Two cables from the dish for dual tuners - why not split??

[matt33]

Hi all..

New to DirectTV and curious why you cant simply split the cable at the HR20 rather than run two cables all the way from the dish?

Thanks
Matt

[captain_video]

Because the signals are of two different polarities. When you tune to a channel, the receiver sends a signal back up the line to the LNB to switch to the correct transponder. The receiver sends either a 13-volt or 18-volt signal to the LNB to select the correct polarity that corresponds to the transponder it is requesting. If you split the signal and the two receivers request transponders of different polarities then only one can be chosen since they share a common feed from the dish, resulting in no signal on one of the receivers. It becomes even more complex when you try tuning to the 110 and 119 sats because there's an additional 22kHz tone used to select those transponders along with the DC voltage. The bottom line is that each tuner must have a dedicated feed from the dish to avoid tuning conflicts.

[TriggerDeems]

Because the signals are of two different polarities. When you tune to a channel, the receiver sends a signal back up the line to the LNB to switch to the correct transponder. The receiver sends either a 13-volt or 18-volt signal to the LNB to select the correct polarity that corresponds to the transponder it is requesting. If you split the signal and the two receivers request transponders of different polarities then only one can be chosen since they share a common feed from the dish, resulting in no signal on one of the receivers. It becomes even more complex when you try tuning to the 110 and 119 sats because there's an additional 22kHz tone used to select those transponders along with the DC voltage. The bottom line is that each tuner must have a dedicated feed from the dish to avoid tuning conflicts.

Precisely what he said, at least for now. Technology being tested right now called SWM (single Wire Multiswitch), which will probably be available to all in the next few months, will permit a splitting of the signal, and require only one cable run.

[Tom Robertson]

Welcome to the forums! :welcome_s

Each tuner can request 1 of 4 different set of signals to be sent down (up to 6 if you have the extra dishes for locals on 72.5 and international channels). Since each tuner is independent and could request a different set, each needs its own link to the dish (or multiswitch).

SWM fixes this by sending just one transponder down the coax instead of all the even or odd transponders down. Some cool technology, actually.

Cheers,
Tom

[kevinturcotte]

Got me curious now. What if you did split the signal and tuned each tuner to a channel on the same satellite/transponder? Would they both actually get a signal, or would the splitter still kill it (Provided the splitter was designed to deal with the correct frequencies)? I know, no possible use for it, just curious.

[veryoldschool]

Got me curious now. What if you did split the signal and tuned each tuner to a channel on the same satellite/transponder? Would they both actually get a signal, or would the splitter still kill it (Provided the splitter was designed to deal with the correct frequencies)? I know, no possible use for it, just curious.
The even/odd transponders are controlled by 13 or 18 volts. If you split them and one receiver was sending 18 volts, it would over power the other receiver with 13 volts.

[CCarncross]

Thats about how it would work. As long as each tuner was requesting a channel coming from the same signal type, 18v/13v, 22khz/no 22khz tone, then yes, it works, but of course thats just crazy to set it up that way.