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Splitters and SWM Signal

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3 replies to this topic

#1 OFFLINE   sysakpa


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Posted 08 January 2013 - 12:41 PM

I am pretty new to this industry so this question will probably be easy for most to answer.

What exactly is a SWM signal and how is it different from the signal a conventional multiswitch uses and outputs?

If not already answered from your description above, why can one use a splitter after a SWM but not use a splitter after a conventional multiswitch? I was told that it does not even have to be a SWM splitter.
From my basic knowledge I was told that the different voltages that receivers send to the LNB would "interfere" with eachother after passing through the splitter on its way to the LNB. Does this "interference" occur only when the voltages are different or does it occur even if they are the same?

Why is this "interference" not an issue with a SWM? Is it because each line from this multiswitch can carry up to 8 tuners?


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#2 OFFLINE   veryoldschool


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Posted 08 January 2013 - 12:53 PM

Non SWiM uses 13 & 18 volts to both power the LNB and select which polarization is needed for the channel. It also uses a tone to change which LNB.

SWiM is a completely different method. Each receiver sends a request over a 2.3 MHz signal to the SWiM, and the SWiM then tunes to the transponder and converts the signal to one of eight frequencies for the receiver. These eight frequencies are all different, so they can be carried on the same coax without interfering, so the coax can be split.

A crude way to explain this is the SWiM is a pre-tuner before each receiver.

#3 OFFLINE   dielray



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Posted 08 January 2013 - 07:39 PM

To add more information:

A transponder is just a downlink frequency range. Each transponder can hold a number of channels.

The difference between multiswitch and SWM is how the signal is organized.

A multiswitch Ka/Ku system breaks the signal coming from the satellites into 4 parts. There are many transponders in any one part, even though a tuner will only ever use one transponder. The transponders that are in one part cannot be mixed and matched with another part. For example, a 13 volt part will only carry odd numbered transponders and will never carry even numbered transponders. This is the "interference" you were talking about. If you split this type of system, it will only work for as long as they are both looking at the same part. If you have two tuners requesting different parts only one wins out, leaving the other one searching for satellite or displaying the wrong channel.

SWM allows any 8 transponders to be chosen and passed down one cable. This is basically mixing and matching transponders. This type can be split because even if a tuner is looking at a certain transponder, another tuner can always see the transponder it's looking for.
DirecTV Technician
My thoughts and opinions are my own, and do not necessarily represent those of DirecTV, my HSP, or anyone else.

#4 OFFLINE   carl6


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Posted 08 January 2013 - 11:49 PM

In addition to the above, a lot of information here: http://hr20.dbstalk....d Cable FAQ.pdf

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