What is the test to see if a cable TV jack is suppling a good signal, after
reconnecting my TV the picture quaility seems poor. Does adding a 2 way
splitter affect the signal? Thanks

"DanFXR" wrote in message
...
What is the test to see if a cable TV jack is suppling a good signal,
after reconnecting my TV the picture quaility seems poor. Does adding a 2
way splitter affect the signal? Thanks

Yes, adding a splitter can make a noticeable difference in those cases where
the signal was already marginal. In other cases where the signal is robust,
a splitter will not degrade the actual performance of the TV receiver.

"DanFXR" wrote in message
...
What is the test to see if a cable TV jack is suppling a good signal,
after
reconnecting my TV the picture quaility seems poor. Does adding a 2 way
splitter affect the signal? Thanks



A splitter cuts the signal amplitude in half, so if it was not strong enough
to begin with it can cause this problem. Sometimes an amplifier placed as
close to the cable entry to the house or antenna as possible can fix the
problem though.

"James Sweet" wrote in message
news:LMsWd.56503$uc.45478@trnddc03...

"DanFXR" wrote in message
...
What is the test to see if a cable TV jack is suppling a good signal,
after
reconnecting my TV the picture quaility seems poor. Does adding a 2 way
splitter affect the signal? Thanks



A splitter cuts the signal amplitude in half, so if it was not strong
enough
to begin with it can cause this problem. Sometimes an amplifier placed as
close to the cable entry to the house or antenna as possible can fix the
problem though.




Some splitters aren'e made for cable TV use. There are splitters that are
specified for VHF TV, VHF-UHF TV, Cable TV, Satellite TV, etc. The
differences are the frequency ranges that are covered by the splitter. Fer
instance, if your cable system provides up to channel 70, the frequency
range of the splitter should be a minimum of 50 Mhz to 500 Mhz. If your
cable system provides channels beyond that, your splitter should cover up to
900 MHz. Satellite splitters should cover 1500 MHz or more.
Check any splitters that the cable company installed. The frequency
coverage should be listed on the splitter label. Get one that matches the
coverage of that splitter.

--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!

"DanFXR" wrote in message
...
What is the test to see if a cable TV jack is suppling a good signal,
after
reconnecting my TV the picture quaility seems poor. Does adding a 2 way
splitter affect the signal?
Thanks

Can do. What happens if you take it out? You can get amplified splitters
from Radio Shack.

N

"James Sweet" bravely wrote to "All" (06 Mar 05 01:11:07)
--- on the heady topic of " Cable"

JS From: "James Sweet"
JS Xref: aeinews sci.electronics.repair:42392


JS "DanFXR" wrote in message
JS ...
What is the test to see if a cable TV jack is suppling a good signal,
JS after
reconnecting my TV the picture quaility seems poor. Does adding a 2 way
splitter affect the signal? Thanks

JS A splitter cuts the signal amplitude in half, so

Not the amplitude but the power. The amplitude is only reduced by
sqrt2 or -3dB, not by half.

A*s*i*m*o*v

.... :) What does that wire do? =8Q (oh!)

"Asimov" wrote in message
...
Not the amplitude but the power. The amplitude is only reduced by
sqrt2 or -3dB, not by half.

That's OK although 'power' would be a better word than amplitude, IMHO.

And when one is providing a technical answer to a question that appears to
be based on lack of appreciation of rather basic electronics knowledge,
whether one uses 'power' or 'amplitude' it does convey the basic idea of
significant loss of signal through a splitter; does it not?

Also that not all splitters are for the same use! It's rather like saying
'motor vehicle' and not defining whether you mean a motor cycle or a tractor
trailer truck!

Decibels are ten times the logarithmic ratio of two powers? See PS.

So more correctly might be to say "The power is reduced 3dB.".(Not reduced
by minus 3 dB! Two minuses making a +)

Voltage ratio would be reduced, as noted.
Using plain old Ohms Law to demonstrate;
i.e. voltage squared/resistance (or impedance) = power.

Voltage = 1 volt. Voltage squared = 1 and that divided by R = watts. (1/R)
Voltage reduced to 0.707 volts. Voltage squared = 0.5 and that divided by
the same R = watts times one half.
The logarithm of that power ratio i.e. 2 divided by 1 = 0.3 BELS. And that
is 3 deciBELS.
In this case it is a 'loss' of 3dB.

You can do it the other way;
Voltage increases by ratio of 1.414.
1.414 squared = 2
Twice means power ratio has doubled.
Logarithm of 2 is 0.3 so that is an 'increase' (or gain) of 0.3 Bels. That's
an increase of 3.0 deciBels.

Leastways that how I've always understood 'them dBs'! Plus 3 is twice the
power. Minus 3 is half the power.

Corrections and comments welcomed. Called Bels in honour of Alexander Graham
Bell; the Scotsman attributed with the invention of the telephone, in Canada
in 1876.

Thanks for reading. Terry

PS I've also gathered (and used in circuit transmission work) the reason for
using dBs is that one can add and subtract them to easily deduce the level
of, say any signal, at any point. Much easier than saying that certain
circuit has losses and gain characteristics of one eighth of one quarter,
multiplied by two and then reduced again to one quarter ....... etc.
With dBs that would be; minus 9, minus 6, plus 3, minus 6 = minus 6 (Did I
get that right?)
And that minus 6 dB means we end up with a signal of one quarter of the
original power?
And just to blather on further; if we started out with a reference test
signal of a certain standard level, typically "0 dBm (Note the 'm') from an
audio or RF signal generator, which was defined as one milliwatt reference
level, we would say that circuit has a loss of 6 dBs.

"Terry" wrote in message
. ..

....
Decibels are ten times the logarithmic ratio of two powers? See PS.

So more correctly might be to say "The power is reduced 3dB.".(Not reduced
by minus 3 dB! Two minuses making a +)
...

I recall hearing of a tech who was asked to look at a motel's cable system.
He found it was installed OK, but the installer used splitters throughout
instead of taps!! At the ends of the runs there wasn't much left BUT snow!

N

Terry wrote:

Voltage = 1 volt. Voltage squared = 1 and that divided by R = watts. (1/R)
Voltage reduced to 0.707 volts. Voltage squared = 0.5 and that divided by
the same R = watts times one half.
The logarithm of that power ratio i.e. 2 divided by 1 = 0.3 BELS. And that
is 3 deciBELS.
In this case it is a 'loss' of 3dB.

Don't forget that there is about .5 dB loss in the pair of
connectors, or .25 dB per input or output connector. I lab tested a lot
of different brands for a CATV company in the mid '80s and some two way
splitters had almost 4 dB insertion loss.

--
?

Michael A. Terrell
Central Florida