Labgear CM 7281, CM 7282 Installation Instructions Manual
CM 7281 VHF-UHF single input
CM 7282 VHF-UHF dual Input
MATV Distribution Amplifiers
Introduction and Applications
These fully screened amplifiers are ideal for handling TV and FM DAB radio signals in small and medium
sized MATV distribution systems. These amplifiers have a single output and are used in conjunction
with a passive distribution network built using splitters and taps (also available from Labgear). Advice on
the design of suitable distribution networks is available from Labgear's technical support department if
required.
CM 7281
This is a single-input wideband amplifier covering Bands I to V (40-862 MHz). It should be used
where the signals from VHF and UHF antennas have been combined before reaching the amplifier.
CM 7282
This type has separate VHF and UHF inputs, each with its own gain control. Separate feeds from the
antennas are required, but the ability to set VHF and UHF signal levels separately is an advantage. The
VHF operating frequency range of the CM 7282 has been configured for use in Bands I to 111(40-300
MHz).
Digital applications
Both units are suitable for handling digital terrestrial TV (DTT) signals in addition to the analogue services.
Distribution of DTT signals requires careful attention to system design and to signal levels for
satisfactory results.
Using a UHF pre-amplifier
In weak UHF signal areas, or where a long downlead cable run is required, it may be desirable to use a
masthead preamplifier mounted close to the UHF antenna. These MATV amplifiers feature built-in
12V input line-powering; there is no need to use a separate power unit for the masthead amplifier.-(Type CM 7282 has line-power on the UHF input only.)
The built-in line-power is rated at 40mA (fully short-circuit proof) and is compatible with the majority
of Labgear masthead preamplifiers.
Installation Instructions
The preamplifier gain used should be kept to a minimum and generally only needs to exceed the
down lead cable loss by about 6dB. A single-stage 15dB gain masthead (PUM111) will be suitable for
the great majority of applications. Use of excessive amounts of gain will lead to severe crossmodulation and intermodulation problems.
Installation
Important note:
attention is drawn to the GENERAL SAFETY PRECAUTIONS panel on page 4 which contains
advice relating to the safe installation and operation of these products.
Location
Choose a location for the amplifier from which it is convenient to run the antenna and outgoing system
trunk cables. Typical examples of suitable locations are a roof space or cupboard. In weak signal areas it
is helpful to keep the antenna cables as short as practicable. Select a cool, dry location to install the
amplifier. This means a location
Where the ambient temperature will remain between -10
°C and +40°C, and which is free from risk of
dripping or splashing water, etc. The fixing location should allow adequate access to the equipment
for wiring and maintenance. Clearance of at least 25mm should be allowed around the top and lefthand side of the unit for ventilation. More clearance will be needed under and to the right of the
amplifier to allow access for cables.
Fixing
The amplifier should be fixed to a wall or other suitable hard surface, using suitable screws and
masonry plugs (not supplied). The amplifier should not be left supported only by its wiring, nor
should it be left resting on a carpet or other insulating and/or inflammable surface.
Electricity supply
These amplifiers are not intended for domestic use and are supplied without a mains plug fitted. The electrical
supply arrangements to the unit should be in accordance with BS 7671 ('IEE Wiring Regulations'). Additional
information is given in the GENERAL SAFETY PRECAUTIONS panel on page 4.
The amplifier may be connected to the mains using either a switched fused connection unit, or a plug
and socket connection. The fused connection unit method reduces the risk of accidental
disconnection and is recommended.
If the amplifier is not connected using a fused plug or connection unit it must be protected at the
final distribution board by a fuse or MCB of rating not exceeding 6A. An isolating switch should be
provided near to the unit to allow it to be disconnected from the supply when necessary.
Signal connections
Input and output signal connections are made using Type-F (IEC 60169-24) connectors. CAI Benched
marked cable to EN 50117-2 should be used, in conjunction with high quality crimp F connectors. The
F connectors should always be tightened with a spanner; leaving them finger tight may result in
unwanted signal ingress or leakage, as well as suck-outs in the frequency response.
Monitor point
Each amplifier is provided with a -30 dB monitor point to allow the outgoing signal quality to be
checked using a spectrum analyser. Since the monitor point is of the resistive (non-directional) it
is not very accurate, for making accurate measurements of signal launch levels install a FHU301
Tap on the main output.
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