Handbook

Denver Channelised CE
User/Maintenance Handbook
Handbook Nō.-50-063708HBKM Issue No:-2
Date:-03/11/2003
Page:-
10 of 51
2. OVERVIEW/SYSTEM DESCRIPTION
The equipment covered in this manual is a UHF Bi-directional Amplifier (also known as a
Repeater). Its main sphere of application is in urban areas where the topography is such that
shadows occur in the propagation pattern (for example within large buildings, conference
centres and tunnels, etc.)
The Amplifier is a 4-port device for direct connection to two Base facing antennas, usually a
highly directional Yagi or similar aligned towards the base (donor) site, and two radiating
cable feeders to cover the mobiles. The channel frequencies passed by the Amplifier are set
as per the specific customer requirements. In this instance, the channel module frequencies
have been ‘hard-wired’ and so it is not possible to change frequencies without some re-
configuration of the channel programming.
The system for which the Amplifier is to be used with is mainly duplex channel UHF radio
system but with a single simplex channel. The duplex channels operate constantly in each
direction using the Base Antenna port 2 and Radiating Cable port 2. There are five
Downlink (Base Transmit) duplex channels and four Uplink (Base Receive) duplex
channels. In addition there is the Uplink simplex (talkaround) channel operating via these
ports.
The Downlink simplex channel operates through the Base Antenna port 1 and Radiating
Cable port 1 ports. This is to avoid any interaction between the common frequency channel
high gain paths. Using separate antennas adds the isolation required for the simplex part of
the Amplifier to work.
The simplex channels are not constantly operating in their entirety. Instead, each simplex
path has the output amplification disabled and when an input is detected in one path that
amplifier will be switched on and the other path will be held off until that input signal has
stopped. In this way, the simplex part of the system is constantly ready to pass the channel in
either path.
The Bi-directional Amplifier consists of six different 19” rack mount 4U chassis. These are
a Base side Duplex/PA chassis (AFL part: 50-063702) to provide the link with Antenna 2
and the remainder of the system. In addition there is a Tunnel side Duplex/PA chassis (AFL
part: 50-063705) to connect the Radiating cable 2 to the remainder of the system. The
channel selectivity is made in the Downlink by a Downlink Channel chassis (AFL part: 50-
063703) and in the Uplink by the Uplink Channel chassis (AFL part: 50-063704). The
Downlink simplex channel and part of the Uplink simplex channel circuit is housed in the
Simplex chassis (AFL part: 50-063706) and there is a Power Supply chassis (AFL part: 50-
063707) to provide the DC supply to each of the five RF units.
The Bi-directional Amplifier is housed in a single 38U 19” rack. All external connections
are made towards the bottom of the rear of the rack suitable for cable entry via cable ducts
through the open underside of the rack. External connections are for the 110V AC input,
four ‘N’ type female RF connectors and a Krone block for the alarm output.