We have an antenna mounted around 15 feet in the air with around a 20 ft run of RG-6 cable to a grounding block. The ground block is not grounded though just used as a coupler. After the grounding block a run of around 30 feet of brand new RG-6 is used and goes into an ancient two way splitter behind the tv. The two leads are then two short equal lengths of RG-6 cable one going to the TV and the other to the HTPC for recording. The system works great for many channels but suffers with some. When the HTPC is on no matter playing a stream of just idling certain channels on the TV go out. Once the HTPC goes off the interference stops and it works perfectly fine. I have tried directly connecting the wire to the tv bypassing the splitter and DVR and the same results occur. The HTPC and TV are both plugged into an expensive surge protector. Does anyone have any idea what this could be or how to fix it? I am assuming its some type of interference from the HTPC but I cant figure out what it could be. On a second note similar occurs when the microwave on the opposite wall a room away is used. When powered on the TV signal goes completely out. The microwave is on a complete separate electrical circuit and the only connection I can find is that the cable from the antenna runs on the wall outside behind the microwave but there is Sheetrock, insulation, plywood, and siding between them. I am not sure if they are somehow connected. Does anyone have any idea what the interference can be? I am more concerned about the HTPC and TV operating at the same time then the microwave. I have read some things about grounding and how it may help to ground the antenna to the main houses electrical ground but that over 20 feet from the exterior grounding block.