900 MHz radio link between two remotely located Weather Stations

1

Base Station

:Sanjaya Gurung

Remote Station

900 MHz

Required EquipmentsLocal 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

RF401

900 MHz radio modem

Operating frequency range: 910 - 918 MHz

Supports point-to-point and point-to-multipoint datalogger communications

RF401

RF401

Antenna can be replaced with any other frequency compatible antenna according to the transmission range need

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

Connection Set-Up

5

Weather StationDatalogger(CR1000)

RF401

CS

I/O

Remote Weather Station Local Weather Station (Base Station)

CR206

RF401

Yagi (directional antenna)

Omni-directional antenna

900 MHz link

Sensors

Power Supply: 12 V battery, charged with solar panel

Power Supply: Powered by CR1000

Technical Specifications

6

Operating frequency: 900 MHzType: Frequency hopping spread spectrum TRx

Point-to-Point/Point-to-multipointI/O Data rate: 9600 bpsTx power: 100 mWTx range: 0.25 – 5 miles (omni-directional antenna) 10 – 20 miles (9 dB directional antenna) Rx sensitivity: -110 dBm

Power requirement: 9-16 V…12 Vdc (nominal)Avg.Current Drain: <1 mA..standby 24 mA while receiving <75 mA while transmittingCommunication Port:

9-pin serial CS I/O – connection to CR2069-pin serial DCE RS-232 – connection to PC

Default protocol setting: Transparent protocolDataloggers: CR200-series, CR10X, CR1000 etc.

RF401

Technical Specifications (contd..)

7

Operating frequency: 915 MHzCommunication port: 9-pin serial RS-232: Connection to PCPower requirements:

7-16 Vdc (12 V nominal)Avg.current drain: 0.2 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- C1Antenna port: 1 antenna portPulse Channels: 2 (P_LL and P_SW)Operating system: PakBusSoftware Support: ShortCut, PC400 or LoggernetAnalog voltage range: 0 to +2500 mVOn-board 12 V dc lead acid battery charger

CR206

900 MHz signal propagation

8

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

MW frequency range: 300 MHz – 300 GHz

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) = 32.4+20log(f)+20log(d) MHz km

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)

Antennas

Omni directional antenna(14203) 3 dB with cable clamp mounts

Yagi:14201

Directional antennaYagi antenna (14201): 9 dB

N female connector attaches to an antenna cableRequires COAXRPSMA-L or COAXNTN-L Omni-directional:14203

Transmission Range of RF401

Ideally, With 3 dB Omni-directional antenna (14203): 0.25 – 5 milesWith Yagi 9 dB directional antenna (14201): 10 – 20 miles

Antenna Gain Transmission range

Depends upon the selection of antenna