1. 900 MHz radio link between two remotely located Weather Stations
:Sanjaya Gurung
900 MHz
Base Station
Remote Station

2. Required Equipments Local Station: RF401: 900 MHz radio modem
Appropriate antenna and connecting cables
Compatible Datalogger or PC
Power Supply
Remote Station:
CR206: Datalogger having built-in 915 MHz radio
Appropriate antenna and connecting cables
Power Supply
Datalogger support Software

3. RF401 900 MHz radio modem Operating frequency range: 910 - 918 MHz
Supports point-to-point and point-to-multipoint datalogger communications
RF401
Antenna can be replaced with any other frequency compatible antenna according to the transmission range need

4. CR206
CR206 is a datalogger to measure a few sensors and transmit data using built-in 915 MHz spread spectrum radio
6 Kbyte program storage
Powered by 12 V battery
CR206

5. Connection Set-Up Weather Station Datalogger (CR1000)
Omni-directional antenna
Yagi
(directional antenna)
RF401
RF401
900 MHz link
Power Supply: Powered by CR1000
CS I/O
CR206
Weather Station
Datalogger
(CR1000)
Power Supply: V battery, charged with solar panel
Sensors
Remote Weather Station
Local Weather Station
(Base Station)

6. Technical Specifications
RF401
Operating frequency: MHz
Type: Frequency hopping spread spectrum TRx
Point-to-Point/Point-to-multipoint
I/O Data rate: bps
Tx power: mW
Tx range: – 5 miles (omni-directional antenna)
10 – 20 miles (9 dB directional antenna)
Rx sensitivity: dBm
Power requirement: V…12 Vdc (nominal)
Avg.Current Drain: <1 mA..standby
24 mA while receiving
<75 mA while transmitting
Communication Port:
9-pin serial CS I/O – connection to CR206
9-pin serial DCE RS-232 – connection to PC
Default protocol setting: Transparent protocol
Dataloggers: CR200-series, CR10X, CR1000 etc.

7. Technical Specifications (contd..)
CR206
Operating frequency: MHz
Communication port: 9-pin serial RS-232: Connection to PC
Power requirements:
7-16 Vdc (12 V nominal)
Avg.current drain: mA (quiescent period..radio turned off)
20 mA (radio always on)
Single Ended Channel: 5 (SE1-SE5)
Excitation Channels: 2 (Ex1 and Ex2)
Control Ports: 2 (C1, C2)…SDI 12- C1
Antenna port: 1 antenna port
Pulse Channels: 2 (P_LL and P_SW)
Operating system: PakBus
Software Support: ShortCut, PC400 or Loggernet
Analog voltage range: 0 to mV
On-board 12 V dc lead acid battery charger

8. 900 MHz signal propagation
MW frequency range: 300 MHz – 300 GHz
MW freq. range
(UHF) (0.3–3 GHz), (SHF) (3–30 GHz), and (EHF) (30–300 GHz) signals
UHF signals travel over LOS (Line Of Sight) distances
UHF: widely used in 2-way radio systems

9. Friis Radio wave transmission formula
At = Transmission line loss between transmitter and transmitting antenna
Ar = Transmission line loss between receiver and receiving antenna
FSL, At and Ar are the one which constitutes the attenuation of microwave signal.
FSL (dB) = log(f)+20log(d)
MHz km

10. Problems in LOS propagation
Obstacles between Tx and Rx antenna
Obstacles such as trees, buildings, high hills etc. lying between Tx and Rx antenna blocks or reflect/absorb/diffract the direct signal
Line of Sight between Tx and Rx should be clear for best reception of the transmitted signal at Rx (i.e. for best RSL)

11. Antennas Omni directional antenna (14203) 3 dB with cable clamp mounts
N female connector attaches to an antenna cable
Requires COAXRPSMA-L or COAXNTN-L
Omni-directional:14203
Directional antenna
Yagi antenna (14201): 9 dB
Yagi:14201

12. Transmission Range of RF401
Depends upon the selection of antenna
Ideally,
With 3 dB Omni-directional antenna (14203): 0.25 – 5 miles
With Yagi 9 dB directional antenna (14201): 10 – 20 miles
Antenna Gain
Transmission range