User's Manual

Lotek Biotracker Receiver User’s Manual Page 11
Antenna input
The connector is a standard BNC ‘bayonet’ socket with an impedance of 50 ohms.
Headphones Socket
This is a 3.5mm stereo jack socket designed for a matching stereo jack plug. The
headphones supplied with the receiver have 32 ohm speakers. These are standard
personal stereo headphones. Headphones with 8 ohms speakers can also be used,
though they increase the power consumption. A mono jack plug can be used, but the
sound will be quieter.
The internal speaker cuts out when headphones are used. However, we can supply a
special adapter lead, if you would prefer the speaker to continue to sound.
The battery will last longer when headphones are used instead of the internal speaker,
and weaker signals can be heard using headphones. Therefore we recommend the use
of headphones whenever possible.
If required, a special lead with an ‘in-line’ volume control can be supplied to enable
volume to be controlled independently of receiver gain. This is mainly to enable signal
loudness to be adjusted without affecting the signal strength indicator. It is not
necessary to use this lead to get the best performance from the receiver. However, for
tracking very powerful tags at close range it may be useful to further reduce signal level.
Please note that it is not necessary for the gain to be on maximum to get the best
receiver sensitivity (i.e. to hear the weakest signals). When using headphones, set the
gain to a level which is comfortable, not on maximum. Receiver sensitivity starts to
reduce below a gain level of about 60; above this there is no advantage other than to
overcome extraneous noise (e.g. when not using headphones).
Serial Port (RS232)
The serial port enables receiver gain, frequency and channel to be controlled by a
computer via a serial connection. The receiver is wired for a straight-through cable to
the PC (no cross-over of Tx and Rx lines). The use of the serial link is explained later in
this manual. USB adaptors are available for computers with no serial port.
The wiring is shown below (9-way ‘D’ connector, viewed from outside the box)
Pin No. Function
1 Not used
2 Tx
3 Rx
4 Not used
5 Ground
6 – 9 Not used
The serial data protocol is as follows:
1200 baud
1 start bit
8 data bits
1 stop bit
no parity checking
no handshaking
1
2
6
3
7
4
8
5
9