I gather from posts here that RG6 is better than RG59, is that right?
Could the use of of RG59, 33 feet, for at least one tv be responsible for my bad reception on that tv?
I'm using co-ax for distributing tv from my DVDR to TVs throughout the house. (The DVDR tunes in the over-the-air digital signal and I have an RF modulator to change the DVDR output to analog. I did the wiring to the tvs 25 years ago, and I used left-over and scrap co-ax, so the co-ax is older than 25 years. Did they have RG-6 25 or 30 years ago? I didn't pay attention then so I don't know what most of it is, but the 33 foot piece going to this one tv is RMS Electonics Inc. 59/U.
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**.
Do you think replacing the RG59 with RG6 will get me the perfect picture other sets get? I didn't use home-runs, just splitters and every two splitters a signal amp, a total of three signal amps, one with 2 or 4 outputs, and two with 2. Would an additional signal amp at the start of the RG-59 also give me perfect or at least improved reception?
**(But the set-top box isn't connected to the main antenna and doesn't get several stations I watch, nor will it play what is recorded on the DVDR.)
Yes RG6 existed 25 years ago. You have something else wrong. The difference in loss between 33 feet of RG59 vs. RG6 is negligible at VHF and at most a few dB at the higher UHF frequencies. What else is in that 33 foot span?
BTW, I'm using an A/B switch now. I had this problem when I was connected directly, but is there any point in getting a gold-plated A/B switch?
It's in the attic. About two feet away are two four-inch galvanized sheet metal tubes/ducts that the bathroom fans use to blow air out of the bathroom to the crest of the roof, but the fans are never on. The cable doesn't go by any electric wires because the bedrooms were built without ceiling lights. The bathroom ceiling light is maybe only two feet away but it makes no difference if the light is on or not.
There's a 1 to 3 splitter, with one output going to another tv which has a perfect picture, one has a terminator resistor designed for this purpose (in an F connector), and the other output goes to the problem tv.
The picture even from analog was perfect on most stations until analog ended, and afaicr that was exactly when this tv picture got grainy. But for fear this was a coincidence, I waited to ask this queestion until I had a different tv to use here. I put that in today, and it too has a grainy picture, even though when it was connected in the basement, it had a smooth, perfect picture. Well, being grainy is the only thing that's not perfect about it, afaic.
Besides being grainy, or maybe this is part of what I'm calling graininess, the problem picture has a lot of teeny tiny white dots sometimes just scattered in the picture and sometimes arrayed in dim horizontal and vertical lines, about 5 lines horizontal. and 7 lines vertical. The lines are not that straight and the vert lines move left and right a little bit and the horiz lines up and down a little bit. There also seem to be dots of other colors and sometimes jaggedy 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.
Yep. RG-6/u is generally better for most everything.
If the coax cable is in good shape, hasn't been eaten by rats, mice, squirrels, kids, vacuum cleaners, etc. and has properly attached connectors, then there's almost no difference in performance between RG-59 and RG-6/u. In my limited experience, lousy connector crimping and mouse eaten cables are the usual culprits.
You must enjoy low quality video. It appears that you're also using that derrangement to move audio, so the analog video is really NTSC encoded with an approximately 4MHz maximum bandwidth. If all you have is an analog TV, that's fine and will work, but if you're watching this on a digital capable TV, it's wasting the capabilities of the TV.
Incidentally, thanks for leaving out all the make and model numbers, as well as most of the numbers. That adds some credibility to my guess work. If you want help with your SPECIFIC problem, it helps to supply some specifics as to what manner or video problem you're seeing and what manner of hardware you have to work with.
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.
Also, if you have a scope and are interested in building a TDR (time domain reflectometer), you can test the cable.
Oh yes. It was in the original military "radio guide" MIL-HDBK-216 from WWII. The "6" means page 6 of the guide.
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.
Dunno. I would find the cause of the problem before ripping out the cable. However, if it's easy to get to and doesn't make too big a mess, it's worth a try. Either RG-59 or RG-6/u will work as you're only using it on Channel 2 or 3 with the RF modulator.
However, if you were going to shovel the entired TV spectrum, from VHF to the top of UHF through the cable, as you will if replace your analog TV with a DTV, then I would use RG-6/u.
Holdit. Any one of these can be the problem. That includes amplifiers and splitters with unterminated outputs. First, you don't really need all those amplifiers. Most TV's can easily handle one or two 2 or 4 way splitters, without an amplifier. However, I have no clue how much RF output your unspecified RF modulator belches or what your amplfiers are doing. I also can't guess your topology (wiring layout). My guess(tm) is that you have too many amplifiers or one of them is unplugged or dead. Try replacing the amps with an ordinary 2 way or 4 way splitter and see if it magically fixes the problem. Also, if you don't have a CATV signal level meter, walk the TV around to the various amps until the bad section or amplifier is found. If you have any unterminated outputs, kindly terminate them with a 75 ohm terminator.
No. You already have too many amplifiers. You'll do better by getting rid of amps or at least finding which one is the culprit. It might still be the coax, but I'm more inclined to guess(tm) that one of the amps if fried or sick.
You lost me. What does this have to do with anything? Draw you topology (wiring) and post it somewhere. Don't forget to include some numbers.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Try connecting each set directly by replacing the splitters with thru connectors and see if they all work ok. This will require that you undo and redo a bunch of connections as you check out eachset and associated cables,, but it is the only way to be sure that your basic components are good. I agree with other posters that bad crimp connectios are a frequent problem. A little corrosion aftrer 25 years may make the contact between the outer shield/aluminum ground wire to the connector outer housing intermittent and that can do wonderous things. If the output of the dvr is of typical levels, it should easily drive another set 30 feet away. I have a 3-way splitter on the output of my cable box and it drives the nearby tv as well as two other sets 30 feet away, using a 1-3 splitter, with perfect pictures.
On Dec 5, 2:59=A0pm, Jeff Liebermann wrote: ...snip...
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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.
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.
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:
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.
Except that you said you're using 2 and 4 way splitters, which are far more common than a 3 way.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
It says "3 way-loss 2 at 6.5 DB, 1 at 3.5 DB, 20 DB isolation DC passive"
What does DC passive mean? Will it transmit DC power to an amplified antenna, for example?
I did have a 4-way in there, but later on the slim possibility something was wrong with the splitter, I switched and the next one I found in my drawer was 3-way. Of course the problem pre-dates the
3-way, but I jumped to the conclusion that the 4 way might have had something like this too.
I realize now I shouldn't have used a 4=way since i never had plans to use more than 3 of them, but 25 years ago, I iddn't know they made
Thanks. I will check both those things next time I"m in the attic, some time this week. No problems in the part that shows.
No, I can't afford any digital stuff. I've only bought one TV in the last 37 years, but I get more than 50 of them at yard sales or out of the trash. Some work when I get them, some I can fix, some I can't.
So I have to wait until I find some digital stuff cheap, and that's been slowed down because as of a month ago the county trash collection will no longer pick up tvs. People have to arrange to take them to 3 locations in the county. For many, the closest is 10 miles away.
I should have mentioned in the first post that today I tried another tv, and it had the same problem with the picture. OTOH, a second tv connected to the same splitter, and also using a different splitter, displays a perfect picture.
The two tvs with bad pictures in this room were a 12" Zenith 5 or 10 or 20 years old and 12" Magnavox with a VCR in the same age range.
I can give you model numbers if you want. But since they both give perfect pictures when the signal is from the set-top box on top of the tv, I didn't think the tv was the issue.
I should have thought of that. I can run it through the trap door to the attic. No need to remove the stuff that is there. My long pieces of coax are buried in the basement This will have to go back on the back burner until then.
I think you had the right idea the first time, substitution.
Very interesting.
Will do.
The attic gets fuller and fuller, mostly empty boxes, and more insulation, and I'm 25 years older. It still woudln't be so hard to replace the cable, if the substitute works right.
But it would be a lot easier, i realize now, to bypass the splitter and connect the problem tv directly. Or to bypass the cable and run another one temporarily outside the wall, not in it.
It'll probably be 10 more years before I have a digital tv in this room.
I don't have any unterminated outputs.
I take it back. Now I think I only have two amplifiers. For years I was sure that I had 3, maybe I do but I can't figure out where the third one would be. Please forgive me. I put some of this stuff in
26 years ago and the rest 24 or 25 years ago. I plugged the amps in and haven't had to do a thing since. At least until this fall. 24 years with no maintenance needed is pretty good.
Details about tv hookup below.**
I certainly don't know, but it's conceivable that the RF modulator puts out much more than the various VCR's I used did, but all I did about 18 months ago was replace a mediocre VCR with a Philips DVDR3576H DVD recorder with 160 Gig hard drive, and add a RF modulator that cost about 18 dollars on Amazon, and everything worked and I didn't verify any of the outlying circuitry or tvs. I'm 99% sure even this tv gave no problems then , 18 months ago, and only gave problems last June when the analog stations went away. I had been watching analog for a whole year even after I had a digital tuner, because channel surfing is much quicker in analog.
If one were unplugged, at least one other tv would have little or no picture. I think. Since every amp suplies signal to at least two tv's. But after I try substituting the cable, I will look again at the main amp.
Not likely, because I didn't put the amp in until the signal was too weak and the picture was washed out. Only if the RF modulator puts out a substantially stronger signal than the first VCR did. But I appreciate the suggestion and will try it if all else fails.
But every amp supplies signal to more than one tv, and only this one tv has a problem.
Sorry. Not important. Never mind.
I'm good at neither drawing nor posting. Last time I tried posting, it was a time-consuming failure. But I think I can describe it clearly.
**I was running 8 tvs but now I'm running 7 off of the DVDR, formerly the VCR, and I never put in an amplifier until I put in another splitter, ran co-ax to another room and connected a tv and saw that the picture was washed out.
The VCR, now DVDR, is in my bedroom. (I used to have Comcast cable that went to the VCR.) The output from the DVDR goes to the closet where there is a 4 way amplifier, with one output terminated, one to the tv right there in that bedrroom, one to the attic (A), and one to the first floor & basement (B).
(A) goes into the attic and 20 feet away splits 3 ways, one terminated***, one to the tv in the bathrom which has a perfect picture, and one to the tv in the office/spare bedroom, with the problem picture. ***When I spent more time in the attic, I had a tv stored up there, that I watched, and it used the now-terminated output.
(B) goes to the first floor and a two way splitter, one output to the living-room tv, and one output to the basement. In the basement family room is a another amplifier with two outputs, one output to the family room tv and one to the laundry room.
In the laundry room is another splitter, one output to the laundry room tv (I needed a place to store an extra tv anyhow, so I might as well connect it) and one output upstairs to the kitchen.
When I first got cable tv -- I don't have it anymore --, the guy ran the cable in through the floor of the close, which overhangs the first floor. The cable box connected to a channel control dial via a cable, no infra-red, and I told him I wanted to keep the box in the closet, out of my way.
He said he wasnt' sure if the tv could that far from the box. The tv was about 6 feet away.
Later when I connected the first remote tv and was running the co-ax through the basement ceiling, so for some reason it was 3 times as long as it would be when I was done, it was about 120 feet and it still worked fine, but he thought 6 might be too much. (I didnt' get the slightest impression he was looking for a tip for him to make a wire 7 feet long, but maybe I'm dense and that's what he wanted?? That didn't occur to me until just now.)
Yep. DC passive means that there is DC continuity between the ports.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Not all of them. If you know where to look, you can find three way splitters with -5 dB at each port. They were in use in CATV in the early -80s. I kept a small stock of them at the United Video system in Delhi Township (Cincinatti, Ohio) for installs where the standard version wouldn't work.
Part of the extra .5 dB loss is in the cast aluminum 'F' connectors. I ran Q. A. I ran tests on hundreds of samples to qualify them for our MSO to purchase the best quality we could find. We bought splitters by the thousands, and coax by the pallet
Also, eight way splitters are listed at -10 dB, not 10.5.
Yes. Some splitters will pass DC, usually only to one port.
The 20 dB isolation means that the return loss is more than 20 dB. This is to prevent the local oscillator from one TV causing interference to another TV. I was the engineer at a CATV system with over 10,000 active drops. There are hundreds of myths and half truths about the hardware used for CATV systems.
An ideal splitter would be 3 dB, 6 db, 9 db etc., but connector losses, and to a smaller extent, core losses in the broadband transformers add the fractional losses.
Cable installers are first tier techs. They aren't trained to think, or troubleshoot. The standard cable between the TV and the converter was three feet, because that worked with 99% of the TVs in use.
You should see the calculations needed to design a trunkline or feeder, or even worse, to interconnect two CATV systems. I wrote software in the mid '80s to allow me to select the hardline by size and vendor, along with the passives. Our designs called for a minimum of
+10 dB at the tap, but to minimize the number of trunk or bridger amplifiers. You used a strand map to get accurate distances to calculate the cable losses, then selected the tap required. That added a block of loss to the feeder. Each calculation was based on the ones before it.
Ingression is external signals getting into the CATV plant. You are describing radiation' where the signal is lost to being radiated from the outer conductor, due to poor connections. It is monitored on a continuous basis on most cable systems using 'Sniffer' or other brands of monitoring equipment. While the signal is on the video carrier frequency, it is FM modulated with annoying audio to make it easy to identify.
Those are OK if you can shut a system down for repairs. Poor connections in the trunkline can be detected by reading the voltage drop between the coax and the amplifier housing, splice block or any other splice in any powered cable. 60 volts modified sine wave AC @ 30 amps from a CVT doesn't tolerate much resistance without causing hum modulation or burning up a connector.
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