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4.2
RF Antenna Connections
The transmit and receive antenna RF connection are made using two separate connectors. Coaxial
cables from the receive and transmit antenna must be connected to the Type-N (Tx) and BNC (Rx)
connectors. The position of these connectors is shown in Figure 4-1. For repeater use, the anten-
nas need adequate isolation between them, or if one antenna is used, the duplexer needs to have
adequate isolation between the Tx and Rx ports. The isolation requirements are unique to each
band and are shown in the table below:
If the duplexer isolation is not adequate, a preselector may also be used.
4.2.1
Duplexer Selection
The selection of a duplexer is critical to system performance. The use of a notch (band reject) du-
plexer is possible in some systems that are not located at high RF density sites.
The duplexer must be able to handle at least 50 W continuously. For the best system performance,
the insertion loss should be less than 2 dB. If the repeater is used in higher RF density sites, the
use of a pass-notch duplexer is recommended.
4.2.2
Antenna Selection
The selection of the antenna is critical to system performance. The selected antenna must be 50
Ohm impedance and capable of at least 50 Watts. Gain antennas may be used to increase system
coverage. Please take note of licensing restrictions when selecting gain antennas. Some services
or regions may have antenna gain or system ERP limitations.
The antenna must be connected to the duplexer with a high grade 50 Ohm transmission line (hard-
line). The line must have connectors to match the connectors on the duplexer and antenna.
Frequency Band
VHF
UHF 1
UHF 2
The repeater can key up at any time due to input from a subscriber unit or a
CW ID. Please ensure that all power is switched off before disconnecting the
transmit antenna.
It is important that all antenna cables are grounded at the point they enter
the building.
The antenna design is the customer's responsibility. All aspects of the
antenna design must comply with the relevant local regulations.
Chapter 4 Electrical Connections
Bandwidth
Isolation
136-174 MHz
85 dB
403-470 MHz
75 dB
450-512 MHz
85 dB
Page 17
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