Motorola DR 3000 - Manual (Page 18)

6866576D02 June 13, 2007
Electrical Connections: RF Antenna Connections 4-3
4.2 RF Antenna Connections
The transmit and receive antenna RF connection are made using two separate connectors. Coax
cable from the receive and transmit antenna must be connected to the N-type (TX) and BNC-type
(RX) connectors. The position of these connectors is shown in
Figure 4-1 . For repeater use, either
two antennas with adequate isolation (75 dB - UHF and 85 dB - VHF) between them, or one antenna
and a duplexer with at least 75 dB - UHF and 85 dB - VHF isolation between the TX and RX antenna
ports is required.
4.2.1 Duplexer Selection
The selection of the duplexer is critical to system performance. The use of a notch (band reject)
duplexer is possible is some systems that are not located at high RF density sites. A duplexer like
the HFE8400 (406 – 450 MHz) or RFE4000 (450 – 470 MHz) or HFD8465 (150 – 160 MHz) is
adequate. Note that these duplexers are good for 4 to 7 MHz TX/RX spacings. Select another
duplexer for other TX/RX spacings.
The duplexer must be able to handle at least 50 Watts continuously. For the best system range, the
insertion loss should be less than 2 dB. If the repeater is used in higher RF density sites, the use of a
bandpass 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
(Heliax). The line must have connectors to match the connectors on the duplexer and antenna.
For proper antenna installation, please also consult the
Motorola Quality Standards Fixed Network
Equipment Installation Manual R56 (6881089E50).
The repeater can key up at any time due to input from a subscriber unit or a
CW ID. Please insure 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.
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