On Dec 5, 4:59*pm, 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.
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.
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 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.
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
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.
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.
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. *
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.
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. *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.
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 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
topology (wiring) and post it somewhere. *Don't forget to include some
numbers.
--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://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.