User's Manual

COMTRAC RADIO
USER MAUAL
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DTC
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9950-15900
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12.2 Mobile Radio Unit
The MRU, or client radio, is situated on a train, and is connected to one of the two
independent vehicle on-board computer replicas. There will be one MRU at each end of
the train. The antennas for each MRU are connected at one end of the train only, and
setup with diversity. Each radio is powered by an independent direct current (DC) power
supply.
The link budget for each antenna connection must be the same to ensure antenna
diversity is optimized. This means the antenna cable type and length must be the same.
The distance between the two antennas is recommended to be greater than 5
wavelengths apart. One wavelength (λ) is about 12 cm.
Typical antenna is the Huber+Suhner Linear polarized antenna, 1324.17.0098, 8.5 dBi
or 1324.99.0025, 8.5 dBi.
Typical on-board installation is shown below.
Filter
Antenna
Diversity
Filter
>5λ
ComTrac Radio
MR
Figure 6 Mobile Radio Installation
12.2.1 Mobile Power Setting
When installing the mobile radio, the power level must be set in order to not exceed the
maximum output power and/or EIRP requirements for the region of deployment, which is
measured at the antenna output. In the configuration above, only one antenna will be
transmitting at any given time.
For mobile radio power level setting, the output power level should be the same as what
is set for the WRU, in order to produce a balanced RF link (same power level seen by