Eight Innovation EBD2766 Eight Build Complete Construction Kit to Create Your Own Fully Functioning Bat Detector, One Size, for 14 and Above, 1 pieces

Product Information

Broadband bat detectors can simultaneously detect all frequencies and also offer the facility to make sound recordings for identification and further analysis. Broadband detectors include frequency division detectors, time expansion detectors and full spectrum detectors. Of these, the full spectrum bat detectors are undoubtedly the best bat detectors on the market combining the detailed call structure capture of the time expansion detector with the real time continuous monitoring of the frequency division detector. Unlike other bat detectors, the full spectrum detector also records in the original call frequency, whilst still allowing you to listen to the incoming converted frequencies in real time. FSC’s ‘A Guide to British Bats’ is a fold out, laminated guide to help you identify bats through physical appearance and call frequency.

So just how accurate are the identifications given by this bat detector kit? The short answer is you get an accurate ID about 80% of the time. But the more complete answer is that it depends on two factors: the species and the Auto ID Sensitivity setting you use during recording.This is done with a simple binary counter. I used the CD4040 which is somewhat overkill as it can divide in steps of 2 up to 4096 and I chose the output that divides the input signal by 16. Only 4 stages of 12 of the binary counters are used. I have tried this unit directly against a much more expensive heterodyne frequency selectable unit (my partner uses these for professional bat surveys) and I could hear virtually no difference in the output sounds. In fact I would have said this kit was more sensitive. The main benifit of the professional unit is the frequency range selection, which aids with species selection. Another issue with this kit which uses an ultrasonic receiver is the sensitivity range of the receiver, which has a peak around 40kHz, but again it works well over a very wide range of input signals as the analog signal is converted into a digital pulse train. Please note: While not difficult to make, this kit does require quite a lot of soldering. It is recommended for people who have already done a bit of soldering and will take in the region of 1-4 hours to solder. When I build it I decided to use the dividing method of detection. With that methode you amplify the sounds of the bats so much that it is clipped. It transforms from a sinewave to a squarewave. This squarewave still has the frequency that the bats use.

There is no way to tune the frequency with a pot. This is a pretty simple frequency divider (rather than a more complex heterdyne). Basically for every 8 pulses put into the device only 1 will appear at the output. Hence the ultrasonic pulses (in the region of 40-80kHz) will be stepped down to 5-10kHz and hence we can hear them. Wildlife Acoustics is a big name in the world of wildlife audio research and they’ve built some of the most advanced wildlife sound identification software available. One of Wildlife Acoustics software products is called Kaleidoscope Pro Bat Auto ID. They’ve developed classifiers for 38 bat species in North America, which covers almost every species you’re likely to hear. But they’re also constantly adding to their list of classifiers for other regions of the world. At the time of writing they created classifiers for 37 species in the UK & Europe, 37 Neotropical species, and 21 in South Africa. You can see a complete list of species here.

Instructions

Let’s use North America as an example. Based on the most recent Classifier Performance Table we can see that using the “ Sensitive” setting you’ll receive an accurate ID about 70% of the time on average. However, some species tend to get confused more easily, while others have more distinct echolocation calls. You’ll get an accurate ID about 97% of the time if it’s a Spotted Bat ( Euderma maculatum) and only 31% of the time if it’s a Cave Myotis ( Myotis velifer).