See this post in the Switches Simplified FAQ, and look under:
- Special Case: old Primestar LNB
It applied directly to your two-LNB question, when used with modern FTA receivers, using voltage-controlled LNBs.
There has also been some discussion about the fact that one of the LNBs gets 18 volts, and the other only about 12 volts.
Some LNBs don't like the lower voltage.
And two solutions discussed (in other threads) include Power Inserters, or a modification to the MultiSwitch.
i have dual c and dual ku lnbs on my dish. my vertical lnbs only get 13v and work fine. my horizontal lnbs get the full 18v and work fine. I use powered multiswitches two of them.
one 4x2 for c band and one 4x2 for ku.
c band only would only require one multiswitch. I recommend a powered one out next to the dish to minimize the power loss from longer coax runs as far as the 13v lnb is concerned.
I have a Chaparral Dual C-Band feedhorn. I use 2 @ 1x2 HF splitters (one port power pass) and the power pass port goes to a 4dtv, while the other port goes to a 4x4 multi-switch to V/H respectively. The lnb's get there power from the 4dtv and both get 18 volts. The 4x4 switch feeds 4 DVB receivers.
This way I have 4 cables, 2 for the 4dtv and 2 for my DVB system
the signal stacked lnbf will not work with the dsr-922 because the IF frequency is different.
Most fta receivers can use it however.
I use a dsr-905 4dtv set to "dual c and dual ku lnbfs" in the antenna menu.
My chaparall orthomode dual c dual ku feedhorn (has two c lnbs and two ku lnbs) works like an lnbf but with a bit better performance imo.
My c-band lnbs are dms bsc211's. they work fine at 13v. I have fed them 18v before and cannot tell any signal quality increase at all.
My switches are in a plastic nema enclosure on the mounting pole at the dish to minimize the vertical's 13v low voltage losses.
I feed a 4dtv, pansat 9200HD, fortec ultra lifetime, old ariza fta box that i use to get equity channels from 123w ku. My 9200's new firmware from pansat does not allow equity's audio and video pids to scan in correctly making it impossible to receive some of the channels.
something screwy in the placement of the pids to show the video.