Ciel EaM Batz 2.0, Manual

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General information about your detector:
The heterodyne detector (HD):
A heterodyne detector works similar to a broadcast receiver. The
frequency you have chosen will be subtracted from the bat call with a
bandwidth of +/- 5 kHz transforming it to the audible range.
As an example : Detector is set to 42 kHz
Call frequency Setting Difference Effect
48 kHz 6 kHz not/barely hearable
47 kHz 5 kHz hearable
46 kHz 4 kHz hearable
45 kHz 3 kHz hearable
44 kHz 2 kHz hearable
43 kHz 1 kHz hearable
42 kHz 42 kHz 0 kHz not hearable
41 kHz 1 kHz hearable
40 kHz 2 kHz hearable
39 kHz 3 kHz hearable
38 kHz 4 kHz hearable
37 kHz 5 kHz hearable
36 kHz 6 kHz not/barely hearable
You can use the HD detector like a radio and search the whole ultrasonic
range for bats. A bat call has a wider range than one frequency, so you
will be able to hear it across the whole 10 kHz window of the detector.
When turning the thumbwheel you can now hear the frequency and the
volume changing. Try find the best and loudest playback of the call. The
display then shows the peak frequency of the call.
Ultrasonic sources which emit single frequency sine or square wave signals
will be heard on the detector as a beeping signal. If the frequency of the
detector is similar to the frequency of the source there will be no audible
signal at all. This is because you are subtracting the detector frequency
from the source signal with the result of 0 kHz. If you now tune up or
down you will hear a rising beep.
Heterodyne detectors are used for manual data collection. It is the easiest
way to identify species in the field depending on the quality of the call and
the shown frequency. It is very difficult or even impossible to gain results
as precise as these by using FD or TE detectors in the field. If you want to
analyse a recorded heterodyne signal you have to know the original call
frequency. The benefit of analysing software is very limited with HD
recordings.