Racom MR400 User Manual

Table of Contents

Introduction .................................................................................................................................................. 3

1. Radio Modem MR400 ............................................................................................................................. 4

Radio Part MR400 ......................................................................................................................................... 5

Modem Part ............................................................................................................................................ 5

3. MR 400 Connectors ...................................................................................................................................... 6

Antenna .................................................................................................................................................... 6

Serial Interface ....................................................................................................................................... 6

RS232, RS422 and RS485 Connectors..................................................................................... 6

Distinguishing Data Modules by Colour .......................................................................................... 6

Ethernet .................................................................................................................................................... 7

Analog and Binary Inputs and Outputs .......................................................................................... 7

Labelling ........................................................................................................................................... 7

Parameters ..................................................................................................................................... 7

Supply Connector ....................................................................................................................................... 8

Information LED .................................................................................................................................. 8

Service Connector ................................................................................................................................ 9

4. Table of Technical Parameters .............................................................................................................. 10

5. Dimensional Diagram .............................................................................................................................. 11

6. Labelling Radio Modems ....................................................................................................................... 12

7. Conditions for MR400 Operation ............................................................................................................ 13

Radio modem instalation and maintenence ................................................................................................ 13

Conditions of Liability for Defects and Instructions for Safe Operation of Equipment ............................ 14

Declaration of Conformity ......................................................................................................................... 15

Limitations of Use ...................................................................................................................................... 16

List of Figures

1. Radio modem MR400 .............................................................................................................................. 3

3.1. Service connector connections .......................................................................................................... 9

3.2. View of radio modem – description of connectors, model with DSUB (Canon)

connectors and with terminals .................................................................................................................... 10

5.1. Mechanical dimensions of MR400 .................................................................................................. 12

6.1. Serial codes of products ....................................................................................................................... 13

List of Tables

3.1. Table of data cable connections ........................................................................................................ 7

3.2. Table for distinguishing LEDs for RxD and TxD by colour ....................................................... 7

3.3. Table of Ethernet to cable connector connections ....................................................................... 8

3.4. Table of digital and analog input and output parameters ........................................................... 8

3.5. Table of service connector connections .......................................................................................... 9

4.1. Table of technical parameters ............................................................................................................. 13

Introduction

This operator manual serves as the primary document for familiarising users with the parameters of the radio modem, its
properties, modifications and with the parameters of interfaces. In order to master all the functions of the radio modem
and the MORSE system you should refer to other documents.

Figure 1. Radio modem MR400 (MR300, MR160)

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1. Radio Modem MR400 (MR300, MR160)

MR 400, MR300 and MR160 are conceptually new radio modems designed for transmitting data in the VHF and UHF
bands. The radio modem uses 4-state FSK modulation providing for a maximum signalling rate of 21.68 kbit/s. The
radio modem is of modular design with one to four standard RS232 ports (an RS422 or RS485 port can be used in
place of two of them) available to the user. The configuration can be extended by an Ethernet interface and also by a
module with analog and digital inputs/outputs, which is normally provides two analog inputs and outputs and two
digital inputs and outputs. The radio data transceiver module can be configured to an arbitrary frequency of the
transmitter and receiver within the 3.2 MHz frequency range in a 12.5 kHz channel raster. The receiving and
transmitting frequencies are mutually independent and are derived from the frequencies of four Phase-Locked Loops
programmed by the transceiver microprocessor. Channel settings are stored in the transceiver EEPROM memory and
the FLASH memory module of the modem whose central processor controls the operation of the transceiver
microprocessor. The RF output power of the radiomodem transmitter’s high frequency signal is software-configurable
in sixteen steps from 0.1 to 5 W. The software configuration of MR400 is backward compatible with that of the MR25
radio modem. A description of software control and configuration of the MR25 is available in publications describing
MORSE Firmware.

Important

ATTENTION! The radio modem is equipment which can only be operated in the Czech Republic on the basis
of Permission to operate transmitting radio stations issued by the Department of Frequency Spectrum
Management at the Czech Telecommunication Office.

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2. Description of Functions

Radio Part MR400

The architecture of MR400 (MR300, MR160) radio modems resolves most of the requirements placed on a top
quality user friendly radio modem with a very short switching time between receiving and transmitting.
Frequency synthesis enables software selection of an arbitrary channel from the given frequency range. The
operation of the radio part is controlled and diagnosed by the microcontroller. The receiving part of the radio
modem is a double-conversion superheterodyne. The overall selectivity is divided between both intermediate
frequency levels. The first filter carries out the necessary channel pre-selection which ensures the linear function
of the following second mixer and intermediate frequency amplifier. The second filter has the attenuation
characteristic necessary for channel selection in the used channel spacing of 25 kHz (12.5 kHz). Logic circuits,
switching the radio part between modes of receiving and transmitting, have high noise immunity and switch
respective blocks sequentially. This minimises transient parasite states and optimises bandwidth during
switching. Switching to the transmitting mode is blocked when the frequency synthesiser is out of lock or the
internal temperature exceeds a hardware set limit or the supply voltage falls below the value ensuring proper
functioning of the device.

Modem Part

The control microcomputer has 4 MB of FLASH memory and 16 MB of RAM memory available. The battery
backup-ed real-time clock, detector of supply voltage failure and watch-dog circuits belong amongst the other
circuits of this block. If there is a supply voltage failure the fact is recorded into memory with the respective
timestamp thanks to the charge stored in electrolytic capacitors. The user therefore has information available
about the time and duration of possible faults caused by power failures. It is possible to connect equipment with
signalling rates up to 115.2 kbit/s to the modem via the RS232 data interface. RS232 interface converters are
protected against overvoltage with TRANSIL elements. A lithium battery is used for backing up in the modem
part.

Important warning – a risk of explosion!

The lithium battery must not be replaced by an incorrect type. When in doubt, leave the replacement to
the manufacturer.

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3. MR 400 Connectors

Antenna

The antenna connector is of the N type, female, impedance 50 Ohm. The antenna cable must be fitted with an
appropriate mate. We recommend using the RG213 50 Ohm cable. The H1000 cable should be used when the
length of the antenna feeder exceeds 25 m.

Important

CAUTION. The radio modem should be powered only when the antenna (or artifical load) is
connected. Otherwise it could lead to damage to the radio part of the modem.

Serial Interface

According to the configuration of the radio modem it is possible to use a terminal block or DSUB 9 (Canon)
connectors for connecting data cables via the serial interface. See Chapter 6 Labelling radio modems.

RS232, RS422 and RS485 Connectors

Table 3.1. Table of data cable connections

Terminals RS232 DSUB9F RS422 Canon RS422

1 CTS 8 TxD- 7
2 RTS 7 TxD+ 3
3 RxD 2 RxD- 8
4 TxD 3 RxD+ 2
5 GND 5 GND 5

When RS485 interface is needed, the RS422 pin layout applies. It is necessary to shortcut TxD- to RxD- and
Txd+ to RxD+ to obtain the respective Data-, Data+ RS485 signals.

Distinguishing Data Modules by Colour

For RS232 RxD is the output from the radio modem (approx. -8V when inactive) and TxD is the input to the
radio modem (according to the RS 232 standard). Hardware versions of the interface can be distinguished
according to the colours of LED diodes next to the connector.

Table 3.2. Table for distinguishing LEDs for RxD and TxD by colour

Type of interface Colour (RxD / TxD)

RS232 red / green

RS232 optically coupled orange / green

RS422/485 optically coupled orange / yellow

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