TB9400/TN9275 Installation and Operation
Installation
89
© Tait International Limited
May 2023
4.6.10
Setting Up Simplex Operation
Simplex operation is not applicable to the TN9275 P25 analog gateway.
Simplex operation allows the base station to use one antenna to either
transmit or receive, so the base station cannot transmit and receive at the
same time. A coaxial relay switches an antenna between base station
receive and transmit automatically.
Simplex operation is supported by analog and P25 modes using P25
firmware, and analog conventional mode using DMR firmware.
In single frequency simplex, only one physical radio frequency is used.
700 MHz operation requires separate receive and transmit frequencies.
While simplex operation is possible, single-frequency simplex is not.
Simplex operation applies to analog, FM and P25 conventional mode with
any conventional line interface: analog line, DFSI, console gateway.
Simplex operates in a single base station context, and simulcast and non-
simulcast channel group operation.
When the base station is transmitting, the receiver is disabled.
Pin 24 in the 25-way D-range is configured as the relay driver. Refer to
Connecting General Purpose Inputs and Outputs
Warning
Switching the PA output while it is operating can dam-
age the PA. It is essential to use a relay that meets the 30 ms operat-
ing time specification.
Warning
When the base station is in simplex mode using a single
antenna with a coaxial changeover relay, the isolation of this relay
must be >40dB to avoid damage to the receiver.
The relay operating time interacts with the base station transmit buffer.
Once a transceiver begins receiving a transit stream, it will not begin
transmitting that signal until the relay operating time has passed. To
avoid any confusion, you must allow at least this much time in the trans-
mit buffer setting (Tx delay for non-simulcast operation, and marshal-
ling duration for simulcast operation).
Tait offers an Antenna Relay Kit TBCA03-10, which comes complete with
installation instructions (402-00119-01).
Configuration
Configure > Base station > Programmable I/O “Antenna relay control”
check box.
