Excellent Electronics Heterodyne DetectorThe bat ultrasounds are best up by the microphone SPKR1 and go through two stages of addition at Q1 and Q2. Separately, a tunable (R12) distinct abundance is produced by the LM567 oscillator U1. The LM567 is a accent decoder but actuality its ascribe is ashore and its voltage controlled oscillator is acclimated as a attention oscillator. The oscillator abundance is accustomed by
f = 1/(1.1*C4*(R10 + R12))
= 1/(1.1*0.0022*10-6*(4.7 + [0-50])*103)
= [88-7.5] khz
The two signals are alloyed at Q3 to aftermath both a arresting in the audio ambit and college frequencies that are again filtered out.
The actual audio arresting undergoes a aftermost date of controlled (R13) addition with the LM386 at U2 afore actuality accessible for achievement at AUDIO OUT. The ability antecedent is a simple 9V battery, so this apparatus is absolutely portable.
