure coming in contact with a tiny crystal of germanium (see following pictures).
My classroom objectives - Biology (Ecology unit):
1. Build an environmentally friendly radio using
only
recycled components.
2. Develop a commentary on two issues about how this is an environmentally friendly radio.
Cross Curriculum Objectives:
1. English – Use concrete evidence to formulate a commentary about how this radio could tie in with the
crisis in the book Alas, Babylon.
2. Mathematics - Mathematical formulas are derived to calculate the amount of wire required to wind the
coil and the surface area of the capacitors. Use mathematical equations to determine the inductance,
capacitance and approximate frequency coverage of the radio.
