TV Amplifiers - Classification
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Channel amplifiers (channel modules/inserts) - are used in medium and large-size installations (MATV/SMATV systems, headends). They amplify individual analog channels, or - in the case of digital TV - multiplexes carrying several digital channels. It means that they improve selectivity of the distribution path, amplifying the desired signal and practically eliminating the unwanted ones. Their main parameters are: operating channel, gain, maximum output level, selectivity.
Channel amplifiers, in comparison to other types of RF amplifiers, are characterized by a high gain, typically 40-54 dB, and a very high output level, more than 120 dB. They are dedicated for larger MATV/SMATV systems and their biggest advantage, besides the high gain and output level, is possibility of equalization of signal levels on each channel.
ZG Series of Alcad channel amplifiers provides maximum gain of 53 dB. Such high gain (in conjunction with very high maximum output level - above 123 dBuV) allows to distribute the channels in quite large installations, 200 outlets or so, without use of additional building amplifiers.
Channel amplifiers allow to adjust gain in the range of 20 dB. There is possibility of changing the amplified channel as well, however it has to be preformed by the manufacturer. There are many types of channel amplifiers with different parameters:
A set of channel amplifiers can also be placed in a rack cabinet, using the SP-725 R912037 frame (it can carry up to 9 ZG amplifiers).
Building amplifiers - are used in community installations and cable TV distribution systems. One building amplifier is usually used in one staircase or in a whole smaller building. The amplifiers have single broadband input, one output and often an additional test output (usually -20 dB).
They are equipped with power supply and ensure compensation of cable attenuation (it can be adjusted within 20 dB range). Typical noise figure is 8 dB, and gain 40 dB. Their advantage is high output level (usually 120 dBuV), a drawback - they are rather expensive. They are often equipped with return channel.
Multi-input building amplifiers - used in medium-size installations (up to 50 outlets). They have band inputs with adjustable gain, but no cable attenuation compensation. The amplifiers typically enable to power preamplifiers via coaxial cables, have one output and additional test output. They are equipped with own power supplies, but are more expensive than outdoor/mast amplifiers. Typical gain 35 dB, noise figure 7 dB, maximum output level 115 dBuV.
The most professional amplifier in this group is Terra MA-203 R82323. It has 5 inputs: 1 x FM / VHF I, VHF III and 3x UHF. Each input ensures separate gain adjustment; summing up the signals from the FM / VHF I, VHF III, and 3 UHF paths it is possible to attenuate some of the signals by using 10 dB attenuators. The UHF signals are combined in two stages: first, the signals from two inputs and then the signal from the third UHF input. This provides yet another opportunity to equalize the weaker and stronger signals. The amplifier has a very high output level: 119 dBuV for VHF band and 121 dBuV for UHF band.
Subscriber amplifiers - used in small installations (up to 20 outlets), have one broadband input and two paths with independently adjustable gain in VHF and UHF bands. Typically they allow to power antenna preamplifiers via coaxial cable. Their advantage is own power supply and low cost, similar to outdoor amplifiers (that are not equipped with own power supplies). Typical gain 24 dB, noise figure 2-4 dB, maximum output level 102 dBuV.
- CA-210 R90460 - for distribution of antenna signal in an apartment, house or small building, with low noise figure, may power a preamplifier (24 V),
- CA-215 R90461 - as above, may power a preamplifier (12 V),
- AI-200 R90450 - as above, no possibility to power a preamplifier,
- AI-223 R90452 - amplifier with 5-65 MHz return channel, for distributing cable TV in an apartment.
Band amplifiers and preamplifiers - used for amplification of low signals that are at levels below the specifications of channel or building amplifiers. They are quite cheap, especially compared with channel amplifiers. However, in very hard conditions there should be used special outdoor channel amplifiers located directly by the antenna. Typical noise figure is 2 dB, gain 20 dB. They have one input and are powered via coaxial cable.
Outdoor amplifiers. They are used in small installations and usually are equipped with band inputs with adjustable gain, but do not have cable attenuation compensation (as the lengths are short). The amplifiers allow to power preamplifiers placed in antenna boxes. Typical gain is at a level of 30 dB, noise figure 8 dB, maximum output level 110 dBuV. The amplifiers have only one output and are powered via coaxial cable. The main advantage is low cost, the drawback - exposure to environmental conditions which may increase failure rate.
|Number of inputs||4||4||3|
|Max output level [dBuV]||108||108||108|
|Gain correction [dB]||22/16||22/16||22/16|
|Noise figure [dB]||<5/<5.5||<5/<5.5||<4/<5|
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