QTech Data Systems DATRAN Q80 Telemetry Radio User Manual

Page 16

TECHNICAL NOTES

www.qtech.co.nz

Tel 03 3663713

Circuit details of Radio Interface.

The opto isolators OPT1 and OPT2 provide isolation of the Maxon radio transmit key and busy lines between the
Q80 module and associated equipment.

Tra

Transmitter Key

nsmitter Key

The Maxon radio transmitter is keyed ON by pulling the TXKEY line to ground. The transmitter keyed KY LED3 will
turn ON. The TXKEY line ON current is approximately 10mA.

Receive Busy

The Maxon radio busy output line switches opto isolator OPT2 ON via transistors Q4 and Q5 when the radio
receiver is busy. The busy/mute MU LED2 will turn ON. The busy output line BUSY will sink current to ground via
the opto isolator output transistor. The BUSY output line can sink a maximum of 10mA.

Transmitter Audio Level

Potentiometer VR2 is used to set the Maxon radio transmit audio level. The required level is –3dBm for +/- 3kHz
(+/1.8 kHz) transmitter deviation.

Note

Set +/- 3 kHz deviation for 25 kHz channel spacing and +/- 1.8 kHz for 12.5 kHz channel spacing i.e.
narrow band channel. These are the required levels when the Q80 Module is to be used with

QTech

RTU

modules.

Receiv

Receiver Audio level

er Audio level

Potentiometer VR1 is used to set the received audio level. The required audio level is +/- 3kHz (1800Hz) deviation
of Maxon radio received signal produces –15dBm audio output.

Note

Set +/- 3 kHz deviation for 25 kHz channel spacing and +/- 1.8 kHz for 12.5 kHz channel spacing i.e.
narrow band channel. These are the required levels when the Q80 Module is to be used with

QTech

RTU

modules.

Audio Level Adjustment

The transmit and receive audio levels are preset by

QTech

prior to delivery and should not normally require

adjustment.

Note

The 600 ohm modem line terminating resistor in the

QTech

RTU modules should be removed, i.e. not

installed.

To set the transmit and receive audio levels proceed as follows: