Selecting the right equalizer for an RF amplifier.

Transcription

1 Selecting the right equalizer for an RF amplifier.

2 Frequencies bandwidth and amplifiers selected for CATV-FC systems. 1- On a modern FC-CATV system, there are 2 types of RF amplifiers MINI-BRIGER and INE EXTENDER. 2- MINI BRIGER can have 2-3 and 4 outputs. 3- INE EXTENDER have only 1 output. 4- These 2 types of RF amplifiers usually requires a RF Equalizer that is situated before the first stage of amplification. 5- The values of these equalizers depend on the distance between the preceding RF amplifier or Optical node. 6- Modern CATV-FC system can have a forward frequency bandwidth from 50, 85 and 104 to and 1, The system usually carry 77 analogs channel and the rest of the spacing is use to transport digital channels. 8-Differents band width splits are used in Europe versus Canadian and USA system.

3 Bi-directional filters available on a RF amplifiers

4 RF Input of a modern FC-CATV for ,000 North America amplifiers ,000 RF Input of a modern FC-CATV for ,000 European amplifiers , The major difference between the American and European amplifiers is the frequency bandwidth, in North America the bandwidth of RF amplifiers starts at 50 and in Europe they start at 85 or All of the RF amplifiers use the same forward equalizers.

5 RF output of modern RF amplifiers with differents frequencies. From 50 to 46 dbmv 14 db for 1, db for db for db for 1, db for db for , Properly designed RF system must operate with a slope output to take advantage of better system distortion. 2- The operating slope change with the bandwidth of the system.

6 RF Input of moderns amplifiers with differents spacing between amplifiers , Amplifier for European and North America utilise the same amplifiers, the difference in frequency is set by the input and output I-OW filter at each end of the RF amplifiers. 2- Input equalizer are for every db of cable spacing in front of each amplifier. They usually go from 1 to 26 db in step of 1 db.

7 Different input level value for different RF amplifiers. MINI-BRIGER and INE EXTENDER 3 db -E input M-B input 1- MINI-BRIGER amplifiers require a flat input after the selection of the right equalizer. 2- INE EXTENDER amplifiers requires a 3 db TIT from the highest frequency and lower frequency. On INE-EXTENDER this 3 db lower input on lower channel is to help better output distortions and does not affect the CARRIER to NOISE of the INE EXTENDER due to the higher input of the INE EXTENDER.

8 Diagram for RF amplifiers with 2 outputs. This type of amplifier can have 3 or 4 RF outputs -20 db Test point -20 db Test point PAD EQ EQ PAD MAN AGC TC Return status PAD PAD EQ PAD

9 Diagram for RF amplifier, INE-EXTENDER 3 db TIT -20 db Test point -20 db Test point PAD EQ EQ PAD PAD MAN AGC TC Return status PAD EQ PAD

10 Finalising the RF output level adjustment. 1- After the selection of the right equalizer and proper pad, you now need to adjust the RF level of all amplifiers to the recommended output of the system. 2- In general these RF amplifier have 3 types of output adjustment. 3- Manual, where a pin diode regulates the RF output. It is usually capable of a play of 3 to 4 db but it as no control on the temperature swing. 4- TC often call TDU (Thermal Drive Unit), where the temperature of the housing control the RF output. In cold weather the level goes down and in hot weather the RF level goes up. Once properly adjusted the RF level should stay at the proper level during temperature changes. It is capable of controlling the RF output by +3 to -3 db 5- AGC often call ADU (Automatic Drive Unit) where a channel carry by the system is used to automatically keep the RF output on the proper level after a final adjustment. It is capable of controlling the RF output by +3 to -3 db 6- In cold country I recommend an amplifier with a TDU control where a ADU control should be places in the following amplifier and so on.

11 Finalising the RF output level adjustment. TDU NODE AMP E TDU AMP

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