A Broadband and ADSL forum. BroadbandBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » BroadbandBanter forum » Broadband, ADSL & VOIP newsgroups » Cable Modems
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Cable Splitting (-7db vs. -3.5db)



 
 
Thread Tools Display Modes
  #1  
Old March 25th 11, 01:06 AM posted to comp.dcom.modems.cable
PostMaster
external usenet poster
 
Posts: 2
Default Cable Splitting (-7db vs. -3.5db)

When my cable was originally installed they hooked it up to a 3 way
splitter. 2 of the outputs are listed as -7db (1 going to analog tv
in
bedroom and the other -7db to modem [30mb service at that time]. The
-3.5db to the HDTV in living room. I have my doubts that it was done
correctly to begin with.

I have a couple of different questions on the subject. Which is the
stronger signal and how would it be best to break it down to 4
outputs? If I split a -3.5db would it make two -7db or would
splitting
-7db make two -3.5db? Which is stronger? What is sufficient? I know
what a decibel is relating to sound but I have no idea how it relates
to data transfer speed. If someone could briefly explain the
difference.

I want most of my bandwidth to go to my modem and my HDbox in living
room. The other 2 outputs I'm just using 2-99ch analog. As it stands
now my internet connection doesn't seem to perform as well as it
could
and I get some occasional freezing on my HD signal. Everything in my
hard wired network checks out fine. I have checked all connections
inside and I am using high quality cable. I also had the cable
company
come out and check the line outside and they even installed a new
lock
box. I am also concidering an inline booster, or even a powered one
if
it would make a noticable difference.

If there is anyone with an electronics degree out there that could
show me the light I would be most grateful.
I basically just want to make sure I'm doing everything from the wall
to the devices as efficiently as I can possibly do it.
thanks,
pm
Ads
  #2  
Old March 26th 11, 07:03 AM posted to comp.dcom.modems.cable
PostMaster
external usenet poster
 
Posts: 2
Default Cable Splitting (-7db vs. -3.5db)

On Mar 24, 10:08*pm, Bill M. wrote:
On Thu, 24 Mar 2011 18:06:52 -0700 (PDT), PostMaster





wrote:
When my cable was originally installed they hooked it up to a 3 way
splitter. 2 of the outputs are listed as -7db (1 going to analog tv
in
bedroom and the other -7db to modem [30mb service at that time]. The
-3.5db to the HDTV in living room. *I have my doubts that it was done
correctly to begin with.


I have a couple of different questions on the subject. Which is the
stronger signal and how would it be best to break it down to 4
outputs? If I split a -3.5db would it make two -7db or would
splitting
-7db make two -3.5db? Which is stronger? What is sufficient? I know
what a decibel is relating to sound but I have no idea how it relates
to data transfer speed. If someone could briefly explain the
difference.


Since these are negative numbers, (referenced to 0dBmV), if you split
a -3.5dB signal in half, each half is approximately -7dB.

TV's are usually pretty forgiving of signal strength and are able to
work over a wide range. Some TV's have an on-screen signal strength
meter, sometimes available via the Info button on the remote. Those
meters aren't calibrated or standardized in any way, but they can give
you a rough idea of where your signal levels stand.

Cable modems, on the other hand, are usually specified to work over a
range of +15db to -15db, and because signal levels can fluctuate over
time due to various external factors, some people like to play it a
bit safer and want their cable modem to work within a range of +10dB
to -10db.

There is no relationship between signal strength and data transfer
speed, assuming the modem is working with an acceptable signal. Many
modems have an internal web server that will show you, among other
things, your Upstream and Downstream signal levels and your Downstream
Signal-to-Noise Ratio. Try browsing tohttp://192.168.100.1

You might want to draw a map of your entire cable network, showing the
incoming cable, each splitter (and its effect on the signal), ending
with each TV or modem. For planning purposes, assume the incoming
cable has a signal strength of 0dB, then just subtract 3.5dB for each
leg of a 2-way splitter or subtract 7dB for each leg of a 4-way
splitter. 3-way splitters can either be balanced, (the same amount of
loss on each leg), or unbalanced, (-3.5dB on one leg and -7dB on the
other two legs). The unbalanced type is more common, and is
essentially a 2-way splitter with one output leg feeding into a second
2-way splitter. Likewise, a 4-way splitter can be thought of as a
2-way splitter with each leg feeding an additional 2-way splitter.

Once you've drawn the map and have taken all splitters, amps (if
applicable), and your cable modem's signal level into consideration,
you're ready to decide if changes need to be made. Changes could be as
simple as rearranging your existing splitters, combining multiple
splitters into fewer splitters, asking the cable company to adjust the
level of your incoming signal, or as a last resort, adding a 'drop
amp'.

--
Bill


You pretty much gave me all the info I need to achieve my goal.
Much Thanks.
PM
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Random disconnections from a Terayon TJ715x cable modem? Ant[_4_] Cable Modems 78 October 20th 08 10:51 AM
Connecting two internal networks to internet via cable modem [email protected] Cable Modems 0 December 3rd 05 08:38 AM
Comcast cable modem problem [email protected] Cable Modems 6 April 20th 05 05:56 AM
can two PC's connect with optimum? Karen Cable Modems 11 October 22nd 04 04:22 PM
3-way splitter with cable modem and digital cable Scott Cable Modems 1 June 4th 04 05:29 PM


All times are GMT +1. The time now is 08:13 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2004-2014 BroadbandBanter.
The comments are property of their posters.