Multiswitch explanation
Operation principle
The multiswitch is a device, that is inserted between LNB and satellite receiver. From receiver’s point of view the multiswitch acts as an universal switchable LNB supplying signals in satellite polarization which must be requested using adequate control commands. Any receiver included in the distribution system has access to any channel broadcasted by a given satellite, which is the main advantage of using a multiswitch distribution.
In case of distribution of signals from more satellites, the multiswitch acts as group of individual LNBs switched using several DiSEqC switches. Again, any connected receiver can access any channel broadcasted by given satellite using standard control commands (analog + DiSEqC).
Scope of usage
Multiswitches are produced with 4 outputs as minimum. In some cases it may be favourable to design small distribution network for up to 8 user points using LNB Quad or LNB Octo instead of the multiswitch. Right decision requires considering all pros & cons of both variants from technical and economical point of view. The higher is number of received satellites and user points, the more complex becomes distribution network, especially with regard to length of cabling. In practise the distribution networks with multiswitches are constructed for up to 16 satellite polarities and up to 200 subscribers.
Satellite inputs and outputs
The multiswitch consists of several switches of satellite inputs, each switch serves one of the outputs. It is necessary to assign 4 inputs to any satellite to be received, each quartet is to be connected to one LNB. Using Quattro LNB (recommended), attention must be paid to proper interconnection with the multiswitch – confusion of cables results in loss of reception. Satellite inputs of the multiswitch are therefore properly marked:
- Vertical polarization, low band; marked A – V/L
- Horizontal polarization, low band; marked B – H/L
- Vertical polarization, high band; marked C – V/H
- Horizontal polarization, high band; marked D – H/H
Individual groups of 4 inputs are then marked as Sat System A, Sat System B td. etc.
Output ports are usually connected to wall outlets. During projection stage of installation it is advisable to consider the fact that modern receivers equipped with dual tuners require double connection to the multiswitch, occupying pairs of multiswitch’s outputs.
Compatibility with Quad LNB
Quad LNB is a satellite converter with 4 universal outputs. It provides required polarization&band on any of its outputs. If Quad LNB is connected to the multiswitch, control unit is no more the receiver but the multiswitch itself. Compatibility with Quad LNB means that the multiswitch is able to setup connected LNB in such a way that it acts like Quattro LNB (each cable connected between LNB and multiswitch permanently transmits different polarization&band). Note: using this feature it is possible to utilize Octo LNB as well.
Some multiswitches have an option to ensure Quad LNB support by means of levers of DIP-switch placed usually in a small window in metal body of the product. Using these levers, it is possible to switch off 22 kHz modulation to particular inputs which can be advantageous in some special cases (using Dual/Twin LNB).
Terrestrial input
The input for terrestrial signals is single and wideband. In case of use of several antennas it is required to combine outputs of all those antennas to the single cable. It is possible to use e.g. combiner of two UHF antennas C2/1ENP(U+U)-1, wideband amplifier A4/1+1EIT-7, or any suitable terrestrial headend.
Terrestrial input isn’t switched but splitted to all outputs where it is combined with satellite signals. In case of so called passive multiswitch the terrestrial band suffers from relatively high splitting loss. On the contrary, availability of return path (required in DOCSIS and similar application) is an advantage.
Where high terestrial insertion loss is not acceptable a multiswitch with so called active terrestrial input is the right choice. It includes an amplifier that covers the splitting loss.
The multiswitches ranked in Profi Class offer choice of passive / active mode selectable by the user or installer according to local reception conditions. This can be accomplished either by dedicated lever of DIP-switch or by a turning knob close to the terrestrial input.
The Profi Class multiswitches offer also DC voltage 12 V on terr. input fused to 100 or 150 mA which can be used as power source for an active terrestrial antenna.