I've been skulking around here for years, but this will be my first post as a registered user as I need some help!

In my bedroom, I have a Scientific Atlanta HD-DVR (Explorer 8240) connected first to a Monoprice 5x1 HDMI switch (r 2.1) and then to an Akai LCT42Z6TM 42" 1080P LCD. The connection is made from the cable wall jack to a MonsterPower surge protector and then to the STB.

For a few weeks now, I have been experiencing what I can best describe as inteference. Horizontal white lines flicker accross the picture. Each set appears for no more than a half second and then move to a different location. The problem does eventually seem to correct itself but is very annoying nontheless as it can take up to 5 minutes after the STB is turned on.

I also have a PS3 and Sony upconverting DVD player hooked up to the HDMI switch and have had no trouble with either of those items (since having a defective HDMI switch replaced several weeks ago.) This lead me to believe that it was not the switch or the HDMI connection on the TV but, to be sure, I connected the STB via component cables. Unfortunately, the interference continued. This, I feel, safely rules out the switch being an issue.

I also tried a different coaxial cable but the problem was not rectified. Of course, I have tried rebooting the system and contacting Cox tech support.

I have noted that my QAM signal strength is low @ this jack (-12) and would simply be willing to lable this a signal strength proble were it not for one inconsistency: When the problem occurs, the lines are also visible over the on-screen menus rather than just the broadcast picture.

Do you folks feel that this IS an issue with signal strength, that my STB is screwed up, or that there is some bizarre error with my TV?

Thanks in advance!!! :)

Update:
I replaced the Coax cable I had hooked to the walljack with a monster cable coax that I had lying around and performed the signal strength teast agian. My signal strength is now an acceptable -8 to -6 but I am still experiencing the horizantal bar interference.
Any ideas???

For a few weeks now, I have been experiencing what I can best describe as inteference. Horizontal white lines flicker accross the picture. Each set appears for no more than a half second and then move to a different location. The problem does eventually seem to correct itself but is very annoying nontheless as it can take up to 5 minutes after the STB is turned on.
If the horizontal lines scroll up or down the picture, that is a classic symptom of ground loop. Ground loop occurs when one of the pieces of A/V gear or an input line is not grounded to the same reference ground. Do the lines go away when you disconnect the co-axial cable line? A common cause of ground loop is a poorly or ungrounded RF co-axial cable line. A search for ground loop should turn up threads on how to fix it.

Please accept my apologies if I misunderstand you, and thank you for your help.
I have all of my components as well as my coaxial line connected to a monster power surge protector which is then connected to a grounded power outlet. As such, I assume that it should be properly grounded. Is there something else that I could be missing?
As far as the horizontal lines go, I don't believe that they scroll as you describe. (I have seen this condition before in the past.) Instead they are white line that appear, several at a time, at random spots on the screen. None stay for long before they disappear and reappear elsewhere on the screen.

I'd try a hookup bypassing the Monster device with the coax. It's often better to avoid passive or active routing of high-frequency signals when possible. Another option is trying YPbPr hookups to see if it's a HDMI glitch. -- John

I've already tried connecting via component and bypassing the surge protector. Results are the same. :confused: