On Dec 5, 2:59*pm, Jeff Liebermann wrote:
....snip...
Ok, the coax is suspect. *This is easier to troubleshoot by
substitution. *Find a 50ft piece of decent 75 ohm coax cable. *Run it
in place of the suspected 33ft piece. *If it magically fixes the
problem, your old coax is history.
....snip...
Everything was fine until the digital conversion, and now this tv that
I watch a lot shows a grainy picture. * All the other tvs have great
pictures, and even for this one, when I supply a signal directly from
a set-top digital converter box, only 3 feet of cable, it shows a
perfect picture**.

I guess "grainy" means you're getting a weak signal. *Well, drag one
of your other TV's over to this location and see if it's a consistent
problem. *If the 2nd TV is also "grainy", then you probably have a low
signal level for some reason. *Again, it can be the cable or the
connectors. *A broken shield connection will still deliver a signal,
but at somewhat lower level. *Also, substitute the coax with a known
good one as I previously suggested.

....snip...
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

Sorry, for jumping in here in the way of Jeff's capable hands, but
agree with honing in on potential bad connections in that old coax.
Plus, the description of the received signal reminds me of when I had
to use an amplifier to overcome the loss from attempting to use a
splitter, only to find that some strong station was doing?? whatever
to create an overlay image on top of my viewing. Since the crystals
are so close, frame images drift over the top of each other. Looks
like the overlay dot patterns like OP described. For me, was
confirmed when one day I could actually read the call letters of the
'offending' overlay.

Also, OP said this started happening when DTV took over. That day a
lot of broadcast stations started switching their power signals
around. Even as late as October 31, they were still being shifted.
Perhaps, the band change showed up mixing, or affecting the AGC

Background of my experience with this: I added a security camera to
our home viewing. Simply popping to unused channel and I could see
who was at the front door. Sadly, I learned that RF Modulators
produce such a weak signal that I had to add an amplifier to make up
for a single one to four splitter stage. And then the problem of the
dynamic range of antenna reception reared its ugly head. And mixing
in the amp, and ad nauseum.