Just one more dumb dual LNB/Multiswitch question

[jpsage]

I have spent the past few weeks reading about LNBs and multiswitches and basically understand the idea except for one part.

If all the tuners are selecting RHCP (12 volts dc to switch), where does the multiswitch get the 18v for the LHCP? Does the switch have a power converter inside or do both LNB go to 12v? If you have an externally powered switch does it just select one LNB LHCP and the other RHCP?

Thanks,
john.

[veryoldschool]

I have spent the past few weeks reading about LNBs and multiswitches and basically understand the idea except for one part.

If all the tuners are selecting RHCP (12 volts dc to switch), where does the multiswitch get the 18v for the LHCP? Does the switch have a power converter inside or do both LNB go to 12v? If you have an externally powered switch does it just select one LNB LHCP and the other RHCP?

Thanks,
john.
A powered multi-switch drives the LNB(s) with 13 & 18 volts. With the 3LNB [and more] dishes, they add a 22 KHz tone, so there are four combinations 13/18 volt, tone/no tone.
If the multi-switch isn't powered, then the "tune signal" comes from each receiver, and if they're all tuned to RHCP, there is no 18 volts. Have one receiver tuned to RHCP and another LHCP, and you'll have 13 volts on one line and 18 volts on the other.

[BattleZone]

I have spent the past few weeks reading about LNBs and multiswitches and basically understand the idea except for one part.

If all the tuners are selecting RHCP (12 volts dc to switch), where does the multiswitch get the 18v for the LHCP? Does the switch have a power converter inside or do both LNB go to 12v? If you have an externally powered switch does it just select one LNB LHCP and the other RHCP?

Thanks,
john.

Let's say you have a 3x4 multiswitch (the 3 inputs are 2 sat and 1 OTA). There is an 18v and a 13v line from the switch to the LNB. If all of the receivers need RHCP transponders, then they're all putting out 13v. Thus, nothing is needed from the LHCP transponders, so the lack of 18v doesn't matter. Now, when one of those receivers DOES need a LHCP transponder, it switches to sending out 18v, and the switch then passes the 18v to the LNB, which energizes it and sends back the LHCP transponders.

With an externally powered switch, there is a voltage converter inside the switch that locks all 4 lines into their configuration, ensuring that each of the 4 possible signals are always available. This is why you might notice that channel changes are a little faster with a powered switch in some configurations.

[houskamp]

Let's make this easy.. it's not needed at the time so it doesn't matter that it's off..