PLANAR-SG2000

Head-end “PLANAR SG2000” is used to amplify and equalize TV broadcast signals in range 48…862MHz in small CATV networks.

Head-end “PLANAR SG2000” (further GS) has some function features compared to another models of the similar GS class.

• GS channel filters have fixed (non-programmable) tunings on user’s demand channels to get high selectivity and small level deviation in channel passband.
• MMDS amplifier allows to receive TV signals from MMDS converter. MMDS module has AGC system to stabilize MMDS packet output level.
• AGC in every channel supports the constant output level in every GS channel at the season and other deviations of input radio signal levels (up to ±10dB).
• Built-in signal level display allows to exclude measurement equipments while the installation stage and keep up with the ethereal condition while the operation stage.
• Built-in attenuator allows to set the optimal input signal level to get max functioning AGC range.
• Equalizer in the output amplifier allows to compensate TV cable parameter deviation.

The structure scheme of 14-channels head-end “PLANAR SG2000” is shown in Fig.1 (power supply is shown conditionally).

Fig.1. “PLANAR SG2000” structure scheme

Fig. 2. The head-end structure scheme with MMDS signal reception possibility

“PLANAR SG2000” head-end basically contains VHF and UHF channel modules, every module performs independent channel filtering and signal amplifying of two or four channels.

Besides, the head-end can contain KV1 converter modules. KV1 converter is used to convert one channel of UHF range to a signal of another channel of VHF range. The head-and can contain MMDS module, which is used to amplify MMDS TV signals. In this case, the output amplifier is used with a diplexer, which sums TV ethereal channels and MMDS channels. The MMDS signal bandwidth is located in the upper part of UHF frequency range. It is necessary to have a protect interval between ethereal channels and MMDS channels (at least 48 MHz). In case of hitting ethereal channels into the protect interval band or into MMDS band, it is necessary to convert ethereal channels in VHF range with help of KV1 converter.

A four-channel module has two inputs and one output. Depending on customer demands, there are three versions of input connections:

• The signal from the first channel is divided into all four channels;
• The signal from the first channel is divided into three channels, the signal from the second channel is passed to one channel;
• The signal from every channel is divided into two channels.

Two channel modules have one input and one output.

KV1 converter module has one input and one output.

The structure scheme of VHF4 module is shown in fig.3. The structure scheme of UHF module has equal construction.

Fig.3.VHF4 module structure scheme

Signals from channel module outputs are sum in the four-input wideband power amplifier. This amplifier has an additional input for cascading.

The head-end is made in eight-channels or fourteen-channels constructions.

The construction including modules, the wideband power amplifier and the power supply is called the base block. The construction including modules and the combiner is called the case. If the base block is full value head-end, so the case is used for cascading (to increase the number of channels). In separate cases (if the number of channels more than 14-16), an additional power supply can be included.

Fig. 3. Module locating versions for eight-channel construction

Fig. 4. Module locating versions for fourteen-channel construction

The head-end has a built-in power supply. There is a pass of power supply+12V to each input of the head-end for feeding outer devices. This pass can be disconnect independently from every input if it is necessary.

In practically, the head-end construction modularity and easy-to-change configuration of four-channel module input parts allows to solve most problems of the broadcast reception (e.q., different directions and levels of reception signals).

While reception of all channels from one direction, the head-end can be built without additional inputs (the head-end configuration is built while ordering).

The special attention while designing the head-end was paid the simplicity to come into operation. The built-in input level display allows to avoid using the measurement equipment while the first (or test) installation. The every input attenuator allows to set the optimal level of the input signal to reach AGC max work range. While reception TV signals of one frequency range with large difference level (more 10 dB), it is recommended to place power and weak channels in different channel modules (talking while ordering). The built-in output attenuator allows to set the head-end output level depending on the number of channels. The slope control allows to compensate the cable performance deviation.

AGC system keeps season and other deviations of the input radio signal up to ±10 dB to simplify the head-end operation.

The head-end can be completed by different power supplies (15 V 2 A or 15 V 1 A). Fourteen-channel and sixteen-channel versions of the head-end are completed by BP15/2 power supply. Depending on module types, eight-channel version of the head-end can be completed by 1A power or 2A power supplies.

The technical specification of “PLANAR SG2000” head-ends is complied technical demands on CATV equipment confirmed by Russian Communication Ministry dated 14.07.96; RFSC standards 21-86, GOST 7845-92, GOST 28324-89, GOST 12.1006-84 SSBT, GOST 12.2008-87.