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LMT2/LMR2
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The LMT2 transmitter and LMR2 receiver
modules offer a multi channel, low power, and reliable data
link. This makes the LMT2/LMR2 pair ideally suited to those
low power applications where existing wideband modules have
insufficient range, or where low cost multi-channel operation
is needed without compromising on RF specification or regulatory
requirement
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Figure 1: LMR2-433-5 and LMT2-433-5 |
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-
Conforms to
EN 300 220-3 and EN 301 489-3
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High performance
double superhet, PLL synthesizer with TCXO
- quasi-dc (peak sampling) data recovery
circuit (for enhanced performance on unbalanced datastreams)
- SAW front end filter
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Data rates up
to 5 kbps for standard module
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Usable range
over 500m
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Fully screened.
Low profile
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Feature-rich
interface (RSSI, analogue and digital baseband)
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Re-programmable
via RS232 interface
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Low power requirements
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Handheld terminals
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EPOS equipment,
barcode scanners
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Data loggers
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Industrial telemetry
and telecommand
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In-building
environmental monitoring and control
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High-end security
and fire alarms
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DGPS systems
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Vehicle data
up/download
- Heavy vehicle/machinery controls
Technical Summary
- Operating frequency: 433.875-434.65 0MHz
(EU band)
458.525
- 459.1MHz (UK band)
- Other custom UHF bands
- 32 channels
- Transmit power: +10dBm (10mW) / +20dBm
(100mW)
- Supply range: 3.1 - 15V (TX @ 10mW
and RX), 4.1 - 15V (TX @ 100mW)
- Current consumption: : 34mA @ 10mW,
90mA @ 100mW (transmit) and 20mA (receive)
- Data bit rate: 5kbps max. (standard
module)
- Receiver sensitivity -118dBm (for
12dB SINAD)
- Serial configuration by inverted RS232
at 3V CMOS level
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| Evaluation
Platform: Narrow
Band Evaluation Kit |
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Figure 2: LMT2 block diagram |
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Figure 3: LMT2 Footprint
(Top view)
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| Pin Description - LMT2 |
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Pin
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Name
|
Function
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1a
|
Vcc |
3.1 - 15V power
supply (@ 10mW)
4.1 - 15V power supply (@ 100mW) |
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2a
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0V |
Ground |
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3a
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TXE |
Transmit Enable (active low) |
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4a
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TXD |
DC coupled input for 3V CMOS
logic. Rin=47kW |
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5a
|
No pin |
Not present in LMT2 |
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1b
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P0/PGM
|
Parallel Channel select LSBSerial frequency
programming / configuration1 |
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2b
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P1 |
Parallel Channel select |
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3b
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P2 |
Parallel Channel select |
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4b
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P3 |
Parallel Channel select MSB |
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5b
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No pin |
Not present in LMT2 |
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NOTES:
1. Serial programming is by an inverted, CMOS logic level,
2400 baud RS232 datastream applied to the P0 pin.
2. Channel select inputs have pullups (50K) to 3v internal
rail. Do not exceed 3V logic levels on this port.
3. Channel select inputs are active low
4. TXE has a 100K pullup to Vcc
5. All pins are on an 0.1" grid
6. The pins 5a/b are not present, but are included in footprint
for compatibility with other units in this family
7. In the 'off' state a PIN switch open circuits the RF
output pin. There are no 'off' state spuri.
8. 10mW unit will operate (with marginally reduced specifications
and lower (6-8mW) output power) from a 3.0V rail. This must
be well regulated and without noise or ripple, as in this
state the unit's internal regulator no longer operates,
and provides no supply rejection.
9. 100mW versions should not be run continuously from supply
voltages > 9v
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Figure 4: LMR2 block diagram
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Figure 5: LMR2 Footprint
(Top view)
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| Pin Description
- LMR2 |
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Pin
|
Name
|
Function
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| 1a |
Vcc |
3.1 - 15V power supply |
| 2a |
0V |
Ground |
| 3a |
RXE |
Receiver Enable (active high) |
| 4a |
RXD |
Data out (open collector,
no pullup) |
| 5a |
AF out |
700mV p-p audio. DC coupled,
approx 0.8v bias. |
| 1b |
P0/PGM
|
Parallel Channel select LSBSerial
frequency programming / configuration1 |
| 2b |
P1 |
Parallel Channel select |
| 3b |
P2 |
Parallel Channel select |
| 4b |
P3 |
Parallel Channel select MSB |
| 5b |
RSSI |
DC level between
0.5v and 2.2v. 60dB dynamic range |
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NOTES:
1. Serial programming is by an inverted, cmos
logic level, 2400 baud RS232 datastream applied to the P0 pin.
2. Channel select inputs have pullups (50kW)
to 3v internal rail. Do not exceed 3v logic levels on this port.
3. Channel select inputs are active low
4. All pins are on an 0.1" grid
5. Data recovery circuit used for RXD is not a simple 'average
and compare' type. It is a peak sampling quasi-DC coupled design,
allowing a greater than usual flexibility in data format.
6. Unit will operate (with maginally reduced specifications) from
a 3.0v rail. This must be well regulated and without noise or
ripple, as in this state the unit's internal regulator no longer
operates, and provides no supply rejection.]
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Serial interface commands
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| LMT2/LMR2 frequency/channel
can be serially configured using HyperTerminal or any other terminal
program configured with following setup: |
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| 2400 baud RS232, 8
bit data, no parity, 1 start bit, 1 or 2 stop bits. No flow control |
| Serial data is sent
to the unit on one of the parallel channel select pins (P0). It
is very important that the unit does not 'decode' switch bounce
in ordinary operation as a command string, or spurious re-writing
of the EEPROM will result. For this reason the user must send the
16 character string ENABLESERIALMODE to fully enable the serial
command mode before sending any of the command strings listed below.
Command mode is disabled on power down, or on reception of a # character.
To successfully program the unit, it must be enabled (RXE high (rx)
or TXE low (tx)). |
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| GOCHAN aa |
Serial select
of channel aa (0 to 31) |
| LOAD aa nnnnn |
Set value of N register for
channel aa, where aa is Channels 0 to 31 |
| RVALUE rrrr |
Set value for R register |
| SETPAR |
Channel selected
by 4 bit parallel inputs (ch0 to ch15 only) |
| SETSER |
Channel selected by most recent
'GOCHAN' operation |
| SINGLE nnnnn |
Set value of N
for single channel operation.
N value NOT stored in EEPROM |
| <cr> |
Process entry |
| / |
Clear all buffers |
| # |
Disable command mode |
aa = a two digit channel number from 00 to
31
nnnnn = a synthesizer N register value, (up to 65535)
rrrr = the synthesizer R register value, (up to 16383)
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So R = 520 |
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Notes:
A pause of at least 50ms must be allowed between command strings
(EEPROM programming time).
SINGLE mode does not store the N value in EEPROM. Therefore the
unit is inoperative after a power down until either another valid
SINGLE command is received, or mode is changed by a GOCHAN, SETPAR
or SETSER command. SINGLE mode is intended for frequency agile
applications.
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| LMT2, LMR2 channels are spaced
at 50kHz interval into two frequency groups. 50kHz spacing between
sequential channels minimises adjacent channel interference.
e.g. 433MHz band
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Serial
or Parallel channel select
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Frequency (MHz)
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Serial channel select
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Frequency (MHz)
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16
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433.875 |
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0 (P3:P0 = HHHH)*
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433.900 |
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17
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433.925 |
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1
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433.950 |
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18
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433.975 |
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2
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434.000 |
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19
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434.025 |
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3
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434.050 |
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20
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434.075 |
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4
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434.100 |
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21
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434.125 |
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5
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434.150 |
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22
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434.175 |
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6
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434.200 |
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23
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434.225 |
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7
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434.250 |
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24
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434.275 |
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8
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434.300 |
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25
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434.325 |
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9
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434.350 |
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26
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434.375 |
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10
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434.400 |
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27
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434.425 |
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11
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434.450 |
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28
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434.475 |
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12
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434.500 |
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29
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434.525 |
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13
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434.550 |
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30
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434.575 |
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14
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434.600 |
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31
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434.625 |
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15 (P3:P0=LLLL)*
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434.650 |
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NOTE: Parallel select pins: H=3V,
L= 0V |
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Condensed specifications
| Frequency |
433MHz EU band,
and 458MHz UK band
As supplied: EU version: 433.875 - 434.65MHz (25kHz steps)
UK version 458.525 - 459.1MHz (25kHz steps)
Other custom UHF bands |
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Frequency
stability
|
+/- 1.5kHz |
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Channel
spacing
|
25kHz |
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Number
of channels
|
16 channels controlled by parallel port or 32 via RS232
interface
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| Operating temperature |
-10 to +60 °C (Storage
-30 to +70 °C) |
| Spurious radiations |
Compliant with ETSI EN 300
220-3 and EN 301 489-3 |
| Intended approval |
ETSI EN 300 220-3 (radio)
and EN 301 489-3 (EMC) |
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| LMT2 Transmitter
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| Supply |
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| Voltage |
3.1V - 15V (1-25mW)
4.1 - 15V (25 - 100mW) |
| Current |
34mA @ 10mW (nominal)
65mA @ 50mW (nominal)
90mA @ 100mW (nominal)
<5mA standby (TXE high or floating) |
| Output power |
10mW +/- 1dB |
| TX on switching
time |
50ms from power
up |
| Peak FM deviation |
+/-3kHz |
| Modulation type |
FSK (F3D) |
| TX modulation
bandwidth |
DC - 5kHz (3V
CMOS compatible) |
| Adjacent channel TX power |
-37dBm |
| TX spurious |
<-45dBm (no RF output
in Standby) |
| Inputs |
data (CMOS/TTL compatible) |
| Size |
33 x 23 x 9mm |
| User |
10 (8) pin 0.1" pitch
dual row (5+5) header |
| RF |
2pin .1" pitch |
| Recommended
PCB hole size |
1.2mm |
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| LMR2 Receiver |
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| Sensitivity |
-118dBm for
12 dB SINAD |
| S/N ratio |
35dB (min),
40dB (typ) on AF output |
| AF bandwidth
(-3dB) |
4kHz |
| image |
< -60dB |
| other spurious |
<-70dBm |
| blocking |
better than 84dB |
| LO re-radiation |
-70dBm |
| adj. Channel |
better than -60dB (Tested
per. ETSI EN 301 489-3) |
| Supply |
|
| Voltage |
3.1V - 15V |
| Current |
20mA; <1mA
standby (RXE low) |
| outputs |
RSSI, audio,
digital data (quasi DC data recovery circuit) |
| Size |
46 x 23 x 9 mm |
| Interface |
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| User |
10 pin 0.1" pitch dual
row (5+5) header |
| RF |
2pin 0.1" pitch molex |
| Recommended
PCB hole size |
1.2mm |
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| Dynamic timing |
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| RXE high/active
to RX AF stable |
25ms |
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RXE high/active RX data stable
|
40ms |
| RX data recovery
settling time |
20ms |
| Power on to
stable (50:50 mark / space) RXD |
50ms
(TXE low/active to stable
RX data out) |
| Maximum time
between data transitions |
250ms |
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RX Received Signal Strength Indicator (RSSI)
The LMR2 has wide range RSSI which measures the strength of an
incoming signal over a range of 60dB or more. This allows assessment
of link quality and available margin and is useful when performing
range tests.
The output on pin 5b of the module has a standing DC bias of
up to 0.5V with no signal, rising to 2.5V at maximum indication
(RF input levels of -40dBm and above). DVmin-max
is typically 2V and is largely independent of standing bias variations.
Output impedance is 40kW. Pin 5b can
drive a 100mA meter directly, for simple
monitoring.
Typical RSSI characteristic is as shown below:
Figure 6: RSSI level with respect to received RF level at LMR2
antenna pin
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| Antenna
requirements
Three types of integral antenna are recommended
and approved for use with the module:
A) Whip: This
is a wire, rod, PCB track or combination connected directly to
RF pin of the module. Optimum total length is 16cm (1/4 wave @
433MHz). Keep the open circuit (hot) end well away from metal
components to prevent serious de-tuning. Whips are ground plane
sensitive and will benefit from internal 1/4 wave earthed radial(s)
if the product is small and plastic cased
B) Helical:
Wire coil, connected directly to RF pin, open circuit at other
end. This antenna is very efficient given it's small size (20mm
x 4mm dia.). The helical is a high Q antenna, trim the wire length
or expand the coil for optimum results. The helical de-tunes badly
with proximity to other conductive objects.
C) Loop:
A loop of PCB track tuned by a fixed or variable capacitor to
ground at the 'hot' end and fed from RF pin at a point 20% from
the ground end. Loops have high immunity to proximity de-tuning.
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A
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B
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C
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Whip
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Helical
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Loop
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| Ultimate performance |
***
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**
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*
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| Easy of design set-up |
***
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**
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*
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| Size |
*
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***
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**
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| Immunity proximity effects |
*
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**
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***
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| Range open ground to similar
antenna |
500
|
200
|
100
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| The antenna
choice and position directly controls the system range. Keep it
clear of other metal in the system, particularly the 'hot' end.
The best position by far, is sticking out the top of the product.
This is often not desirable for practical/ergonomic reasons thus
a compromise may need to be reached. If an internal antenna must
be used, try to keep it away from other metal components, particularly
large ones like transformers, batteries and PCB tracks/earth plane.
The space around the antenna is as important as the antenna itself. |
Figure 7: Antenna types
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| Ordering
Information |
| Part No. |
Description |
Frequency
band (MHz) |
| LMT2-433-5 |
UHF multi channel narrow band
FM transmitter |
433.900- 434.650 |
| LMR2-433-5 |
UHF multi channel narrow band
FM receiver |
433.900 - 434.650 |
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| LMT2-458-5 |
UHF multi channel narrow band
FM transmitter |
458.525 - 459.1 |
| LMR2-458-5 |
UHF multi channel narrow band
FM receiver |
458.525 - 459.1 |
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Limitation of liability
The information furnished by Radiometrix
Ltd is believed to be accurate and reliable. Radiometrix Ltd
reserves the right to make changes or improvements in the design,
specification or manufacture of its subassembly products without
notice. Radiometrix Ltd does not assume any liability arising
from the application or use of any product or circuit described
herein, nor for any infringements of patents or other rights
of third parties which may result from the use of its products.
This data sheet neither states nor implies warranty of any kind,
including fitness for any particular application. These radio
devices may be subject to radio interference and may not function
as intended if interference is present. We do NOT recommend
their use for life critical applications.
The Intrastat commodity code for all our modules is: 8542 6000.
R&TTE Directive
After 7 April 2001 the manufacturer can only
place finished product on the market under the provisions of
the R&TTE Directive. Equipment within the scope of the R&TTE
Directive may demonstrate compliance to the essential requirements
specified in Article 3 of the Directive, as appropriate to the
particular equipment.
Further details are available on The Office of Communications
(Ofcom) web site:
Licensing
policy manual
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