Last night's DIY

[The Dong]

James R. Coplin wrote:
> Last night I built a bat detector and sat outside with my son and a cocktail
> listening to the bats overhead. Based on a simple circuit found here:

You'd probably detect more than just bats, like certain insects and the 
neighbours television whine. We have a lot of bats that feed just 
outside the back window near a light.

I don't know about everyone else, but I can hear bats quite clearly. 
Maybe most and especially the larger species of bats have a significant 
part of their sonar squeaks reach into easy hearing range.

> About $20 in parts.

You must have built the boutique version ;)