q-Tech Q71B User manual
Q71B –1200 bps FSK Radio Modem
for DATRAN XL4 Plus, XL4 & eXcel RTUs
Quick Start Guide
Q71B –Quick Start Guide –v1.4 –May 2022
www.qtech.co.nz Ph: +64 3 366 3713 Page 2 of 6
Overview
The Q71B modem allows you to connect a DATRAN RTU via an RS232 serial port to a DATRAN 1200bps
radio communications system using the V.23 FSK protocol but without the backward channel. This allows
1200bps in both directions as the modem uses a special turn around feature.
The Q71B interfaces to either a Tait TM91xx/TM81xx radio fitted with an internal Q82 interface, or a
DATRAN Q80 telemetry radio.
The radio type needs to be specified at time of ordering so QTech can supply the correct interface cable.
Each Q71B is supplied complete with a 1m Radio cable and a 300mm RS232 serial cable (RJ45-RJ45).
Part number Description
PD9310-Q82 Q71B modem for Tait TM91xx/TM81xx radios - 300mm RS232 cable and 1m radio cable.
PD9310-Q80 Q71B modem for DATRAN Q80 radios - 300mm RS232 cable and 1m radio cable
PD9310 Q71B modem, no interface cables
The Q71B can also be used for the DATRAN base station radio for systems using the Tait TM91xx/TM81xx.
Please order part number PD9310-Base.
The base modem has different internal jumper settings and is supplied with a plug pack power supply and a
RJ45 to DB9 Female serial cable part number CAB-Q71-PC.
Prerequisites
If using the DATRAN XL4 Plus or XL4 RTU, all firmware versions are compatible.
All versions of Workbench software are compatible.
The DATRAN II eXcel RTU must have Q03 firmware v5.21 or later.
The Q90 software required is v3.27 or later.
Q71B –Quick Start Guide –v1.4 –May 2022
www.qtech.co.nz Ph: +64 3 366 3713 Page 3 of 6
Power Supply Connections
The Q71B is designed to operate from a nominal 12V DC supply voltage within the range 8.0 to 15.0V DC.
A supply voltage greater than 15.0V will blow the 500mA fuse inside the Q71B.
A supply voltage less than 8.0V will result in degraded or unreliable performance.
The DATRAN XL4 Plus, XL4 and eXcel (Rev D) RTUs have two RS232 ports - both can use the Q71B for
analogue radio communications.
The significant difference between the two ports, is that the lower RS232 port (RS232-B) on the Q22D has a
+Vsup DC output supply line. The Q71B can be powered via this line, so long as jumper J23 on the Q22D is
in the 1-2 position. RS232-A port on the processor board does not have this supply line, so the Q71B must
be powered through the three terminal power supply connector. The power supply connections are shown on
the top cover
Left Pin
Middle Pin
Right Pin
GND Power Supply Negative
+12V Power Supply Positive (8V –15V DC)
Not connected
The default installation position of the Q71B is on the lower RS232-B port.
All new RTUs are configured with the correct jumper setting for this.
However, please check this jumper on existing RTUs before using a Q71B.
If using the modem on the RS232-B port, do not apply power from both the
port and the external supply
If the DATRAN RTU is powered from a 24V DC system:
Do not connect the Q71 modem to this 24V DC supply.
Do not connect the Q71 modem to the RS232-B port. Use RS232-A and the
Radios 12V DC supply connected to the Q71 power connector.
Q71B –Quick Start Guide –v1.4 –May 2022
www.qtech.co.nz Ph: +64 3 366 3713 Page 4 of 6
Configuration
The DATRAN RTU must be configured to use the Q71B for communications.
Power up the RTU and connect to QTech Workbench or use Q90 software for older Q03 RTUs.
Navigate to the “Communications” options and set “Device Type” as shown below.
The upper RS232 port is configured in the same way.
XL4 Plus & XL4 RTU Configuration
Q03 RTU Configuration
The default settings are optimised for typical systems and should not need to be changed.
Diagnostics
The Q71B has three status LEDs.
PWR –Power. Green LED is on when power is applied.
RX –Receive. Orange LED in on when radio mute is active.
TX –Transmit. Orange LED is on when RTU is transmitting.
If the Green PWR LED is not on check the power supply and fuse.
The fuse is a 500mA fast blow surface mount fuse.
Audio Signal Level Tuning
This process is performed as part of the factory setup at QTech prior to delivery.
The default signal level is -3 dBm (548mV) into a 600 Ω resistive load.
These steps are included should future calibration or checks be required.
Once the RTU has been configured to use the Q71B, the transmit audio signal level can be adjusted by
pressing the “Set TX Level” button in QTech Workbench or Q90.
This makes the Q71B transmit a continuous tone. To measure the level, use an AC voltage meter across the
pins of the connector labelled “LVL” inside the Q71B.
Turn the potentiometer anti-clockwise to reduce the signal level
Turn the potentiometer clockwise to increase the signal level
Q71B –Quick Start Guide –v1.4 –May 2022
www.qtech.co.nz Ph: +64 3 366 3713 Page 5 of 6
Q71B Jumper Settings
The jumper settings are set by QTech during manufacture. However, if you need to convert the use of a
Q71B please ensure all three jumpers are set correctly.
RTU to Radio –Jumpers aligned towards the “RTU”labels
Base Station - Jumpers aligned towards the “PC”labels
Optional Radio Interface Cables
Optional interface cables are available for legacy analogue radios:
Radio Type Part Number Connectors
Tait T2000 CAB-Q71-T2000 RJ12 to DB9 Male
Tait T500 CAB-Q71-T500 RJ12 to 6 pin Circular DIN Female
Please contact QTech for further details.
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