Mike wanted to uniquely identify plants growing in the rows of a field and looked for ways to do that. One way is to measure electrical resistance between stalk base and leaf and thereby uniquely identifying the samples. This proven not to work as there was no way to distinguish measurements taken on the same plant from measurements taken between plants. So he think another way, to measure AC impedance. This technique has actually proven much more interesting. Doing some experiments he found that plants can act as decent antennae. To find out, he decided to build a simple AM radio transmitter. The AM transmitter is build around a ATMega324 8-bit AVR microcontroller and uses embedded timer/counter modules to produce the carrier wave. Check details of this interesting experiment on the link below.
Simple AVR AM Radio Transmitter - [Link]