RFDesign RFD900ux Instructions for use

www.rfdesign.com.au
RFD900ux Radio Modem Series
Hardware User Manual
902-928MHz frequency band

RFD900ux Data Sheet
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1
Last update 12/09/2019
General Cautions
During operation there must be a separation distance of 20cm between all persons and the antenna.
Ensure that all used RF connectors are secure and properly terminated.
When used in the US - FCC Caution
Caution: The user is cautioned that changes or modifications not expressly approved by the party responsible for
compliance could void the user's authority to operate the equipment.
Note: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15
of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential
installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful interference to radio communications. However, there is no
guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by turning
the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following
measures:
—Reorient or relocate the receiving antenna.
—Increase the separation between the equipment and receiver.
—Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
—Consult the dealer or an experienced radio/TV technician for help.
This equipment complies with FCC’s RF radiation exposure limits set forth for an uncontrolled environment. The antenna(s)
used for this transmitter must be installed and operated to provide a separation distance of at least 20 cm from all persons
and must not be collocated or operating in conjunction with any other antenna or transmitter. Installers must ensure that
20cm separation distance will be maintained between the device (excluding its handset) and users.
When used in Canada - ISED Caution
This device complies with RSS 210 of the Industry Canada Rules. Operation is subject to the following two conditions:
(1) this device may not cause interference, and (2) this device must accept any interference, including interference that may
cause undesired operation of the device.
Le présent appareil est conforme aux CNR d’Industrie Canada applicables aux appareils radio exempts de licence.
L’exploitation est autorisée aux deux conditions suivantes :
(1) l’appareil ne doit pas produire de brouillage, et (2) l’utilisateur de l’appareil doit accepter tout brouillage
radioélectrique subi, même si le brouillage est susceptible d’en compromettre le fonctionnement.
This equipment complies with Canada radiation exposure limits set forth for uncontrolled environments. This equipment
should be installed and operated with a minimum distance of 20cm （may be adjusted according to actual calculation
result）between the radiator and your body.
This transmitter must not be co-located or operating in conjunction with any other antenna or transmitter.
Déclaration d’IC sur l’exposition aux radiations:
Cet équipement est conforme aux limites d’exposition aux radiations définies par le Canada pour des environnements non
contrôlés. Cet équipement doit être installé et utilisé à une distance minimum de 20 cm entre l’antenne et votre corps.
Cet émetteur ne doit pas être installé au même endroit ni utilisé avec une autre antenne ou un autre émetteur
Acceptable Antennas
This device has been designed to operate with the antenna(s) listed below and having a maximum gain of 3 dBi. Antennas not
included in this list or having a gain greater than 3 dBi are strictly prohibited for use with this device. The required antenna
impedance is 50 ohms.
Acceptable antenna – 3dBi RFD whip.

RFD900ux Data Sheet
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Last update 12/09/2019
Table of contents
1 Key features ....................................................................................................................................3
2 Specifications ..................................................................................................................................4
3 OEM Labelling .................................................................................................................................5
4 Output power levels........................................................................................................................6
5 Performance characteristics ...........................................................................................................7
6 Pin signals and layout......................................................................................................................9
7 Recommended PCB Design...........................................................................................................11
8 Physical dimensions......................................................................................................................12
9 Diversity ........................................................................................................................................13
9.1 Spatial diversity.....................................................................................................................13
9.2 Polarisation diversity.............................................................................................................13
10 PCB Design Guidelines ..............................................................................................................14
11 Useful links................................................................................................................................15
12 Document revision history........................................................................................................16

RFD900ux Data Sheet
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Last update 12/09/2019
1Key features
RFD900ux provides compact and yet powerful data communication. The key features are:
•No configuration required for out of the box RF communications.
•Operating frequency range of 902 –928MHz
•Outdoor RF line-of-site range of 40km or more depending on antennas
•Air data rate speeds of up to 224kbps
•Diversity antenna support
•Operating temperature of -40 to +85 degrees Celsius
•Dimensions of 21mm x 29mm x 4.2mm
•Weight of 3.5g
•USB interface
Compliances and Worldwide Acceptances:
The RFD900ux is designed to be compliant to AS4268:2012, and FCC 15.247. It has not been certified
as a standalone modem and should be compliance tested in the final product.

RFD900ux Data Sheet
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2Specifications
Performance
Supported RF Data Rates
12, 56, 64, 100, 125, 200, 224, 5001and 750kbps1
Indoor Range
500m –1km
Line-Of-Sight Range
40km or more depending on antennas
Transmit Power
0 to 30dBm in 1dBm steps
Receiver Sensitivity
113dBm @ 10-5 BER 12Kbps
1 High RF data rates are for experimental purposes only
Features
Serial Data Interface
+3.3V nominal, 3.3V tolerant
Configuration Method
AT Commands, APM Planner, Customised Configuration Tool
Frequency Band
Unlocked
902MHz - 928MHz
AU locked
915MHz - 921MHz
NZ locked
920.75MHz –927.25MHz
US locked
902MHz - 915MHz
Interference Immunity
FHSS (Frequency Hopping Spread Spectrum)
Serial Interface Data Rate
2400, 4800, 9600, 19200, 38400, 57600, 115200, 460kbps
Antenna Connection
2 x RPSMA diversity switched ports
GPIO
6 pins (Digital, PPM capable)
Compliance Standards
FCC Part 15.247, AS/NZS 4268:2012
Networking and Security
Addressing Options
Network ID: 0 –255
Channels
Unlocked
Up to 50 Frequency Hopping Channels
AU locked
23
NZ locked
25
US locked
51
Supported Network Topologies
Point-to-point, multipoint2, and asynchronous non-hopping
mesh2
2 Only available in separate firmware versions available in the website
Power Requirements
Supply Voltage
+5V nominal (+5V min, +5.5V Max, +6V ABS Max),
Transmit Current
~1A peak at max power
Receive Current
~60mA

RFD900ux Data Sheet
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3OEM Labelling
For equipment containing the RFD-900x where the RFD-900x label is not visible the following applies.
Equipment using the RFD 900x in the USA must display a label referring to the enclosed module. This
label must contain the words “Contains FCC ID: 2ADLE-900X”.
Equipment using the RFD 900x in Canada must display a label referring to the enclosed module. This
label must contain the words “Contains IC ID: 24610-900X”.

RFD900ux Data Sheet
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Last update 12/09/2019
4Output power levels
Many countries have different legal power levels. Be sure to operate within the legal power limits of
the country that you are operating in. The RFD900ux modem can support the power levels between
0dBm and 30dBm in 1dBm steps. Formula 2-1 can be used to convert the power in dBm into milliwatts.
 󰇛 
󰇜
Formula 2-1
To calculate Effective Isotropic Radiated Power (EIRP) you can use the formula 2-2 below:
󰇛󰇜 󰇛󰇜 󰇛󰇜󰇛󰇜
Formula 2-2
The FCC limit for EIRP is 4 Watts, or 36dBm for frequency hopping radios in the ISM 900 MHz band.
The Australian EIRP limit is 30dBm as defined by ACMA.

RFD900ux Data Sheet
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5Performance characteristics
Figure 4-1 shows how the output power of the RFD900ux varies with supply voltage when the output
power is set to +30dBm.
Figure 4-1: Output power vs. input supply voltage
Figure 4-2 shows how the current through the RFD900ux varies with the transmit power level. The
current during transmission is shown by the ‘High Level’ plot and that during receive mode is shown
by the ‘Low Level’ plot.
Figure 4-1: Current consumption vs. TX power level
28
28.2
28.4
28.6
28.8
29
29.2
29.4
29.6
3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5
Power Output (dBm)
Supply Voltage (Vcc)
0
100
200
300
400
500
600
700
800
900
0 5 10 15 20 25 30 35
Peak Current (mA)
Power Level (dBm)

RFD900ux Data Sheet
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The table below is used to determine the sensitivity of the RFD900ux according to the selected air
data rate. The link budget is directly affected by the sensitivity, and therefore the communication
range also varies. The sensitivity values in the table are based on a 10-5 BER.
Air data rate
Sensitivity @ 10-5 BER
12 kbps
-111 dBm
64 kbps
-104 dBm
125 kbps
-102 dBm
224 kbps
-95 dBm
12 kbps
-111 dBm

RFD900ux Data Sheet
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Last update 12/09/2019
6Pin signals and layout
Figure 5-1: Physical pin layout of the RFD900ux Radio Modem
Pin #
Name
Direction
Description
Max Voltage
1
VUSB
Input
Power supply from USB
5V
2
USB_DM
USB Data -
3
USB_DP
USB Data +
4
SWO_EXT
Output
SWD debug output
3.3V
5
P3.3_EXT
I/O
Digital I/O
3.3V
6
P3.4_EXT
I/O
Digital I/O
3.3V
7
P3.5_EXT
I/O
Digital I/O
3.3V
8
GND
-
Ground
0V
9
GND
-
Ground
0V
10
+3V3
LDO output
3.3V
11
GND
-
Ground
0V
12
GND
-
Ground
0V
13
ANT1
-
Antenna 1
-
14
GND
-
Ground
0V
15
GND
-
Ground
0V
16
ANT2
-
Antenna 2
-
17
GND
-
Ground
0V
18
GND
-
Ground
0V
19
+5V
Power Supply
5V
20
GND
-
Ground
0V
21
P1.0_EXT
I/O
Digital I/O
3.3V
22
P1.1_EXT
I/O
Digital I/O, PPM I/O
3.3V
23
P1.2_EXT
I/O
Digital I/O
3.3V
24
P1.3_EXT
I/O
Digital I/O
3.3V

RFD900ux Data Sheet
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25
SIRX_EXT
Input
UART Data In
3.3V
26
SITX_EXT
Output
UART Data Out
3.3V
27
SIRTS_EXT
Output
Request to send
3.3V
28
SICTS_EXT
Input
UART Clear to send
3.3V
29
GND
-
Ground
0V
30
GND
-
Ground
0V
In case there is a need to force the modem into boot mode, pull the SWO pin to the ground while
applying power. The on-board LED will become solid red when in bootloader mode.

RFD900ux Data Sheet
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7Recommended PCB Design
Symbol
Dimension (mm)
Symbol
Dimension (mm)
A
2
F
11.5
B
2.4
G
3.5
C
1
H
1.5
D
8
J
1.5
D1
7
K
21.2
E
6.6
L
0.5
E1
6

RFD900ux Data Sheet
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8Physical dimensions

RFD900ux Data Sheet
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9Diversity
The RFD900ux has two antenna ports and firmware which supports diversity operation of antennas.
During the receive sequence the modem will check both antennas and select the antenna with the
best receive signal. The antenna selected during receive is then also used for subsequent transmission.
In the case of only one antenna connected, it will automatically select the port with the antenna
connected. Testing by Silicon Labs has shown that link budgets can be improved up to the order of
8dB by employing a diversity scheme.
9.1 Spatial diversity
Spatial diversity is the case where the antennas are separated by some distance from one another. It
is recommended that two antennas connected to the RDF900ux modem be separated by at least
25cm, more if possible.
9.2 Polarisation diversity
Polarisation diversity is the case where the antennas are perpendicular to each other. i.e. one vertical,
and one horizontal. This is effective in reducing multipath effects which affect one or the other
polarisation. This scheme also helps to maintain the link between non-static objects such as aircraft
performing acrobatics by increasing the likelihood that one antenna will maintain the same
polarisation as an antenna on the other side of the link.

RFD900ux Data Sheet
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Last update 12/09/2019
10 PCB Design Guidelines
Some guidelines must be followed as to ensure the PCB design meets the RFD900ux thermal
dissipation and electromagnetic compatibility requirements. The proposed layout can be used as a
starting point and it is not guaranteed to comply with EM immunity and emissions regulations as is.
The PCB designer is expected to calculate the RF antenna track widths to be 50Ωoutputs, depending
on the host PCB layer stack up and dielectric constant.

RFD900ux Data Sheet
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11 Useful links
RFD900ux Firmware
The RFD900x runs the same firmware as all other radios from the RFD900x family.
http://files.rfdesign.com.au/firmware/
RFD SiK firmware is standard SiK (open source)
RFD Multipoint firmware is multipoint SiK (MP SiK)
RFD900x Flash Programmer
http://files.rfdesign.com.au/tools/
FTDI Cable documentation
http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf

RFD900ux Data Sheet
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12 Document revision history
Version
Date
Changes
1.0
20/08/2019
Release document
1.1
12/09/2019
Amended VBUS pin voltage