Remove All satellite system hardware , diplexers , splitters , amplifiers , power supplies , power injectors.
As a -->Test<-- of reception , run a Looooong coax through the house from the splitter port that connects to the directtv run of coax. Run the Looooong coax to the Tv that has half the channels.
Do not have the Direct Tv coax run connected.
As a -->Test<-- , can also change/switch the coaxes at outputs of the 2 way splitter.
Put one coax on one output port and the other coax on the other coax port.
Also the Tv that is getting 'half the channels' needs to scan for the Digital Broadcast Tv channels , not cable tv channels.
Go into the Tv menu and select , 'Air Channels' / 'Antenna Channels'.
Scan for Digital Broadcast Tv channels.
Not cable tv channels.
Digital Tv tuners can develop - Digital Glitches - that are not cleared out with a simple channel scan.
Do a Double Channel Scan ,
http://www.dtv.gov/rescan.html.
Also can put a Tv that is receiving "all" the channels at the location of the tv that is only getting half the channels.
This is all a process of elimination to find the , disconnected coax , bad coax , bad connections , the bad splitter , the bad Tv and etc..
Can also connect a inline coupler in place of the splitter that sends the signal to the Tv that gets 'half the channels'.