Which is it, RG59 or RG6?
in [Repair]
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From: Robert Macy on 5 Dec 2009 23:30 On Dec 5, 2:59 pm, Jeff Liebermann <je...(a)cruzio.com> 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 je...(a)cruzio.com > 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.
From: Joe Rooney on 6 Dec 2009 03:24 "mm" <NOPSAMmm2005(a)bigfoot.com> wrote in message news:tollh51ecqf64sh25unhdbsuilbns30l9n(a)4ax.com... > On Sat, 5 Dec 2009 15:52:16 -0600, "David" <someone(a)somewhere.com> > wrote: snip > dark colored lines. > > The end result is a picture that's pretty good, by 1970's over-the-air > standards, and the darks are darker now than they were in June, but > it's not smooth. I can live with this of course, for years if it > works out that way, but I like to fix things. > > > > >David Keep in mind a 3 way splitter has two 3.5db and one 7 db out. Joe Rooney
From: mm on 6 Dec 2009 12:03 On Sun, 6 Dec 2009 00:24:47 -0800, "Joe Rooney" <ikerooneyat(a)bigvalley.net> wrote: > >"mm" <NOPSAMmm2005(a)bigfoot.com> wrote in message >news:tollh51ecqf64sh25unhdbsuilbns30l9n(a)4ax.com... >> On Sat, 5 Dec 2009 15:52:16 -0600, "David" <someone(a)somewhere.com> >> wrote: > >snip > >> dark colored lines. >> >> The end result is a picture that's pretty good, by 1970's over-the-air >> standards, and the darks are darker now than they were in June, but >> it's not smooth. I can live with this of course, for years if it >> works out that way, but I like to fix things. >> >> >> >> >David > >Keep in mind a 3 way splitter has two 3.5db and one 7 db out. Aha. That would certainly account for a difference! I'll check later today. In fact, I'll take out the splitter and connect just the one giving me trouble. Thanks a lot. > >Joe Rooney > >
From: Jeff Liebermann on 6 Dec 2009 12:17 On Sun, 06 Dec 2009 12:03:52 -0500, mm <NOPSAMmm2005(a)bigfoot.com> wrote: >On Sun, 6 Dec 2009 00:24:47 -0800, "Joe Rooney" ><ikerooneyat(a)bigvalley.net> wrote: >>Keep in mind a 3 way splitter has two 3.5db and one 7 db out. Wrong. A splitter reduces the output by -3dB which is half the power. The extra -0.5dB loss is from losses in the bifilar wound xformer. If two of the ports each have half the input power, there's nothing in the budget left for the 3rd port. Googling for a typical 3 way splitter: <http://www.twacomm.com/catalog/model_CT413.htm?sid=1F79205DEA0D1B9FF1BF82ACDC4C33D2> I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes more sense. (Actually, it should be -7.0dB loss). A 3 port looks like a tree. It starts with a two port splitter, where one output is brought out for -3.5dB loss. The other port goes to yet another splitter, with again divides the output in half, for -7dB from each of the two ports. >Aha. That would certainly account for a difference! I'll check >later today. In fact, I'll take out the splitter and connect just >the one giving me trouble. Except that you said you're using 2 and 4 way splitters, which are far more common than a 3 way. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
From: Jeff Liebermann on 6 Dec 2009 12:30
On Sat, 5 Dec 2009 20:30:48 -0800 (PST), Robert Macy <macy(a)california.com> wrote: >Sorry, for jumping in here in the way of Jeff's capable hands, Grumble... >but >agree with honing in on potential bad connections in that old coax. There's a fairly easy way to detect bad connections. These invariably result in coax leakage, where the coax cable magically becomes an antenna. Find a portable TV receiver, tune it to CATV channels not OTA (over the air) channels, and sniff around with the portable antenna looking for leaks (actually called "ingress"). This is roughly what the CATV people do along the distribution cables using a pilot carrier. A broken shield, broken connector, and possbibly a missing termination, should all show up as excessive leakage. Personally, I prefer visual inspection, a TDR (time domain reflectometer), signal level measurements, or just a pre-emptive replacement. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |