In alt.home.repair on Tue, 19 Jul 2005 00:11:28 -0700 Eric
posted:
meirman wrote:
In alt.home.repair on Mon, 18 Jul 2005 22:27:34 -0700 Eric
posted:
What does it take to measure the Cable TV signal strength at the box?
ie: how do you do it, and what are good, bad, and poor values?
Thanks
Eric
An oscilloscope would be good.
I would take a tv out there and see what sort of picture you get.
I would be especially good to use one that gets a bad picture when
connected to the cable inside.
I would connect a known good 9 or 12 inch tv inside to the same place
I was getting a bad picture inside and a) see if that tv got a good
picture where your bigger tv is providing a bad one; b) if it got a
good one, the primary problem might be your regular tv (but don't jump
to conclusions.) c) If it didn't get a good picture, I'd take the
little one outside, to the cable box you refer to above (you are
talking about outside, aren't you?), and see what kind of picture it
got there. It's a lot easier to carry a little tv** than a big one.
blah, blah, blah. You get the general idea.
**Of course small screen tvs normally give better pictures than large
screens do. You'll have to keep that in mind. Or use a bigger one if
all your initial testing is inconclusive.
I would also buy a 50 or 100 foot roll of coaxial cable, with ends --
I forget the name of tv cable -- and a female to female coaxial
connector, and connect that to the cable outside, and the other end to
the tv you're having trouble with inside. Bypass all the interior
wires, boxes, and tuners. See how the picture is now. Then connect
it to the box closest to that tv and check again.
How many splitters do you have inside? How many tv's connected to the
cable? After a certain number, above 2 or 3?, you need a cable
amplifier or your signal gets weak. Although I don't like Radio
Shack, I'm using two of theirs for the seven tv's I feed directly out
of my vcr.
The amps have input and output and an AC cord but no controls. At
least one amp only has 2 outputs and was very cheap. The other one is
buried under shoes and things in my closet and I haven't seen it for
10 or 15 years. But it works fine.
Length of cable isn't a problem in my experience. 22 years ago when I
asked the cable guy to put the channel selecting box in the closet, 5
feet away, instead of next to the tv, he expressed uncertainty that it
would work well at such a distance. It worked fine. Later, I had a
cable going from the same box down 2 levels through the floors to the
basement, 50 feet up to front of the house, 50 feet back and 50 feet
up again**, and then up one level through the wall, and the picture
was just as good as in the bedroom. And the guy made it sound like 5
feet were difficult.
**For some reason I couldn't cut the wire until I did something else,
I forget now. Something to do with going along inside the basement
ceiling.
Meirman
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The picture i have is fine, but I have another problem which could possibly
be attributed to marginal signal. I have a DVR. Certain channels dont
record well, for example, if i record the Science channel programs , then
when i play it back there are drop outs and lost audio, picture breakup etc
it comes and goes in the recording. Other channels record just fine. Just
plain TV watching is good too. I just had this installed by comcast in June
and its been a problem since day 1. Do i have a bad DVR? a weak signal?
maybe in record mode it requires a slightly higher strength signal? I'm
baffled.
Eric
You can use most of the advice in my first post to analyse the DVR.
You can also take it the home of someone who can record those
channels, on a vcr or dvr, and see how your dvr works there. And
maybe vice versa.
And you can discuss it with Comcset.
Meirman
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