TV & SAT TV
In the Home
Switches, combiners and diplexers used in individual satellite installations
The reasons for using switches
Nowadays individual satellite installations are rather rarely used for receiving channels from one satellite only, with one satellite receiver. Most of users prefer to have access to a variety of programs from two or more satellite positions, so that next converter/s (LNB) will have to be installed. The most common situation is reception from two satellites, which requires installation of two converters. It means that we should lead two cables to inputs of the receiver.
Unfortunately, digital satellite receivers are usually equipped with one input only, therefore connection of two converters can be realized only through an external switch.
- manual, practically not used,
- controlled by Tone Burst signal,
- controlled by DiSEqC signal,
- controlled by the level on 8th pin of Euroconnector (SCART)
- controlled by the slope on 8th pin of SCART
- controlled with 22 kHz signal.
Construction of electronic switches.
Each switch consists of simple logic IC and switching circuit. It is programmed micro controller in the case of switches controlled with signal DiSEqC or Tone Burst, which detects and decodes DiSEqC or Tone Burst. For switches controlled by level it is voltage comparator and for switches controlled by slope - bistable trigger. Switching circuit is mostly realized with the use of transistors and relays.
Relays is used to connect power voltage to active converter and to pass signal from converter to a receiver. In the case of transistor switch, transistors are only used to switch on the power voltage, and satellite signal is being carried by shunt capacitors of collector - emitter of transistors, that is mostly any low power, low frequency transistors. Sometimes relays are also shunted by additional capacitors, to decrease attenuation of satellite signal.
Switch controlled by the Tone Burst signal.
This solution enables fully automatic switching of converters. It should be remembered that it requires the receiver is equipped with Tome Burst control, sometimes called DiSEqC-Mini. Some digital receivers and many analog ones enable generation of this signal. It is needed to assign Tone Burst signal to each satellite in the receiver's menu. There are two signals available: Tone Burst: A and B, what means that only two converters can be connected to that switch.
Diagram of connection of two converters chosen by Tone Burst switch
Switch controlled by DiSEqC signal.
It is the best solution, because it enables fully automatic switching of even four converters. The receiver has to support at least DiSEqC 1.0. Most of digital receivers enable generation of this signal. It is needed to assign DiSEqC signal to each satellite in the receiver's menu. There are usually 4 orders available: A, B, C and D, what means that four- input switch can be connected, and as a conclusion, we have access to four converters.
Diagram of connection of four converters controlled by DiSEqC switch
Two receivers and two converters. We present here installation enabling independent receiving of channels from two satellites, with two tuners. To achieve that, the dish has to be equipped with double mount for two employed twin converters, and we need two DiSEqC switches. It is very important to use switches with high separation between inputs, at least 25 dB. Otherwise, due to simultaneous signal transmission on both inputs, receiving won't be possible. We recommend switches S.166-A R852505. In its catalog page there is put updated diagram showing practical implementation for two receivers and two LNBs, allowing reception of terrestrial TV as well.
The concept of independent reception of programs with two receivers
Receiving from four satellites. We increasingly receive inquiries about possibility of connecting more than two converters to one tuner. It is possible and simple when a receiver supports DiSEqC. Usually in setting menu of relevant satellite the field named DiSEqC appears where it's possible to choose options (DiSEqC 1, DiSEqC 2, DiSEqC 3, DiSEqC 4 or DiSEqC A, DiSEqC B, DiSEqC C, DiSEqC D). We choose different option for each satellite and we link adequate switch connector with each satellite converter. We recommend 4/1 switch SPU 41-02 4/1 R852484.
Reception of programs from 4 satellites; obviously 4 separate dishes can be used - then it is possible to receive broadcasts from satellites placed in any angular distance
Example of diplexers use made by Terra and Alcad companies
Diplexers allow for using single cable to transmit signals of first satellite IF and terrestrial television signals. They are built with the use of high pass and low pass filters, additionally they enable to power converters from receiver's input (they pass DC current in satellite path, and optionally in terrestrial path - in case of employing amplifiers).
Satellite diplexer - principle of operation
Satellite diplexer enabling to power preamplifier - principle of operation
Choosing satellite diplexer it is important to take into consideration possibility to power terrestrial TV preamplifier. For example, the R85311 model does not provide the possibility, whereas the R85312 item supplies stabilized 12VDC continuously. Possible way of powering a preamplifier is also dependent on the feature of SAT receiver - supplying LNB in standby mode.
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SMATV Systems (9)
Some Theory (14)
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