Codan Radio MT-4E Analog and P25 Digital - User Guide - Manual (Page 16)

USER GUIDE | MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS
Chapter 2: Technical Information Page 8
LVDS SERIAL DATA
Codan MT-4E radio modules use Low Voltage Differential Signaling (LVDS) serial data to communicate
between receiver, controller and transmitter modules.
A conventional analog repeater uses analog audio to communicate between the different modules.
Codan MT-4E radio systems use serial data between modules to allow for a completely transparent
digital path between the modules. This means that all digital information is passed through the repeater
system quickly and completely intact.
When an MT-4E Receiver receives a P25 digital transmission, the receiver samples the incoming
information and then creates an LVDS serial data stream (of 257.8 kbps) that contains the same
information as the Common Air Interface (with some overhead data). When an MT-4E Receiver
receives an analog transmission, the receiver samples the incoming information and then creates a
serial data stream (of 257.8 kbps) of the analog information. The incoming frequency and deviation
is converted to serial data through an A/D converter. The MT-4E Transmitter uses this information to
recreate the P25 digital or analog transmission.
ENCRYPTION
The MT-4E Receiver and Transmitter may be purchased with optional DES-OFB / AES encryption
modules installed that will allow decoding and encoding of secure communications. The encryption
modules are required at a base station only, and are not required to repeat an encrypted signal.
CHANNEL SWITCHING RANGE
Although the receiver or transmitter channels can be programmed for any frequency in their band, the
Maximum Switching Range of the module must not be exceeded or the module will require hardware
re-tuning. The maximum switching range of the Receiver modules is +/- 2 MHz (136 - 520 MHz) or
Unlimited (768 - 960 MHz), and the Transmitter modules are Unlimited, unless the VSWR Alarm is used
(+/- 0.5 MHz for VSWR Alarm). For example, a VHF receiver may be programmed for any frequency
between 136 to 174 MHz, but the front end helical fi lter has a typical pass band of 5 MHz, requiring re-
tuning if two frequencies are used that are outside of that pass band.