I'm having problems debugging the last of my Comcast CATV signal problems, and I was hoping someone might be able to give me some advice.
The 2 main TVs here are HD LCDs, with Tivo Series 3 PVRs connected to them, in two separate locations. Most of the HD channels we regularly watch, (local, and movie channels), we receive fine on both TV/Tivos. However, the main TV/Tivo is noticeably lower on signal levels, (using the crude signal meters in the Tivos as a point of reference), across the board. This lower signal level creates problems when watching a few HD channels, which include the local Fox affiliate, and channels like Animal Planet and AMCHD, ONLY on the main TV/Tivo. When watched, the reception results in some severe tiling, sprinkled with complete signal dropouts. Again, the secondary TV/Tivo, which has a stronger signal, shows no problems with all channels.
The main TV/Tivo, is a longer run of cable, about 100 feet, as opposed to 50 feet for the secondary location. All of these runs are brand new quad shielded RG6. The main run I've actually run twice, with no noticeable difference in the signal level. This main run does go under the house, as opposed to the secondary run which goes through the attic. The CATV distribution is in the attic and consists of the CATV input running about 30 feet to a Viewsonics 2 way splitter, which fed at first, 2 Viewsonics VSMA-608C-10R 8 way drop amps. I installed all 12 of my runs, and then terminated the 4 remaining ports. This did improve the main location signal levels, but the problem channels still showed some tiling and dropouts. I then swapped out one of the Viewsonics VSMA-608C-10R 8 way drop amps, for a VSMA-604C-10R 4 way drop amp, for just the long distance runs. Again the signal level improved slightly, but not enough to be watchable.
There are no splitters anywhere else. My cable modem signal values are Downstream SNR 33.403dB, Power 6.3dBmV, and Upstream 22.4 dBmV now, coming off of a port on the VSMA-604C-10R. As part of this CATV re-cabling/upgrade, I also installed a TII 212 Coaxial Lightning Surge Protector at the entry point to our home which I grounded. I also noticed that when I grounded the two Viewsonics drop amps, the picture on the problem location TV/Tivo seemed to improve a bit more, but again the dropouts make watching the channel impossible. So the system is grounded at the drop amps, and the main entry point, only.
I have run the main TV/Tivo cable twice, but I ran it along the same route under the house. It's also a dual run, and both cables exhibit the same behavior. At this point I'm thinking that I may have run the cable under or over something that is causing these slight signal variations. So I've ordered a 1000' roll of high quality quad shielded RG6, and I'm going to rerun the cable using a different path under the house. Otherwise I'm not sure what I should be looking at. My questions would be;
1) Is it better to amp the incoming signal higher, and send it to a splitter? Or is my setup of splitter first to 2 drop amps ok? (BTW, is it ok to go about 30 feet with the CATV system input before amping it?)
2) Does a CATV system need to be grounded at every device, amp, splitter, where there's a ground screw? Or only once?
3) Do you need to do something special for runs of about 100 feet, like install grounding blocks or Ground Loop Isolators? (I did try installing 2 grounding blocks on both main long runs and it didn't change the signal levels at all)