rx1-173.200-10 Radiometrix Ltd, rx1-173.200-10 Datasheet - Page 7

• Manufacturer Part Number: rx1-173.200-10
• Description: Left Tx1 Transmitter Right Rx1receiver
• Manufacturer: Radiometrix Ltd

TX1 modulation requirements
The module is factory-set to produce the specified FM deviation with a TXD input to pin 7 of 3V
amplitude, i.e. 0V “low”, 3V “high”. Reducing the amplitude of the data input from this value (usually as
a result of reducing the supply voltage) reduces the transmitted FM deviation to typically 2.5kHz at
the lower extreme of 2.2V. The receiver will cope with this quite happily and no significant degradation
of link performance should be observed as a result.
Where the module supply is greater than 3V a resistor must be added in series with the TXD input to
limit the modulation amplitude to a maximum of 3V on pin 7. TXD input resistance is 100k
giving typical required resistor values as follows:
It should be noted that conditions on TXD have a significant effect on the startup time of the module,
i.e. the time between En (or En+Vcc) going high and full RF output being produced. For fastest startup
TXD should either be low or fed with data (preamble etc) for a minimum of 3ms after En has been
asserted. Startup time under these conditions is typically 50-70% of that obtained if TXD is held high
over the same period.
Reducing the output power of the TX1
If the TX1-173.250-10 is to be used for other than industrial/commercial applications its output power
must be reduced to 1mW to comply with type approval requirements. This is done by inserting a 10dB
attenuator network between the module and the antenna or feed, as follows:
Keep all tracking around the attenuator network as short as possible, particularly ground paths, and
use matched 50
1.6mm thick FR4 PCB).
Radiometrix Ltd., TX1 & RX1 Data Sheet
antenna
100R
68R
microstrip lines for input and output connections (track width of 2.5mm if using
1
2
3
schematic diagram
TX1
Fig.7: 10dB attenuator for TX1
3.3V
Vcc
5V
9V
3V
4
5
6
Series resistor
7
220k
10 k
68k
-
to antenna
Resistors are SMD (0603/0805)
physical arrangement
50 ohm microstrip lines
vias to ground plane
ground foil/
68R
from TX1
to ground,
page 7