On Sat, 05 Dec 2009 14:59:33 -0800, Jeff Liebermann
wrote:

On Sat, 05 Dec 2009 16:44:42 -0500, mm
wrote:

I gather from posts here that RG6 is better than RG59, is that right?

Yep. RG-6/u is generally better for most everything.

Could the use of of RG59, 33 feet, for at least one tv be responsible
for my bad reception on that tv?

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

Also, if you have a scope and are interested in building a TDR (time
domain reflectometer), you can test the cable.
http://en.wikipedia.org/wiki/Time-domain_reflectometer
http://www.epanorama.net/circuits/tdr.html

I think you had the right idea the first time, substitution.

Did they have RG-6 25 or 30 years ago?

Oh yes. It was in the original military "radio guide" MIL-HDBK-216
from WWII. The "6" means page 6 of the guide.

Very interesting.

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**.

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.

Will do.

Do you think replacing the RG59 with RG6 will get me the perfect
picture other sets get?

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.

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.

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.

It'll probably be 10 more years before I have a digital tv in this
room.

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.

Holdit. Any one of these can be the problem. That includes
amplifiers and splitters with unterminated outputs.

I don't have any unterminated outputs.

First, you don't
really need all those amplifiers.

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.**

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 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.

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.

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.

Try replacing the amps with an ordinary 2
way or 4 way splitter and see if it magically fixes the problem. Also,

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.

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.

Would an additional signal amp
at the start of the RG-59 also give me perfect or at least improved
reception?

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.

But every amp supplies signal to more than one tv, and only this one
tv has a problem.

**(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.)

You lost me. What does this have to do with anything? Draw you

Sorry. Not important. Never mind.

topology (wiring) and post it somewhere. Don't forget to include some
numbers.

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.

7 tvs are connected, an eighth used to be.