Installing a Two LNB Multi Switch

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22 September 2005

Installing a Two LNB Multi Switch

What is an LNB multi switch? A multi switch is different from a DiSEqC switch or a 22khzswitch in that it enables more than one receiver to use an LNB at the same time . How? Ratherthan switching the LNB between the receivers, the multi switch moves the receivers between theLNBs. And each receiver is connected independently of the others. A basic diagram is drawn

below.

The benefits? You can have more than one receiver using an LNB at a time with very little signalloss. It gives full choices of all transponders (on the same polarity – i.e. either horizontal orvertical) to each receiver.

How do you connect it? Here comes the part that needs a little bit of thinking. First you need tounderstand how the multi switch changes between LNBs. Look at the picture below:



Notice that the LNB connections are labeled LNB V and LNB H. When a receiver sends down the

coax to the LNB, and the switch, an 18v signal to tell the LNB to select horizontal polarity, theLNB switch first selects LNB H and then allows that voltage to pass on to the LNB connected tothat port. If the receiver instead sends the 13v vertical voltage, the switch would select LNB V andthen pass on that voltage to the LNB connected to that port.

Now you will realize immediately that you select, during the setup of the receiver (or it may bepreprogrammed), the polarity chosen for each satellite channel. You may also be aware thatvirtually all of the Ku Band satellites are currently vertical transmission, whereas many of the CBand satellites are horizontal transmission (some are both).

This presents a problem. If you want to have a LNB on LNB H port that is to receive from avertical transmission, your receiver will change the LNB polarity to horizontal and stop yourreception. What do you do? First lets consider what happens inside an LNB when you select the

polarity.

Polarity Selection: Inside an LNB is two small antenna. Depending on the voltage the satellitereceiver sends down the coax cable, the LNB will select to receive from either the vert ical or thehorizontal antenna. The antenna are 90deg apart. If you were to look down the throat of the LNBit would look something like this:

If you were to rotate the LNB 90deg it would look like this:



Now when your receiver selects the 18v horizontal polarity, it actually receives the vertical signalsbecause the horizontal antenna is aligned vertically. It does not matter which direction (i.e. – clockwise or anticlockwise) you turn the LNB, as long as it is 90deg difference.

Quick Guide Dish Setup: Align your dish and LNB exactly how you would normally do it. If youhave a twin LNB system (with two separate LNBs per dish) then test them individually as theyare.

Next decide which LNB will be on which port of the switch and then rotate the LNB to suit.

Lastly change the settings in the receiver menu so that the receiver selects the correct port for

that satellite. Further explanation below.

For example: Say you wanted to receive from Optus B1 and Optus C1 on a twin dish system likethe picture below. We want to receive off both of these satellites on vertical polarity.



You set up the system and test each LNB and the channels from that satellite. Then we decide toconnect the Optus B1 LNB (the LNB in the right of the picture on the stainless steel arm) to theLNB V port on the switch. We do not adjust this LNB in any way . Just connect it. Nor do we need

to change anything in the receiver menu for Optus B1 because we want to receive verticalchannels.

However the Optus C1 LNB (the one in the left of the picture, in the plastic mount) will need to berotated 90deg (either way). This is because it will be told by the receiver to change to horizontalpolarity. Now we change the setting in the receiver menu to select 18v horizontal for Optus C1(refer to your user manual or retailer for help on doing this).

Now when your receiver selects any channel from Optus B1, the switch will select that LNB viaLNB V port. When you select any channel from Optus C1, your receiver will switch to that LNB bytelling the switch you want horizontal signals, it will also switch your LNB to horizontal polarity – but you have tricked it by turning your LNB 90deg and so you will still get your vertical channelsoff Optus C1. And so will two other receivers in your home.

When is the Multi Switch not used? If you are receiving from a satellite that beams to NewZealand on both horizontal and vertical polarities then you can not use a multi switch because theLNB is stuck in one polarity setting. If you change the polarity setting, a different LNB is selected.However for the most popular Ku Band channels, such as those on the Optus satellites, this is agreat way to have more than one receiver in your house, because they are only on one polarity.

Final notes:

This switch is suitable for mounting outside, preferably under some cover such as the eave of ahouse. However F connectors with a waterproof seal must be used, a drip loop must be put in thecable run and we suggest sealing the connections further with silicon sealer or self amalgamatingtape.

Hook Technologies also manufacture a special Twin Sat LNB for 60-65cm dishes that alreadyhas one LNB rotated 90deg. This LNB in designed to receive from Optus B1 and C1 or Optus B1and B3 using a LNB multi switch.

All guide sheets are checked for errors, but remain as guide sheets only, not full instructionmanuals. For further information visit www.hooktech.co.nz

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Installing a Two LNB Multi Switch