Make: Radio

185Experiment 11: Metal Detector

mixer, as shown in Figure

11-7

. It compares

the two oscillator signals and generates an

audible signal if the frequencies differ.

Figure

11-8

shows how the mixed output

depends on the frequencies of the two

oscillators as they go in and out of phase

with each other. When they are exactly or

almost in phase, the mix has a generally

low output. When they are exactly or almost

out of phase, the mix has a generally high

output. The variation between a low output

and a high output happens so quickly, it

creates its own audible frequency.

The idea of comparing two signals to

generate a new signal at their difference ...