Frequently asked questions about Pettersson Bat
Detectors
Question.
Pettersson
Elektronik sells various accessories such as cables, headphones and batteries. Do
I have to purchase such items from Pettersson Elektronik or can I use other
types?
Answer.
Most standard
accessories can be used with Pettersson bat detectors. As long as you follow
the recommendations given in the Operating Instructions of the bat detector,
you can equally well purchase accessories in your local electronics store.
Question.
Is
there a "High Frequency" output on the D230/240x bat detector?
Answer.
A "high
frequency" output gives the original, unaltered signal. Such an output is
used to record the high frequency sound on a device capable of recording high
frequencies (a computer with high-speed sound card or a high-speed tape
recorder). The D200 detector has a high frequency output available all the
time, while the other D2xx detectors don't. However, pushing the Comment button
will feed the original, high frequency signal from the microphone to one of the
two output channels on the D230/240x detector. So, as long as you push this
button, you have the high frequency signal available for recording.
Question.
Can I
use a monophonic tape recorder to record from my bat detector?
Answer.
The
"Tape" output of the D100/D200/D230/240x bat detector has a
two-channel (stereophonic) jack. In order to use a monophonic tape recorder,
you need a special "stereo-to-mono" cable that connects the channel
you want to record from to a mono (2-pole) plug that fits in the tape recorder.
The D940/980
uses "phono" jacks on the Tape output, hence a mono cable is all it
takes to connect it to a monophonic tape recorder.
The D500X and
D1000X have built-in recorders so there is no need to connect an external
recorder.
If you have a
stereophonic tape recorder, you should use a two-channel (stereophonic) cable.
Question.
What
are the differences between Time Expansion and Frequency Division bat
detectors?
Answer.
Time Expansion
(TE) and Frequency Division (FD) detectors are both "broadband"
detectors. This means they will make the entire ultrasonic range audible all
the time (in contrast to a Heterodyne detector, which is sensitive only to a
limited range of frequencies at each time). There are, however, several
important differences between the two types.
An FD detector
transforms the ultrasonic calls in real time, i.e. the calls are heard through
the detector at the same time they were emitted by the bat. A TE detector first
stores a portion of the ultrasonic signal in its digital memory and then
replays it at a slower speed, i.e. it is does not transform the calls in real
time. The delay depends on the actual storage time, and if this is very short
(up to around 100 msec), the replay is also made fairly quickly and the
detector gives an "almost real time" response.
Since the TE
detector actually stores the original signal (which is then stretched out in
time), the output of such a detector provides the same information as that of
the original signal. Hence, it is possible to make any type of analysis and
obtain useful and accurate results. This includes spectral analysis of all
types (e.g. spectrogram/sonagram). An FD detector counts the number of cycles
of the ultrasonic signal and generates an output cycle (pulse) for each N input
cycles, where N is often 10. This effectively divides the frequency by N.
Obviously, an FD detector is only capable of tracking one frequency (harmonic)
at each time. Usually (but not always!), this is the fundamental frequency. Consequently,
it is not possible to perform any harmonic analysis from an FD signal. To do
this, TE signals should be used.
TE detectors
have a number of other advantages over FD detectors. For instance, the former
are more sensitive and offer the user better possibilities to aurally analyze
the transformed calls.
To conclude, if
you require a broadband bat detector, a TE detector is usually the best choice.
However, if the limited storage time of the TE detector is a problem and/or you
need a real time response, an FD detector should be chosen. As an alternative
to a TE detector, direct high-speed recording of the ultrasonic calls can also
be made with the D500X and D1000X detectors. In that case there is virtually no
limit on the recording length (storage time).