SR450 RECEIVER OPERATING INSTRUCTIONS
1892 1128
These operating instructions are intended to provide the user with sufficient information to install and operate the module correctly.
The Wood & Douglas SR450 receiver is intended to fulfil the numerous OEM
applications by virtue of its highly flexible design approach, miniature size and cost-effective performance. The unit complies with MPT1329 and as such does not require an operating licence in the UK. It is also approved to various EC specifications. VARIANTS FREQUENCY RANGE (MHZ) CHANNEL SPACING 12.5kHz 20kHz 25kHz 430 - 450 31 32 33 450 - 470 51 52 53
The SR450 is available in two frequency bands and channel spacings as detailed in the table. The code designations form part of the product variant type given on the label fixed to the top screening cover of the module.
INSTALLATION
The SR450 is intended to fit easily and with minimum space requirements into the user's own equipment housing. The complete module is housed within a tin-plated enclosure and is secured by means of four No 4 self-tapping screws which locate in the four corners through the lower screening cover. DO NOT overtighten these screws during assembly.
CONNECTIONS
The radio antenna connects by means of a SMB miniature coaxial connector. All other connections to the SR450 receiver are made using a standard 9-way D type connector (PL1) or a 10 way header PL2 as detailed in the table below.
D-TYPE PL1
10-WAY
PL2 NAME FUNCTION REMARKS
1 1 0V supply 0 volts common ground
2 3 SQF squelch output
(open collector)
50mA NPN to ground (ON under no signal conditions). Internal 10kS pull-up to 5V 3 5 RSSI S meter output
(optional)
0 to 3V output proportional to the received RF signal level. Rout =1kS
4 7 AUDIO audio output
600mV p/p AC coupled Rout = 1kS
Note: the output audio is inverted with respect to the ST450 (or similar Wood & Douglas product) audio input
5 9 +Vin + positive supply +6V to +15V nominal
6 2 CS0 channel select
(LSB)
high >4V (or floating internal pull-up), low <0.8V,
7 4 SQ DIS squelch disable leave floating for normal operation
0V (or <0.5V) inhibits all squelch operation
8 6 CS1 channel select
(MSB)
high >4V (or floating internal pull-up), low <0.8V RS232 level serial programming input Note: Inverted TTL level data can also be used.
If not used, leave not connected or connect to 0V
9 8 RXE receiver enable
(active low)
high >4V (or floating) Receiver OFF low <1V Receiver OPERATIONAL
-CHANNEL SELECTION
The SR450 offers one of 4 channels in parallel mode selection and one of 100 channels in serial mode selection.
PARALLEL MODE
In parallel mode, the channel is selected via the inputs applied to PL1 pin 6 and PL1 pin 8. The channel select inputs are a binary representation of the channel number as shown in the table.
PIN 6 PIN 8 CHANNEL
HIGH HIGH 1
LOW HIGH 2
HIGH LOW 3
LOW LOW 4
SERIAL MODE
In serial mode the required channel is programmed using a serial input word (0 to 99 inclusive) at 9600 baud RS232 level applied via PL1 pin 8.
Mode selection is also achieved through the serial port. Transmission of character 160 (decimal) selects parallel mode/reset and transmission of character 161 (decimal) characters three times, (to avoid accidental selection), selects serial mode/reset.
Frequency assignment/channel numbering can be reprogrammed using the SPROG software (available separately).
Figure 3 Link Positions
OPERATING MODES
To provide maximum flexibility, a number of options are available via links (as detailed in the figure and table below) which allow users to configure the SR450 according to their own requirements.
PL3 PL4 PL5
pin 1 pin 2 pin 1 pin 2 pin 3 pin 4 pin 5 pin 1 pin 2 pin 3
Flat audio response LINK
Audio de-emphasis
(-6dB per octave) LINK
Data output DC-coupled
analogue output that bypasses squelch gate LINK LINK Disable mute (bypasses squelch gate) LINK
RANGE INFORMATION
The following table gives an indication of the typical ranges to be expected between a transmitter and receiver that have simple end-fed dipole antennas.
The following assumptions have been made in the calculations:
line-of-sight between antennas
0dB gain for the transmitter and receiver antennas
0dB loss for connectors and cables between the antenna and the radio connector
20dB fade and environmental margin
-100dBm received signal strength, allowing for digital and analogue signals
Range versus TX power
Frequency (MHz) Power (mW) Power (dBm) Range (km)
458.5 1mW 0 0.5
458.5 10mW 10 1.7
458.5 100mW 20 5.3
Wood and Douglas Ltd, Lattice House,
Baughurst Road, Tadley, Hampshire RG26 5LP 1892 1128 Tel: +44(0) 118 981 1444. Fax: +44(0) 118 981 1567 2.2/February 2000
TECHNICAL SPECIFICATION
Frequency range : 430 to 470MHz (contact Wood & Douglas for 350 to 500MHz operation)
Number of RF channels : 4 maximum using two bit parallel input
100 channels programmed using asynchronous serial input
Channel spacing : 12.5, 20kHz and 25kHz
Modulation type : F1D/F2D/F3D
Sensitivity : >-115dBm for 12dB SINAD (Flat audio response)
Image rejection : >70dB
Intermediate frequencies : 21.4MHz and 455kHz
Conducted spurious : <2nW (-57dBm) at any frequency Recovered audio level : 600mV p/p (+/-20%) into 10k ohms
Squelch type : Noise operated
Squelch status : open collector NPN 50mA max output (on under no signal condition)
RSSI option : output 0 to 3 volts (1kS) : dynamic range 50dB
Supply voltage : +6 to +15 volts DC
Supply current : 45mA
Size : 113 x 57 x 22mm (l x w x h)
Weight : 110g
Operating temperature : -10 to +55E C Storage temperature : -30 to +70E C
