X8200 Datasheet, PDF (17/19 Pages) rfsolutions.ltd – Synthesised Radio Modem

Synthesised Radio Modem
X8200
X8200HP
RU67 type and kept as short as possible. As a rule of thumb the RF power is halved
every 10m of antenna feeder. It is better to keep the signal wire long and the antenna
feeder short.
Type of Antenna used.
Surrounding Topography.
Interference for other networks operating on the same frequency.
The Weather.
Antennas
The main types of antenna used in telemetry applications are as follows:
Helical
End Fed Dipole
Yagi
Helical Antenna
The helical stub antenna is robust, low cost and physically small. It has a gain less than unity.
Range of up to 2Km.
End Fed Dipole
The end fed dipole antenna has a unity gain. Its main application is to provide cost effective
omni-directional radiation.
Range 10 to 20 Km
Yagi
This antenna has a high gain typically twice (3dB) to ten times (10dB) the input power in the
direction of orientation. It is the type of aerial commonly used in domestic televisions.
The output power of a transmitter connected to a Yagi antenna has to be reduced to conform
to the DTI specification. This has the advantage of reducing the overall power consumed by
the transmitter without effecting the range in the direction of orientation. It also reduces
interference from other users.
The receiver signal is also amplified if a Yagi antenna is used thereby extended range in the
direction of orientation to around 20 Km line of sight.
Antenna Alignment
If directional yagi antenna are used it is important to aligned them correctly. This can be
done using a compass and ordinance survey maps. The alignment can be checked by
selecting the Key Transmitter option at the transmitting station. A radio modem is then
attached to the yagi antenna feeder at the receiving station. By selecting the RSSI option in
the menu the yagi antenna can be rotated to a position of peak signal strength This will be in
the direction of the transmitter beacon.
Site Survey
First check the occupancy of all the radio channels at all the proposed sites. This can be
achieved by using an antenna, radio modem and PC. Select the RSSI option and observe
the bar graph. Note any activity. Go to the RF channel option and select the next RF
DS8200-2 April ’07
©2007 RF Solutions Ltd, www.rfsolutions.co.uk
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