900 mhz radio link between two remotely located weather stations 1 base station :sanjaya gurung...
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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
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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
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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..)
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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
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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