Jenn Air Modem 1300 User Manual

SPECIALIST RF DESIGNS  
© Copyright Wood & Douglas 2002  
Version: 1.3  
Issue: July 2002  
HERMES RADIO MODEM  
OPERATING INSTRUCTIONS  
(1892 1300)  
LATTICE HOUSE  
BAUGHURST  
BASINGSTOKE  
UK RG26 5LP  
Tel: +44 (0) 118 981 1444  
Fax: +44 (0) 118 981 1567  
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5
6
HARDWARE SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28  
5.1  
5.2  
5.3  
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28  
RS232 Port Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28  
Radio Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29  
MECHANICAL SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30  
6.1.1 Casting Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30  
6.1.2 3U Rack Mounting Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . 30  
6.2  
6.3  
6.4  
Operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32  
Vibration Specifications: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32  
Type Approvals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32  
LIST OF FIGURES  
Figure 1 Timing Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9  
Figure 2 Front View of Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31  
Figure 3 Rear View of Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31  
Figure 4 3U Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31  
LIST OF TABLES  
Table 1 Data Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5  
Table 2 Power Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6  
Table 3 Timing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9  
Table 4 RSSI Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16  
Table 6 Squelch Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18  
Table 7 Power Levels for G-MAX Radios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19  
Table 8 Power Levels for SXn50 Radios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19  
Hermes Operator Note  
Page 3 of 32  
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1
INTRODUCTION  
This document describes the operation of the Wood and Douglas Hermes  
Radio Modem.  
The Hermes modems provide a transparent data link for a wide range of  
applications. The internal modem can be used with a range of Wood &  
Douglas RF products to give great choice in the operating frequency and  
transmit power. Two enclosure types are available to suit different  
applications.  
The Hermes uses 4-Level Frequency Shift Keying (FSK) technology to  
achieve a RF link data rate of 19,200 baud in a 25kHz channel spacing and  
9,600 baud in a 12.5kHz channel spacing.  
One of the radio transceivers (the G-Max family) used inside the Hermes is  
designed for harsh environments and operates over a wide temperature  
range and a high vibration environment.  
The standard Hermes is fitted with the SXn50 range of transceivers. This  
family has products at VHF, UHF and 868MHz, with a maximum transmit  
power of 500mW.  
Hermes Operator Note  
Page 4 of 32  
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2
CONNECTIONS & INDICATIONS  
RS232 Connector  
2.1  
The RS232 connections are made via a 9 way D female with the following  
connections:  
Pin No. Function  
1
CD Output  
Set (+ve) when a RF signal above a certain level is present at the  
RF connector. The threshold is programmable over 10 levels that  
are defined in section 5.13  
2
3
4
RXD RS232 data level data output  
TXD  
DTR  
RS232 level data input  
RS232 level input  
When set (+ve) by the DTE (host processor) the modem and  
transceiver is turned on. The max/min levels are:  
DTR Vin Min.  
DTR Vin Max.  
DTR Vin Min  
DTR Vin Max  
(off state)  
(off state)  
(on state)  
(on state)  
=
=
=
=
-15V  
+2.5V  
+5V  
+15V  
DTR Iin Max(on state)  
Signal Ground  
DSR RS232 level output  
=
4mA  
5
6
Set (+ve) after power is applied to the modem or when the DTE  
(host processor) sets DTR +ve. The output is active when the  
modem is ready to receive data. The time taken for the output to  
become active is <50ms from when DSR or power is applied to  
the modem.  
7
8
RTS  
RS232 level input  
The RTS input must be set (+ve) for both data and configuration.  
Data is ignored when RTS is clear (-ve).  
CTS  
RS232 level output  
Set (+ve) if the transmit RS232 data into the modem can be  
accepted and the RTS input is set, it is cleared (-ve) otherwise.  
Clearing of this signal indicates that the input transmit buffer is  
nearly full .The RS232 data must be stopped within 10 bytes of  
this signal being cleared. After this point the data is ignored. The  
CTS signal is set again if there is room for more than 10 bytes.  
9
n/c  
Table 1 Data Connections  
Hermes Operator Note  
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2.2  
Power Connector  
The power and ancillary connections are made via a 9 way D male  
connector. The power supply input is fully isolated from the chassis of the  
module.  
Note:  
The power supply cannot be used as an RS232 input line.  
Pin No. Function  
1
RSSI Received Signal Strength Output  
Analogue output proportional to the level of the RF input  
Level at -110dBm input = ~0.6V and at -60dBm = ~2.1V  
2
n/c  
3, 4  
+ve Supply Input (9 - 36VDC)  
Receive current <100mA at 24VDC input  
Transmit current <400mA at 1000mW RF output, 24VDC input  
(reverse voltage protection with re-settable "polyfuse")  
5
6
7
8
9
Power Supply Ground (isolated from enclosure)  
I2C Bus Clock (engineering use only)  
0V (chassis of enclosure)  
I2C Bus Data (engineering use only)  
Power Supply Ground (isolated from enclosure)  
Table 2 Power Connections  
2.3  
2.4  
RF Connector  
The RF connection to the modem is a female TNC bulkhead connector.  
Front Panel Indications  
There are 3 LED indicators which show the operation of the unit as follows:  
P
S
Green  
Power On when DC supply input present and DTR input  
is high (> 3V)  
Orange  
Status Flashes orange when the transceiver is switched  
to transmit or receive. Continuous orange if the  
transceiver goes “Out Of Lock” (OOL) which  
happens on failure, or when an invalid frequency  
is programmed into it.  
T
Red TX  
On when the transmitter is turned on.  
These LEDs are next to the connectors on both types of enclosure.  
Hermes Operator Note  
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3
MODEM OPERATION  
Introduction  
3.1  
The internal modem power supply system is turned on/off with the DTR  
input. The modem is ready after an initialisation period. The modem enters  
receive mode using the last set of configuration parameters (RF channel,  
squelch level etc).  
The modem starts the transmit sequence after the first data byte is received  
from the RS232 port. The incoming data is stored while the transmitter is  
turned on and the preamble output. The start, stop and parity (if 8 bit data)  
are stripped off the input data stream and the data stored as 8 bits only.  
The transmission is ended when the input buffer is empty. After the  
transmission is complete and the transmitter turned off, the modem  
switches back to receive mode. Transmission has priority over reception so  
the user has to check by means of the CD handshake line if the radio  
channel is free before inputting data.  
The timing of the power, handshaking and data transfer is shown in Figure 1  
for the G-MAX radio (running at 9600 baud over-air in a 12.5kHz channel)  
and for the SXn50 series of radios (running at 19,200 baud over-air in a  
25kHz channel).  
3.2  
Handshaking Operation During Transmit and Receive  
The DTE must set the RTS input for the modem to accept data. The RTS  
input can be set continuously if no hardware handshake lines are available  
on the DTE. The CTS line must be monitored for data packets greater than  
256 bytes to ensure that input buffer overflow does not occur. If the data  
input is not stopped within 10 characters from the point of buffer overflow,  
the input data will be discarded.  
Handshaking is also required during the code loading.  
The modem starts transmitting when the data is input, regardless of the  
state of the CD output. The DTE must check the CD output prior to data  
transmission. When the CD output is set this indicates that a RF signal is  
present at the antenna. This output is only active when the modem is not  
transmitting.  
Hermes Operator Note  
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3.3  
Data Transfer Modes  
In FEC mode every byte of the data, including the "end-of-file" string is  
scrambled within the modem to ensure that the error correction mechanism  
operates over non-consecutive bits in the data stream. The frame sync  
pattern is not scrambled.  
In non-FEC (High Speed) mode the data is scrambled to minimise problems  
that could occur with many consecutive 1's or 0's in the input data stream.  
3.4  
RS232 Data Handling  
The over-air data rate is faster than the input data rate because only the 8  
data bits of the input character of 11 bits are transmitted. To ensure that no  
data is lost at the output, and for the modem to transmit the data in one  
continuous packet it is essential that the input and output data rates are set  
to at least 2 x the over-air-baud rate. The default over-air baud rate for this  
modem working in a 12.5kHz channel is 9600 baud. For this set the input  
and output RS232 data rates to 19,200. For a 25kHz channel, with an over-  
air baud rate of 19,200, set the data rates to 38,400 baud.  
Some applications running under the Windows™ operating system output  
the data with gaps between single or groups of characters. In some cases  
this can reduce the character rate below the over-air data rate. When this  
occurs, the system will assume that the input data has finished and will turn  
the transmitter off when the input data buffer is empty.  
If more characters are input to the modem while the transmitter is being  
turned off, the transmit process will re-start. This will appear as bursts of  
RF close together. At the receive end, the timing of the data will change as  
there will be gaps in the received data stream.  
This mode of operation ensures that small data packets are transmitted in  
as short a time as possible to reduce the on-air time to a minimum.  
3.5  
Receive-to-Transmit Turnround  
After the last character of a packet of data is output from the receiver, the  
receive system is still processing the “end-of-packet” data. This takes ~5ms  
when in non-FEC mode and ~10ms in FEC mode. During this period the  
processor does not accept any input data. The figures apply for default  
settings: 19,200 baud rate and 4800 symbol/sec over-air baud rate  
Hermes Operator Note  
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Figure 1 Timing Information  
Time (ms)  
G-MAX SXn50  
(9600 baud) (19200 baud)  
Function Description  
t1  
t2  
t3  
t4  
DTR input-to-modem DSR output  
RTS input to CTS output  
<90  
<0.5  
>0.1  
<25  
<25  
<5  
<90  
<0.5  
>0.1  
<25  
<25  
<2.5  
<30  
<45  
<45  
<55  
CTS output to Data input  
Data input to RF output (non-FEC mode)  
Data input to RF output (FEC mode)  
RF output to CD output (at RX end)  
CD output to data output (non-FEC mode)  
CD output to data output (FEC mode)  
Data input to Data output (non-FEC mode)  
t5  
t6  
<30  
<50  
<50  
<75  
t7  
Data input to Data output (FEC mode)  
Table 3 Timing Data  
Hermes Operator Note  
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4
LIST OF COMMANDS:  
Command Mode  
4.1  
The modem is configurable through the RS232 port. The Command Mode  
has to be activated to do this, as detailed in the following paragraphs:  
4.1.1 Activation of the Command Mode:  
The Command Mode is activated with the string:  
<wait>+++<wait> <CR><LF>  
Where <wait> is a programmable period after transmitting data (which is set  
by register S154) which has a nominal value of 10ms.  
The modem responds with:  
OK<CR><LF>  
The modem is now ready to be configured. Transmitting or reception is  
blocked during Command Mode.  
If the "+++" string is input without a <CR><LF> then the string is transmitted  
as normal data. Note that one or more consecutive “+” characters in the  
input data are held in the modem until it is determined that it is not a “+++”  
string.  
The configuration mode is only accepted if the RTS line is set. The “+++”  
string is only accepted if this string is the first three characters and there has  
been no data for greater than the time set by register S154.  
The +++ string is only transmitted over the air if embedded in a data string as  
described above.  
Important: any configuration changes made are only saved to the  
non-volatile memory after a write command (AT &W).  
Note that the communication parameters (baudrate etc) are the programmed  
parameters.  
Hermes Operator Note  
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4.1.2 Ending of Command Mode  
The command mode is ended by inputting the string:  
ATO<CR><LF>  
The modem responds with:  
OK<CR><LF>  
The modem is now ready for normal modem operation.  
Note that the communication parameters (baudrate etc) are the programmed  
parameters.  
4.2  
Command Syntax  
4.2.1 Note: Capital letters MUST be used for all command instructions.  
4.2.2 All syntax commands with multiple ‘n’ ‘s accept multiple formats. For  
example, if ‘nnn’ is specified in the command string, then the following will  
be valid:  
1
01  
001 or  
or  
or  
+1  
+01  
+001  
4.2.3 The commands for reading registers have the form:  
AT S158?<CR><LF>  
The answer to this query is:  
nnn<CR><LF>  
4.2.4 After setting a parameter the modem responds with:  
OK<CR><LF>  
ERROR<CR><LF>  
if a valid entry and  
if an invalid entry  
Hermes Operator Note  
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4.3  
Baud Rate (AT B0)  
When the baud rate is changed, the change is made after the Command  
Mode is ended (with the AT O command).  
The baud rate is set with the following command:  
Baud Rate  
Where:  
AT B0=n <CR><LF>  
n = 1 4800  
n = 2 9600  
n = 3 19200  
n = 4 38400  
Default:  
Read:  
n = 3 for 12.5kHz radios  
n = 4 for 25kHz radios  
AT B0?<CR><LF>  
Note:  
this shows the new value, even though the change is  
not implemented until the Command Mode is exited.  
Read Return: n<CR><LF>  
Example:  
AT B0=2<CR><LF>  
for 9600 baud  
4.4  
Parity (ATB1)  
The number of data bits is fixed to 8. Parity at the RS232 input to the  
transmitter has no effect and is not transmitted. The 8 data bits can be used  
to transmit 7 data bits + 1 parity bit. In this case the modem has to be set to  
no parity.  
The number of stop bits at the RS232 input to the transmitter can be 1 or  
more. The number of stop bits at the receiver RS232 output is fixed at 1. This  
is to avoid congestion of the output data.  
When the parity is changed, the change is made after Command Mode is  
ended (with the AT O command).  
The parity is set with the following command:  
Parity  
AT B1=n<CR><LF>  
Where:  
n = 1 even  
n = 2 odd  
n = 3 none  
Default:  
Read:  
3
AT B1?<CR><LF>  
Note:  
this shows the new value, even though the change is  
not implemented until the Command Mode is exited.  
Read Return: n<CR><LF>  
Example: AT B1=n<CR><LF>  
Hermes Operator Note  
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4.5  
Format Mode (AT F)  
This command turns the Forward Error Correction (FEC) mode on and off.  
The over-air format allows for higher speed operation, but with reduced Bit  
Error Rate (BER) performance with the FEC turned off, or lower speed,  
improved BER with the FEC turned on.  
Figure 1 and the associated table give the timing information for both modes  
of operation.  
The command is:  
Format mode AT F=n<CR><LF>  
Where  
n=0 mode with FEC  
n=1 high speed mode without FEC  
Default:  
Read:  
n=1  
(non-FEC mode)  
AT F?<CR><LF>  
Read Return: n<CR><LF>  
Example: AT F=1<CR><LF>  
Hermes Operator Note  
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4.6  
Engineering Test Modes (AT In)  
Format modes:  
To enable the function  
To disable the function  
Modem responds with  
Read status:  
AT In=1 <CR><LF>  
AT In=0 <CR><LF>  
OK <CR><LF>  
AT In?<CR><LF>  
Modem responds with  
m <CR><LF>  
where m=0, not active  
m=1, active  
Where  
n = 2 Output Continuous Preamble (used for  
checking transmitter and receiver). The  
preamble is transmitted until stopped by the  
ATI2=0 or AT I=10 commands, or ending the  
command mode. Note: for a G-Max, this test  
must not be run for >10 minutes as damage to  
the transceiver may occur.  
n = 3 Output a series of 49 byte long data packets  
with a programmed period between each  
packet set with register S162. The message  
data sent is: “The quick brown fox jumps over  
the lazy dog.<CR><LF>” Each line of data is  
pre-ceded by “XX “ where XX is a line number  
which increments from 00 - 99.  
The data is transmitted until stopped by the  
ATI3=0 or AT I=10 commands, or ending  
command mode.  
n = 4 Adds the Output Data quality and Signal level  
data to the end of each received data packet.  
This is ended by the ATI4=0 or AT I=10  
command. The data format is:  
R:XX, D:XXX<CR><LF>  
where XX = 1 - 10 and XXX = 66 - 256 as  
defined in paragraphs 5.10 and 5.12  
Note: if data is received before the values have  
been read then R:XX, D:XXX<CR><LF> will be  
output.  
n = 9 Gives information about the software version  
(refer to paragraph 5.7).  
n = 10 Turn off test modes  
Hermes Operator Note  
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4.7  
Software Version Information (AT I9)  
This command tells the modem to output information about the software  
version.  
Example:  
or  
ATI9=1<CR><LF>  
ATI9<CR><LF>  
return software version  
Return:  
‘an ASCII string detailing the ID and versions of the  
internal processors’ <CR><LF>  
An example of the return data is as follows:  
Files:  
Main micro:"QL3z10", Ver.:1.01.05, Date:31/10/2001  
Slave micro:"Slave",Ver.:0.00.02, Date:12/11/20001  
Flash Programmer:"karfl3", Ver.:1.00.03, Date:24/10/2001  
Hermes®, © 2001, Wood & Douglas Ltd.  
4.8  
Command Mode Guard Time (AT S154)  
To enable the transmission of the command sequence within a packet of  
data, a guard time is placed around the command sequence. If the gap  
between the characters in the command mode string is less than this guard  
time, then the data string is assumed to be part of the data. This includes  
the gap between the last received data byte and the first “+”. The command  
is:  
AT S154=nnn<CR><LF>  
Where  
Default:  
Read:  
nnn =0 to 255 ms  
10  
AT S154?<CR><LF>  
read the setting  
Read Return: nnn<CR><LF>  
Example: AT S154=10<CR><LF> set 10 msec time delay  
4.9  
Centre Radio Frequency (AT S155)  
The channel change system for the Hermes is based around a centre  
frequency. The Hermes is programmed with a factory set centre frequency  
that is the centre of the RF switching band. The channel change is carried  
out by programming a channel step size (typically 12.5kHz) and setting 00-99  
above or 00-99 channels below the centre frequency. The centre frequency  
can be changed and stored in EEPROM for moving the programmed  
channels. A temporary change can also be made by storing a new centre  
frequency in RAM. This is not restored if power is lost to the unit.  
Hermes Operator Note  
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The centre radio frequency of the modem is set as follows:  
AT S155=nnn.nnnnnn<CR><LF>  
Where:  
nnn.nnnnnn is the format of the input string for the  
frequency in MHz  
Default:  
Read:  
current centre frequency.  
AT S155?<CR><LF>  
Read Return: nnn.nnnnnn<CR><LF>  
Example: AT S155=458.5<CR><LF> sets 458.5MHz  
AT S155=458.500000<CR><LF> sets 458.5MHz  
Note that frequencies in multiples of either 12.5kHz or 10kHz only are  
acceptable. If a whole number of MHz is entered a “.” must be entered  
before the <CR><LF>.  
If the wrong centre frequency is entered the modem will respond with the  
following error message and the entry will be ignored:  
ERROR<CR><LF>  
4.10 Received Signal Strength Indication (RSSI) (AT S156)  
This request to the modem gives a response of nn <CR><LF>, where the nn  
is the value of the Received Signal Strength of the radio carrier present at the  
antenna at that time. The returned value of RSSI is in the range of 1 to 10.  
The level of RF level of each value is given in the following table:  
RSSI Level  
Level at RF Input ( dBm ±2dB)  
-114 to -120  
-108 to -114  
-102 to -108  
-96 to -102  
-90 to -96  
01  
02  
03  
04  
05  
06  
07  
08  
09  
10  
-84 to -90  
-78 to -84  
-72 to -78  
-66 to -72  
> -66  
XX  
Not available  
Table 4 RSSI Levels  
Hermes Operator Note  
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The RSSI level is requested with the command:  
AT S156?<CR><LF>  
Read Return: nn<CR><LF>  
The data can be added to the end of each received packet as defined in  
paragraph 5.6.  
4.11 Radio Channel (AT S157)  
The radio transceiver is programmed with a centre frequency (using the AT  
S155 command). This frequency is set up in the factory at the centre of the  
RF switching bandwidth. Once programmed with this frequency a Channel  
Step Size (using AT S161 command) can be programmed. ±99 channels  
can then be set with this command to give a total of 199 frequencies.  
The command for setting the radio channel is  
AT S157=n<CR><LF>  
Where:  
Default:  
Read  
n = ±0 to ±99  
0 (which is printed on screen as +00)  
AT S157?<CR><LF>  
Read Return: ±nn<CR><LF>  
Example:  
AT S157=-10<CR><LF> sets the channel to -10  
4.12 Data Quality (AT S158)  
This request for data gives an indication of the quality of the data reception.  
The signal quality is read from the modem system at the end of each  
received packet and stored to give a consistent result when the quality is  
requested. The value is in the range 64 to 255, the larger the value, the  
higher the quality. The command for requesting the data quality is  
AT S158?<CR><LF>  
Read Return: nnn<CR><LF>  
If no data has been received, XXX is returned.  
The data can be added to the end of each received packet as defined in  
paragraph 5.6.  
Hermes Operator Note  
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4.13 Squelch (AT S159)  
This command sets the squelch threshold to one of 10 pre-set levels as  
shown in the Table 6.  
This command enables the user to reduce the chances of local interference  
showing the channel to be busy which could reduce the occupancy of the  
system.  
Squelch Level  
Level at RF Input  
( dBm ±2dB)  
1
2
< -112  
-110 to -112  
-108 to -110  
-105 to -108  
-103 to -105  
-101 to -103  
-99 to -101  
-97 to -99  
-95 to -97  
> -95  
3
4
5
6
7
8
9
10  
Table 6 Squelch Levels  
The command for setting the squelch is  
AT S159=n<CR><LF>  
Where:  
Default:  
Read  
n = squelch threshold with value 1 to 10  
2
AT S159?<CR><LF>  
Read Return: nn<CR><LF>  
Example: AT S159=10<CR><LF> sets the squelch to 10  
Hermes Operator Note  
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4.14 Transmission Power (AT S160)  
The command enables the RF transmit power to be modified. Different RF  
units have different capabilities and may change, depending on what is  
supplied.  
The SXn50 range of transceivers have 2 levels only. The levels for the 1W  
and 2W versions of the G-MAX are shown in Table 7. Table 8 shows the 2  
levels for the SXn50 range.  
Output Power for 1W G-MAX  
Output Power for 2W G-MAX  
Power  
Level  
mW  
dBm  
Tolerance  
(dB)  
mW  
dBm  
Tolerance  
(dB)  
(nominal) (nominal)  
(nominal) (nominal)  
1
2
16  
25  
12  
14  
16  
18  
20  
22  
24  
26  
28  
30  
±3  
31  
50  
15  
17  
19  
21  
23  
25  
27  
29  
31  
33  
±3  
±3  
±3  
3
40  
±3  
79  
±3  
4
63  
±1.5  
±1.5  
±1.5  
±1.5  
±1.5  
±1.5  
±1.5  
126  
200  
316  
500  
794  
1260  
2000  
±1.5  
±1.5  
±1.5  
±1.5  
±1.5  
±1.5  
±1.5  
5
100  
158  
251  
398  
631  
1000  
6
7
8
9
10  
Table 7 Power Levels for G-MAX Radios  
Output Power  
Power  
mW  
dBm  
Tolerance  
(dB)  
Level  
(nominal) (nominal)  
1
2
5
7
±3  
500  
27  
±1.5  
Table 8 Power Levels for SXn50 Radios  
Hermes Operator Note  
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The power is set with the command:  
AT S160=n<CR><LF>  
Where:  
Default:  
Read  
sets the power threshold <1 to 10>  
10  
AT S160?<CR><LF>  
Read Return: nn<CR><LF>  
Example:  
AT S160=-10<CR><LF> sets the power level to 10  
4.15 Channel Step Size (AT S161)  
This command sets the channel step size. The basic reference frequency for  
the radio is either 12.5KHz or 10KHz, giving possible frequency channel  
steps of 10kHz, 12.5kHz, 20kHz and 25kHz. The Channel Step Size is set  
with the command:  
AT S161=n<CR><LF>  
Where:  
n=1 10 kHz  
n=2 12.5 kHz  
n=3 20 kHz  
n=4 25 kHz  
Default:  
Read:  
n=2 (12.5 kHz)  
AT S161?<CR><LF>  
Read Return: n<CR><LF>  
Example:  
AT S161=1<CR><LF> sets 10 kHz channel step  
If a channel step size is entered which is not a multiple of the centre  
frequency an error is returned and the entry ignored. This is to ensure that  
only valid frequencies on multiples of the channel step size are allowed  
based on the centre frequency entered. The error message is of the form:  
ERROR<CR><LF>  
4.16 Test Message Period (AT S162)  
This command sets the period between sending the test message. The  
command is:  
AT S162=n<CR><LF>  
Where:  
Default:  
Read:  
n=1 - 255 in 10ms steps  
n=10 (100ms)  
AT S162?<CR><LF>  
Read Return: nnn<CR><LF>  
Example: AT S162=100<CR><LF>  
sets 1 second period  
Hermes Operator Note  
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4.17 Over-Air Symbol Rate (AT S163)  
Note: engineering function only.  
This command sets the over-air baud rate to enable the modem to be used  
with different radios and channel spacings. The command format is:  
AT S163=n<CR><LF>  
Where:  
Default:  
Read  
n = 2  
n = 3  
n = 2  
n = 3  
4800 symbols/sec  
9600 symbols/sec  
4800 for 12.5kHz radios  
for 25kHz radios  
AT S163?<CR><LF>  
Read Return: n<CR><LF>  
Example:  
AT S163=3<CR><LF> sets 9600 symbols/sec  
4.18 Preamble Period (AT S165)  
Note: engineering function only.  
This command enables the number of preamble blocks (each block equals 6  
bytes) that are transmitted before each data packet to be changed. This  
preamble allows for the rise time of the transmitter as well as the minimum  
number of blocks required by the receiver. This allows the system  
performance to be changed to enable the modem to be used with different  
transceiver equipment. The command format is as follows:  
AT S165=n<CR><LF>  
Where:  
Default:  
Read  
n = 1 - 10 blocks  
n = 2  
AT S165?<CR><LF>  
Read Return: nn<CR><LF>  
Example:  
AT S165=10<CR><LF> sets a preamble of 11 blocks  
Note that a symbol period depends on the RF baud rate (as set by paragraph  
4.17).  
For the G-MAX radio at 9600 symbols per second n = 2.  
For the SXn50 radio at 19200 symbols per second n = 14.  
Hermes Operator Note  
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4.19 Frame Synch Tolerance (AT S166)  
Note: engineering function only.  
This command controls a receive function within the FX929 modem IC within  
the modem.. The command format is as follows:  
AT S166=n<CR><LF>  
Where:  
n = 0  
n = 1  
n = 2  
n = 3  
n = 0  
0 mismatches allowed in frame synch.  
pattern  
2 mismatches allowed in frame synch.  
pattern  
4 mismatches allowed in frame synch.  
pattern  
6 mismatches allowed in frame synch.  
pattern  
Default:  
Read  
0 mismatches allowed in frame synch.  
pattern  
AT S166?<CR><LF>  
Read Return: n<CR><LF>  
Example:  
AT S166=2<CR><LF> sets 4 mismatches allowed  
4.20 Invert Symbol (AT S167)  
Note: engineering function only.  
This command controls the polarity of the transmit and receive audio  
between the FX929 modem IC and the transceiver and allows for different  
transceivers to be used with the modem. The command format is as follows:  
AT S167=n<CR><LF>  
Where:  
n = 0  
n = 1  
n = 2  
n = 3  
n = 0  
RX non-inverted and TX non-inverted  
RX non-inverted and TX inverted  
RX inverted and TX non-inverted  
RX inverted and TX inverted  
Default:  
Read  
RX non-inverted and TX non-inverted  
AT S167?<CR><LF>  
Read Return: n<CR><LF>  
Example: AT S167=1<CR><LF> RX non-inverted and TX  
inverted  
Hermes Operator Note  
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4.21 Squelch Delay (AT S168)  
Note: engineering function only.  
This command changes the delay between the Squelch being received and  
the FX929 modem IC looking for preamble in the receive audio. This allows  
the modem to be used with different transceivers. The command format is  
as follows:  
AT S168=n<CR><LF>  
Where:  
Default:  
Read  
n = 1 - 255 (ms)  
n = 10  
AT S168?<CR><LF>  
Read Return: nnn<CR><LF>  
Example:  
AT S168=10<CR><LF> 10ms delay between squelch  
and preamble  
4.22 Enable/Disable Receive Output Data (AT &D)  
This command disables output of any received data.  
Note that the CD output continues to operate when the data output is  
disabled. The command is of the format:  
AT &D=n<CR><LF>  
Where:  
n=0 disable output  
n=1 enable output  
n=1 (enabled)  
Default:  
Read:  
AT &D?<CR><LF>  
Read Return: n<CR><LF>  
Example:  
AT &D=1<CR><LF>  
enables receiver data output  
4.23 Enable/Disable Input Echo Data (AT &E)  
This command enables/disables input echo on the screen. The command is  
of the format:  
AT &E=n<CR><LF>  
Where:  
n=0 disable echo  
n=1 enable echo  
n=1 (enabled)  
Default:  
Read:  
AT &E?<CR><LF>  
Read Return: n<CR><LF>  
Example: AT &E=1<CR><LF>  
enables echo input  
Hermes Operator Note  
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4.24 Radio Frequency (AT &F)  
The Hermes is programmed with a factory set centre frequency that is the  
centre of the RF switching band. A new frequency can be entered directly  
within the ±99 channels of the centre frequency using this command. The  
channel number is re-calculated for the frequency entered using this  
command.  
The radio frequency of the modem is set as follows:  
AT &F=nnn.nnnnnn<CR><LF>  
Where:  
nnn.nnnnnn is the format of the input string for the  
frequency in MHz  
none  
AT &F?<CR><LF>  
Default:  
Read:  
Read Return: nnn.nnnnnn<CR><LF>  
Example: AT &F=458.5<CR><LF> sets 458.5MHz  
AT &F=458.500000<CR><LF> sets 458.5MHz  
Note that frequencies in multiples of either 12.5kHz or 10kHz only are  
acceptable. If a whole number of MHz is entered a “.” must be entered  
before the <CR><LF>.  
If the frequency entered is outside the ±99 channels, or the frequency is  
invalid, the modem responds with the following error message and the entry  
is ignored:  
ERROR<CR><LF>  
4.25 Save parameters (AT &W)  
To permanently store any parameter changes, the parameters are saved in  
non-volatile memory. The command for this is:  
AT &W<CR><LF>  
4.26 Restore defaults (AT &Y8)  
To quickly check the operation of the modem, the factory settings can be  
loaded. If required the AT &W save command can be used to save the  
defaults. The command for this is:  
AT &Y8<CR><LF>  
Hermes Operator Note  
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4.27 Display parameters (ATT?)  
Displays all the AT settings. The command for this is:  
ATT?<CR><LF>  
The modem responds with:  
2, 3, 0, 010, 429.850000, XX, +00, XXX, 02, 05, 2, 020, 2, 08, 0, 0,  
050, 1, 429.850000 <CR><LF>  
The order of the data is:  
2
3
0
baud rate  
parity  
format mode  
010 command mode guard time  
429.850000 centre frequency  
XX  
RSSI (if no received data, 1 - 10 otherwise)  
+00 radio channel  
XXX data quality (if no received data, 66 - 256  
otherwise)  
02  
05  
2
squelch  
power  
channel step size  
020 test message period  
2
08  
0
over air baud rate  
preamble blocks  
frame synch. tolerance  
invert symbol  
0
050 squelch delay  
1
enable/disable receive data output  
429.850000 radio frequency  
Note: where no data has been received to provide the data, or the command has  
not been enabled, X is displayed.  
Hermes Operator Note  
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4.28 Code Loader (AT S2000)  
Warning  
once activated, a code load must be carried out  
DO NOT enter unless you wish to carry out a code load  
This command enables the firmware contained within the modem to be  
upgraded using a simple terminal program. The baud rate for the link is fixed  
at 19,200 baud with no parity.  
The command for this is:  
AT S2000<CR><LF>  
The modem responds with:  
Flash Programmer:"karfl3", Ver.:1.00.03, Date:24/10/2001  
To update firmware, upload Hermes upgrade *.hex file using  
a terminal program that can send 8 bit binary data.  
Hermes®, © 2001, Wood & Douglas Ltd.  
When this message has been output the code loader software is ready for  
the new code data to be uploaded. As each line of code is accepted the  
modem responds with one of 4 responses:  
“.”  
“:”  
“P”  
“E”  
line written into program memory successfully  
line written into EEPROM memory successfully  
attempt to write into protected memory area, no action taken  
error in writing to memory area  
Hermes Operator Note  
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A typical programming sequence display is as follows:  
PPPPP...........................................................................  
................................................................................  
................................................................................  
................................................................................  
................................................................................  
................................................................................  
..........................................PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP  
PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP.::::  
:
Flash Programming Successful!!  
Hermes®, © 2001, Wood & Douglas Ltd.  
Apply a DC reset to the modem before using the modem.  
If an error in the data is received the modem responds with:  
Flash Programming Failed!!  
Hermes®, © 2001, Wood & Douglas Ltd.  
If power is lost or some other problem occurs before the upload is  
completed, the next time the modem is powered on it automatically requests  
new data by outputting the above message. This repeats until the code load  
is successful.  
Hermes Operator Note  
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5
HARDWARE SPECIFICATION  
Introduction  
5.1  
The hardware of the modem part of the system is based on the FX929B  
modem chip from Consumer Microcircuits Ltd (CML). The radio part of the  
system can be either the G-MAX "rugged" transceiver, or the lower power  
SXn50 range of transceivers. The interface between the outside world and  
modem chip is controlled by a microprocessor.  
The two types of transceiver are separate modules which is mounted onto  
the modem PCB.  
The Hermes is supplied in 2 different mechanical versions. One of these  
uses a rugged enclosure suitable for wall mounting. The second version is  
housed in a 3U high “euro” cassette for mounting in a standard 19" rack.  
5.2  
RS232 Port Parameters  
The communication with the host processor is via a standard RS232 port.  
The data levels are as per the RS232 specification with logic '0' being a  
positive voltage.  
The programmable parameters for the transmit and receive ports are:  
Baud rates  
Data bits  
4800/9600/19200/38400  
8 (note that 7data bits plus parity = 8 data bits with no  
parity)  
Parity  
Odd, Even or None  
Stop bits  
Receiver output = 1  
Input to transmitter = 1 or more  
Hermes Operator Note  
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5.3  
Radio Specifications  
The transceiver specifications are detailed in the appropriate handbook for  
the SXn50 family and the G-Max. Throughout the handbook, the differences  
between the two types of transceiver have been highlighted.  
A brief summary of the maion characteristics are listed below:  
Parameter  
G-Max  
SXn50  
TX Power  
500mW with 100% duty  
cycle  
Hi Power setting 500mW  
with 100% duty cycle  
1W with maximum duty  
cycle of <50%  
Lo Power setting = 5mW  
2W with maximum duty  
cycle of 20%  
(10 programmable levels)  
SX150  
SX450  
SX850  
140 - 200MHz  
390 - 490MHz  
868 - 870MHz  
340 - 360MHz  
400 - 470MHz  
Operating Frequencies  
Switching bandwidth  
(frequency range over  
which unit can operate  
without adjustment)  
SX150  
SX450  
SX850  
4 MHz  
8 MHz  
2 MHz  
8MHz  
Alignment bandwidth  
(frequency range over  
which unit can operate  
with adjustment)  
SX150  
SX450  
SX850  
20 MHz  
20 MHz  
2 MHz  
20MHz  
Hermes Operator Note  
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6
MECHANICAL SPECIFICATION  
Enclosures  
6.1  
6.1.1 Casting Enclosure  
The casting enclosure is shown in Figure 2. The enclosure has 4 off M4  
fixings. There are raised bosses on the base of the unit to enable water to  
run underneath the unit when mounted on a vertical surface. Figure 3  
shows the connector layout under the protective casting overhang which  
prevents any water ingress when mounted vertically. The lid has an IP65  
rated gasket to ensure no water ingress. The outline dimensions of the  
casting are:  
169.3 x 129.2 x 38.5mm (6.67" x 5.09" x 1.52")  
The weight of the unit using a G-MAX radio is ~612g (21.6oz).  
The weight of the unit using a SXn50 radio is ~600g (21oz).  
6.1.2 3U Rack Mounting Enclosure  
The modem can also be supplied in a 3U high, 5HP wide by 101mm, rack  
mount enclosure, as shown in Figure 4.  
The weight of the unit using a G-MAX radio is ~580g (20.5oz).  
The weight of the unit using a SXn50 radio is ~560g (20oz).  
Hermes Operator Note  
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Figure 2 Front View of Casting  
Figure 3 Rear View of Casting  
Figure 4 3U Enclosure  
Hermes Operator Note  
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6.2  
Operating conditions  
Operating temperature:  
Storage temperature: -  
Relative humidity:  
-25 - + 55° C  
30 - + 70° C  
20- 80% non-condensing  
6.3  
6.4  
Vibration Specifications:  
When the G-MAX transceiver is used the casting version of the modem  
meets the MIL-STD-810E:514.4 specification.  
Type Approvals  
The equipment meets the requirements of the following specifications:  
EMC:  
Type Approval:  
ETS 300 279  
ETS 300 113.  
Low Voltage Directive: Directive 73/23/EEC  
A Technical Construction File is being prepared which will be reviewed by a  
Notified Body to ensure that all the requirements of the R&TTE directive have  
been met.  
Hermes Operator Note  
Page 32 of 32  
Wood & Douglas Ltd  
Lattice House, Baughurst Road, Tadley Hants RG26 5LP  
Tel: +44(0) 118981 1444. Fax: +44(0) 118981 1567  
1892 1300  
1.3/July 2002  
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