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 cross-
modulation and intermodulation problems.
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