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BHX2
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The BHX2 transceiver module offers a
500mW RF power output in the UK 458MHz band. This makes
the BHX2 ideally suited to those low power applications
where existing multi-channel narrow band devices like
TR2M have insufficient range.
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Figure 1: BHX2-458-5-MCx
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Features
-
Conforms
to EN 300 220-3 and EN 301 489-3
- Any 5MHz band module from 420MHz
to 480MHz available as factory tuned custom variant
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High
performance double superhet, 128 channel PLL synthesizer
with TCXO
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Data
rates up to 5 kbps for standard module
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Usable
range over 5km
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Fully
screened
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Feature-rich
interface (RSSI, noise squelch, analogue and digital
baseband)
- Incorporates a 1200baud dumb
modem
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Re-programmable
via RS232 interface
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Low
power requirements
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Handheld
terminals
- Heavy vehicle/machine remote controls
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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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Vehicle
data up/download
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Technical
Summary
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Operating frequency:
458.5-459.1MHz
- Custom variants from 420MHz to
480MHz on any 5MHz band
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23 channels
in 458MHz band (128 channels max.)
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Transmit power:
+27dBm (500mW) nominal
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Current consumption:
350mA transmit, 30mA receive
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Data bit rate:
5kbps max. (standard module)
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Receiver sensitivity:
-118dBm (for 12 dB SINAD)
- Size: 85 x 39 x 13 mm (RF pin
version)
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| Evaluation Platform:
Narrow
Band Evaluation Kit |
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Figure2: BHX2 block diagram |
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Figure 3: BHX2 Footprint (Top)
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| User Interface |
| 1 |
TXE |
Transmitter
enable. Low = ON, open = RX mode. Internal 10kW
pullup to 4V |
| 2 |
TXD |
DC coupled digital data
input for 3-12V CMOS logic. Leave open if unused |
| 3 |
AF in |
50mV - 2.5v p-p AC coupled
input. Variable gain |
| 4 |
RSSI |
DC level between 0.5V
and 2.5V. 60dB dynamic range |
| 5 |
SQF |
Noise operated carrier
detect. Open collector. ON/low = no signal |
| 6 |
AF out |
200mVpk-pk audio. DC coupled,
approx 1V bias. Muted by squelch |
| 7 |
RXD |
Open collector output
of data slicer suitable for biphase codes |
| 8 |
+4.4Vout |
Regulated DC supply. 75mA
max. drain. Present if unit is powered |
| 9 |
0V |
Ground |
| 10 |
PGM |
Serial programming/control
input at true RS232 level |
| 11 |
P1 |
Parallel
frequency select inputs. Inverted logic, 10k pullups to
4V |
| 12 |
P2 |
| 13 |
P3 |
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Notes:
1. BHX2 transmitter section inverts
sense of the baseband stream, so a logical inversion is present
between input of TX and output on RX
2. Carrier detect mutes the AF and DATA outputs. It can be disabled
by rotating the level set trimmer fully ACW.
3. There are no pullups on the open collector outputs.
4. The sofware incorporates a 1200baud dumb modem, compatible
with that implemented in TX2M, RX2M, TR2M, SMX2 and UHX2 radios
( i1200 tones and format ).
5. RS232 input pins (10 and 11) tolerate true +/- levels. No
buffering is required.
6. This unit actually consists of a TR2C RF board and an AFS2-458
amplifier module, combined with a 5v LDO
7. In future versions of the software, pin 13 will have a modem
handshake function
8. The BHX2 has the same footprint/pinout/function as the TR2M
(TR2B), but the case is longer, and the RF output is a coaxial
connector. Compared to an TR2M, the minimum supply voltage is
higher (5.5v vesus 4.5v). |
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Figure 4: BHX2 interfaced to host
microcontroller and serial port for configuration
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| BHX2 can be directly
interfaced to a host microcontroller which can generally be
powered by the regulated +4.4V output on pin 8 of BHX2. Three
I/O pins on the microcontroller port can be assigned to select
the first 8 channels on frequency table of the appropriate band
for which the module is configured by pulling the P1-P3 pins
low. Channel select pins of BHX2 have internal pull-up to 4V
supply rail, hence channel selection operate on inverted logic. |
| Channel |
P3:P2:P1 |
458MHz
band |
| 0 |
111 |
458.525 |
| 1 |
110 |
458.550 |
| 2 |
101 |
458.575 |
| 3 |
100 |
458.600 |
| 4 |
011 |
458.625 |
| 5 |
010 |
458.650 |
| 6 |
001 |
458.675 |
| 7 |
000 |
458.700 |
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| Digital
Received Data Output (RXD) pin is an open collector output,
which should be pulled-up to required voltage swing level (e.g.
+4.4V or Vcc).
BHX2 has an automatic noise squelching
function which is activated when there is not any RF signal
at detectable level on the channel or if the non-coherent
noise like interference level is high enough to block any
weak RF signal from being received. SQF is provided as an
open-collector output for monitoring which should be pulled-up
to required voltage swing level. SQF output will jump to pull-up
voltage level if received RF signal level at the RF In/Out
pin of the module is about 3dB below the level required to
produce 12dB SINAD level on demodulated AF Output signal.
SQF pin can be connected to an LED to act as a Carrier Detect
indicator. Pull-up resistor value should be reduced (e.g.
1kW) according to the current requirement to produce satisfactory
brightness on the LED used.
BHX2 can be configured using any PC/Laptop/PDA
having a serial port and modem/terminal program. TXD (pin
3) of DB9M connector can be directly wired to PGM (pin C10)
of the BHX2 and SGN (pin 5) of DB9M connector should be either
connected to common ground or pin C9 of the BHX2.
The whole frequency/channel table is user
reconfigurable to 128 channels within 5MHz band of supplied
frequency subject to regulatory band limits. Serial Channel
Selection via PGM pin gives access to the whole of regulatory
band allocation for 458.525MHz-458.925MHz (23 channels).
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Received Signal Strength
Figure
5: RSSI voltage variation with respect to RF level at BHX2
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| If the microcontroller
has a built-in Analogue to Digital Converter (ADC), the Received
Signal Strength Indicator (RSSI) output voltage level can be
read by the microcontroller to estimate its distance from transmitting
BHX2 unit or identify areas of weak signal reception.
RSSI can also be used to make a decision
to switch to the second antenna in fixed installations within
building where the probability of null-spots are higher.
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BHX2 serial interface
commands
2400 baud RS232. 8 bit data, no parity,
1 start bit, 1 or 2 stop bits, No flow control
| SINGLE nnnnn |
set value of N for single
channel operation |
| GOCHAN xx
|
serial select
of channel xx (0 to 127) |
| LOADMX xx |
set highest permitted
(serial selected) channel xx (others default to ch0) |
| LOAD aa nnnnn |
set value of N for channel
aa (channels 0 to 15) |
| LOADTB nnnnn |
set value of
N for channel 16 (channels 17 to 127 then in sequence) |
| RVALUE rrrr |
enter value for R register |
| SETPAR |
channel selected by 3
bit parallel input (0 to 7). Disable modem |
| SETSER |
channel selected by most
recent 'gochan' operation |
| SETMOD |
enable internal modem.
Frequency selected by most recent 'gochan' or 'single' |
| GOTEST |
250Hz test tone transmission |
| OFFSET ooo |
Set receive frequency
offset (for 25KHz this is 1800) |
| <cr> |
process entry |
| / |
clear all buffers |
xx = a channel number from 00 to 127
aa = a two digit channel number from 00 to 15
nnnnn = a synthesizer N register value, (up to 65535)
rrrr = the synthesizer R register value, (up to 16383)
000 = frequency offset
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, So R = 520 |
| RX OFFSET = IF/Channel
spcacing |
45MHz /25kHz = 1800 |
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| Notes: |
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1.
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.
2. /SETPAR command should be issued at the end of channel
programming to put the module back into parallel frequency
select mode
3. In 458MHz band, channel 12 (458.825MHz) and channel 15
(458.900MHz) are allocated specifically for fixed alarm and
radio keys/vehicle paging applications respectively and should
not be used for general purpose applications.
4. User can
modify the frequency table of 128 channels to any desired
frequency by changing N, R values of synthesizer within ±2.5MHz
of factory set Channel 0 frequency subject to the Radio Regulatory
Band Allocation in the country of intended use.
5. All other
frequency, power, analogue input gain and automatic noise
squelching adjustment will be treated as custom variants of
the module to be set by factory.
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Pin description
of BHX2 with Modem mode selected
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| The 'modem' mentioned
is a 1200 baud RS232 semi-intelligent unit (Transmit keyed when
valid serial data is present, so no separate TX control needed.
Coding in the datastream also permits the receiver to ignore
noise and only output valid serial data). This is a half duplex
unit, so collisions between transmitted and received packets
must be dealt with by the user. |
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Pin Description
- BHX2
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Pin
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Name
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Function
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| 1 |
MOD TX_ON |
Open = normal modem operation.
Low = constant TX (for test) 10k pullup to 4V |
| 2 |
MOD NC |
Leave open |
| 3 |
MOD NC |
Leave open |
| 4 |
RSSI |
DC level between 0.5V and 2.5V.
60dB dynamic range (only valid during databursts) |
| 5 |
MOD NC |
Leave open |
| 6 |
AF out |
Modem tones or noise present |
| 7 |
n/c |
Leave open |
| 8 |
+4.4Vout |
Regulated DC supply. 75mA max.
drain. Present when unit is powered |
| 9 |
0V |
Ground |
| 10 |
PGM |
Serial programming/control input
at RS232 level |
| 11 |
MOD TXD |
RS232 data input (true). 10k
pullup to 4V |
| 12 |
MOD RXD |
Inverted "RS232" data
out (to inverting buffer like MAX232) |
| 13 |
MOD NC |
Leave open |
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| BHX2s on both
ends should be configured to required operating frequency using
GOCHAN command before starting to use the internal 1200 baud
modem, because the P1-P3 pins will be used as Modem Data pins
and the modem will operate on the last serially selected channel
after SETMOD command is used to enable the Modem. |
Figure
8: BHX2 interfaced to PC serial port in modem mode
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Note:
Baud rate used for Modem is half that of used for serial
configuration. Attached RS232 devices should be set with
the following:
1200bps,
8 Data bits, No Parity, 1/2 stop bits, no flow control
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| TXD (Pin 3) of
a Serial Port can be switched from PGM (Pin C10) to MOD TXD
(Pin C11) with no RS232 driver in between. However, MOD RXD
(Pin C12) requires an RS232 line driver before it can be connected
to RXD (pin 2) of a serial port. Some of the RS232 line drivers
can be powered from the regulated +4.4V out (Pin C8). |
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| Condensed
specifications |
| Frequency |
458.5-459.1MHz
(any 5MHz band from 420-480MHz)and any 3MHz band from
210 - 270MHz) |
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Frequency
stability
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+/-
1.5kHz |
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Channel
spacing
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25kHz
(12.5kHz by special order) |
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Number
of channels
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128
channels controlled via RS232 interface (8 parallel selected) |
| Supply
voltage |
5.5V
- 15V (+5V regulated version available) |
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Current |
350mA
nominal transmit |
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30mA
receive |
| Operating
temperature |
-20
to +60 °C (Storage -30 to +70 °C) |
| Size |
85 x 39 x 13 mm Case only
(RF pins version)
92 x 39 x 13mm (including MCX)
105 x 39 x 13mm (including SMA) |
| Spurious
radiations |
Compliant
with ETSI EN 300 220-3 and EN 301 489-3 |
| Interface
user |
13pin
0.1" pitch molex |
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Power
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2pin
0.1" pitch molex |
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RF
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3pin
0.1" pitch molex
or SMA (long, bulkhead mounted type) or MCX |
| Recommended
PCB hole size |
1.2mm |
| Intended
approval |
ETSI
radio standard EN 300 220-3 and EMC standard EN 301 489-3 |
| Transmitter
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| Output
power |
+27dBm (500mW) ±1dB |
| TX
on switching time |
50
ms |
| Modulation
type |
FM,
FSK (F1D, F3D) |
| TX
modulation bandwidth |
DC
- 3kHz |
| Adjacent
channel TX power |
<-37dBm
(<200nW) |
| Inputs |
analogue,
data (CMOS/TTL compatible) |
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| Receiver
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| Sensitivity |
-118dBm
for 12 dB SINAD |
| image / spurious |
-70dB |
| adjacent
Channel |
<-65dB (Tested per.
ETSI EN 301 489-3) |
| blocking |
-85 |
| outputs |
RSSI,
carrier detect, audio, data |
| Power
on to valid audio (no noise mute) |
28ms |
| Power
on to valid audio (with noise mute ) |
45ms |
| Power
on to stable data out (50:50 mark / space) |
50ms
(with or without mute) |
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| Notes: |
1. |
The data
slicer cannot be depended upon for data waveform frequencies
below 250Hz |
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2. |
When RX
is on and a transmitter keys up, again a 50ms period
is required to stabilise data output mark/space. i.e.
allow at least 50ms of preamble |
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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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