A question from a lay person. I'm looking for information on what kind
of CATV splitter to buy. I have Time-Warner analog CATV and don't use
any cable box. All my devices use coaxial RF cable as input. Here's my
setup...

Cable comes into my house's outside junction box into a 4-way splitter
with each output saying 7dB (whatever that means), then goes to four
rooms.

Room 1: Bedroom without any TV. Coax not terminated.

Room 2: Office with cable modem and TV. Cable company used a 2-way
splitter with each output saying 3.5dB.

Room 3: Bedroom with a TV.

Room 4: My main media room. Here's where I need the right coax splitter.
I currently have a 2-way splitter connected to a VCR and a TiVo. I'd
like to add a DVD recorder with a cable-ready tuner. All 3 devices would
have coaxial RF cable input.

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4. I saw such a splitter at Radio Shack. Is there a
better brand?

2. Should I terminate the cable in the unused Room 1?


Thanks for any suggestions.

Jerry

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4. I saw such a splitter at Radio Shack. Is there a
better brand?
*********************
Yes & no...if the splitter is a 1 gig splitter, it'll work. Don't use the
900mhz splitters...they'll work...so so...but you'll get better signal
through the 1 gig splitter, and they are not expensive...I get them at Home
Despots...about $5...can't remember if they are Ideal or RCA branded...you
will probably not need any signal amps...unless your really working with a
bad cable company. They take special care to boost their signal throughout
their network, and really try hard (in my area with Comcast) to pump good
signal to their users.
*********************
2. Should I terminate the cable in the unused Room 1?
*********************
Always terminate unused coax ends tied to the distribution network.
*********************


Rich

That 7db label means that the splitter is reducing the signal by 7db. As
you add more splitters down the line you further reduce the signal. Try
the 4 port splitter and see how your picture looks. At that point you'll
have a 14db signal loss but if the picture is good that's all the
counts. If it's grainy you may need to use a 4 port drop amp. You can
get good ones (Electrohome, Scientific Atlanta, etc) on ebay for about
$20.

From:Jerry


A question from a lay person. I'm looking for information on what kind
of CATV splitter to buy. I have Time-Warner analog CATV and don't use
any cable box. All my devices use coaxial RF cable as input. Here's my
setup...

Cable comes into my house's outside junction box into a 4-way splitter
with each output saying 7dB (whatever that means), then goes to four
rooms.

Room 1: Bedroom without any TV. Coax not terminated.

Room 2: Office with cable modem and TV. Cable company used a 2-way
splitter with each output saying 3.5dB.

Room 3: Bedroom with a TV.

Room 4: My main media room. Here's where I need the right coax
splitter. I currently have a 2-way splitter connected to a VCR and a
TiVo. I'd like to add a DVD recorder with a cable-ready tuner. All 3
devices would have coaxial RF cable input.

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for
future expansion in Room 4. I saw such a splitter at Radio Shack. Is
there a better brand?

2. Should I terminate the cable in the unused Room 1?


Thanks for any suggestions.

Jerry

On Wed, 03 Nov 2004 10:04:53 GMT, Jerry wrote:
1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4. I saw such a splitter at Radio Shack. Is there a
better brand?

Hi Jerry,

Sounds fine. Better brand? Probably not (in other words, same
chinese product with a different label).

2. Should I terminate the cable in the unused Room 1?

Only if your picture appears to be fuzzy or distorted; however, it is
a simple matter to perform and doing it tends toward a better
solution. If you do, you should also terminate the unused splitter
output too.

73's
Richard Clark, KB7QHC

On Wed, 03 Nov 2004 10:04:53 GMT, Jerry wrote:
Cable comes into my house's outside junction box into a 4-way splitter
with each output saying 7dB (whatever that means), then goes to four
rooms.

Usually that "7dB" means the output has 7dB less signal strength than
the input. In this context, 3dB down means one-half (1/2) the signal,
so 7dB means 1dB less than 1/4 the signal. In an ideal 4-way splitter,
each output would have 1/4 the signal, so your splitter has some 1db
additional real-world loss (expected, and 1db is OK, 1.5db is bad).

To overcome loss and signal division, you might need to add a
distribution amplifier before the first splitter in the junction box.
Usually a cable company will install one, especially if using a cable
modem. This is usually a box with a cable in, cable out, and a cable
connected to a power adapter. Sometimes you can get an amplifier
combined with a splitter. I don't like those.

In addition to a loss specification, the bandwidth of the splitter (or
amplifier) is often specified. For satellite and digital cable, and my
preference in all installs, are splitters with a bandwidth up to at
least 1ghz.

Room 1: Bedroom without any TV. Coax not terminated.

Room 2: Office with cable modem and TV. Cable company used a 2-way
splitter with each output saying 3.5dB.

That splitter shows that each output gets a little less than 1/2 the
input signal, or less than 1/8 of the original signal (1/4 divided by
2).

Room 3: Bedroom with a TV.

Room 4: My main media room. Here's where I need the right coax splitter.
I currently have a 2-way splitter connected to a VCR and a TiVo. I'd
like to add a DVD recorder with a cable-ready tuner. All 3 devices would
have coaxial RF cable input.

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4.

A 4-way splitter would cut signal strength in half to each of the
devices currently connected to the 2-way (from 1/8 to 1/16).

A 3-way splitter (or two of them) would give a slightly stronger signal
if used instead of the four-ways. Splitters are also available in 6-way
and on up. Just a bit harder to find. I've had good results with
the high-grade (low loss, wide bandwidth) splitters from MCM
Electronics.

Can you run any additional coax from the junction box to the various
rooms? My preference would be to disconnect (at the junction box) Room
1 (since it isn't used) and run that output via a new line to Room 4.

Now with 1/2 the available signal in room 4, you can run 1/8 1/8 1/4 to
three devices, or add a 2-way splitter and run 1/8 1/8 1/8 1/8 to four.
Or you could replace the splitter in the junction box with a bigger
number of outputs and that way everything would have equal signal.

If you ever have cable modem problems with signal strength, you could
either run a second line to room 2 (one for each device) or else use a
2-way splitter at the junction box before the 4-way, connecting the
4-way to one output (1/2 the signal) and the room 2 line to the other
(1/2 the signal to room 2, where it gets split so each device gets 1/4
instead of the current 1/8).

2. Should I terminate the cable in the unused Room 1?

In theory, all unused outputs should be terminated. It might or might
not make any noticable difference.

sdb

In article ,
Jerry wrote:

A question from a lay person. I'm looking for information on what kind
of CATV splitter to buy. I have Time-Warner analog CATV and don't use
any cable box. All my devices use coaxial RF cable as input. Here's my
setup...

Cable comes into my house's outside junction box into a 4-way splitter
with each output saying 7dB (whatever that means), then goes to four
rooms.

That means that the RF signal level at each output port is 7 dB below
the level being fed into the input. That's not too bad - a perfectly
lossless 4-port splitter would divide the power four ways, resulting
in an output level at each port which was 6 dB below the input level.
This splitter has 1 dB of additional loss.


Room 1: Bedroom without any TV. Coax not terminated.

Room 2: Office with cable modem and TV. Cable company used a 2-way
splitter with each output saying 3.5dB.

Again, that's not too bad - 3 dB of reduction per port (50% of the
power going each way), plus an additional .5 dB of loss in line with
each port.

This means that your TV and cable modem are seeing signal levels 10.5
dB below the level that your cable company is feeding your house.

Room 3: Bedroom with a TV.

Room 4: My main media room. Here's where I need the right coax splitter.
I currently have a 2-way splitter connected to a VCR and a TiVo. I'd
like to add a DVD recorder with a cable-ready tuner. All 3 devices would
have coaxial RF cable input.

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4. I saw such a splitter at Radio Shack. Is there a
better brand?

You could do that. You'll be wasting some of the RF power fed to that
room, into the termination resistor on the fourth port.

Or, you could daisy-chain an additional 3.5 dB splitter off of one of
the two ports on the existing two-way splitter. This approach will
give you three outputs, two of which have lower RF levels than the
third. Use the third port (the one coming out of the first splitter)
to feed whichever device seems to need the strongest signal for a
decent picture.

2. Should I terminate the cable in the unused Room 1?

Generally a good idea, for several reasons. RFI is one such reason...
unterminated ports can "leak" RF, and some of the cable-TV channels
overlap with amateur bands (e.g. 2 meter) and aircraft/public-safety
bands. Cable companies are required to [try to] keep their cable
plants leak-free, due to the interference that these cable channels
can cause.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Thanks to everyone for all the good input.

Please tell me if the following would be the best solution. As mentioned
in my first post, my Room 1 which currently has the CATV outlet unused,
is adjacent to my main media room. Would it be best to run a coax from
Room 1's unused outlet through the wall to my main media room and have
no additional loss for one of my recording devices? Hugging the wall,
that would be a 50 foot run. I'm not sure how much loss 50 feet of cable
would create. Is RG-6 the best coax to run?

Also, I want to make the best choice for the existing 2-way split in the
main media room. What's the difference between...

- 1GHz 90dB 2-Way F-Pin Splitter
- 1GHz 130dB 2-Way F-Pin Splitter
- 2GHz 90dB 2-Way F-Pin Splitter DC Passing

I saw these at
http://www.national-tech.com/catalog...lsplitters.htm

Thanks to you all, I'm learning.

Jerry


Jerry wrote:

A question from a lay person. I'm looking for information on what kind
of CATV splitter to buy. I have Time-Warner analog CATV and don't use
any cable box. All my devices use coaxial RF cable as input. Here's my
setup...

Cable comes into my house's outside junction box into a 4-way splitter
with each output saying 7dB (whatever that means), then goes to four
rooms.

Room 1: Bedroom without any TV. Coax not terminated.

Room 2: Office with cable modem and TV. Cable company used a 2-way
splitter with each output saying 3.5dB.

Room 3: Bedroom with a TV.

Room 4: My main media room. Here's where I need the right coax splitter.
I currently have a 2-way splitter connected to a VCR and a TiVo. I'd
like to add a DVD recorder with a cable-ready tuner. All 3 devices would
have coaxial RF cable input.

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4. I saw such a splitter at Radio Shack. Is there a
better brand?

2. Should I terminate the cable in the unused Room 1?

Thanks for any suggestions.

Jerry

On Thu, 04 Nov 2004 00:14:26 GMT, Jerry wrote:

Would it be best to run a coax from
Room 1's unused outlet through the wall to my main media room and have
no additional loss for one of my recording devices?

Hi Jerry,

Don't make things difficult, just spend the big bucks for the high
price spread.

Also, I want to make the best choice for the existing 2-way split in the
main media room. What's the difference between...

- 1GHz 90dB 2-Way F-Pin Splitter
- 1GHz 130dB 2-Way F-Pin Splitter
- 2GHz 90dB 2-Way F-Pin Splitter DC Passing

DC passing would suggest that all these are rated for satellite TV
systems (hence the high frequency rating). The dB ratings are port
isolation (one side interfering with the other). Choose one with
highest number (either frequency or dB or both) in anticipation of
future needs - price is hardly an issue with these components.

73's
Richard Clark, KB7QHC

Port to port isolation is typically in the upper teens to mid twenties,
depending on manufacturer and frequency. The 90 and 130dB you see in
those specs (that appears to be about the only spec they give, in
addition to bandwidth) is the RFI immunity. One of the specs they don't
list is the return loss. Are the 90dB ones solder backed or epoxy? Are
they made utilizing a PCB design, or are the components just soldered
together and stuck in the housing?

Like Richard wrote, fork out the extra couple of bucks and get some real
splitters. One good place to get some is
http://www.cencom94.com/gpage.html. They're made by CATV industry
manufacturers and used by cable companies. Holland is Comcast approved
and PDI is widely used by Time Warner.


CIAO!

Richard Clark wrote:
- 1GHz 90dB 2-Way F-Pin Splitter
- 1GHz 130dB 2-Way F-Pin Splitter
- 2GHz 90dB 2-Way F-Pin Splitter DC Passing


DC passing would suggest that all these are rated for satellite TV
systems (hence the high frequency rating). The dB ratings are port
isolation (one side interfering with the other). Choose one with
highest number (either frequency or dB or both) in anticipation of
future needs - price is hardly an issue with these components.

73's
Richard Clark, KB7QHC

Most cable systems are designed to provide 15-20dBmV at the tap, which
equates to about 10-15dBmV at the groundblock. For safety's sake, use
the lower number in your calculations.

As you've seen and others have written, a 4-way splitter loses ~7dB on
each leg. The actual loss varies with the frequency. The 7dB is at
50MHz. In the 550-1000MHz bandwidth, it goes up to 8dB. Since the
higher frequencies have more loss through both the cable and the
passives (splitters), calculate using the loss at the high end of the
spectrum, which is 5-750MHz.

10dBmV going into a 4-way splitter has (10-8=) 2dBmV at each port to go
out to each outlet. RG 6 loses ~5.8dB per 100' (@750MHz), so an outlet
that's 50' from the splitter loses ~2.9dB in the cable. You had only
2dBmV to begin with and the cable is attenuating it another 2.9dB, which
means that you're going to have a signal level of -0.9dBmV at the
outlet. Throw in another 4 for a 2-way splitter, and you're down to
-4.9dBmV. Time Warner may run their systems with 20dBmV at the tap,
which would, so go ahead and add 5 to the above numbers if you want.
But that still leaves you with only +0.1dBmV at a 2-way splitter.

A pretty good rule of thumb is that if there are more than 3 outlets,
use a 15dB gain amplifier.

Always terminate unused outlets and ports on a splitter. There's
ingress and reflections to worry about.


CIAO!

Rich Gosselin wrote:

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4. I saw such a splitter at Radio Shack. Is there a
better brand?

*********************
Yes & no...if the splitter is a 1 gig splitter, it'll work. Don't use the
900mhz splitters...they'll work...so so...but you'll get better signal
through the 1 gig splitter, and they are not expensive...I get them at Home
Despots...about $5...can't remember if they are Ideal or RCA branded...you
will probably not need any signal amps...unless your really working with a
bad cable company. They take special care to boost their signal throughout
their network, and really try hard (in my area with Comcast) to pump good
signal to their users.
*********************

2. Should I terminate the cable in the unused Room 1?

*********************
Always terminate unused coax ends tied to the distribution network.
*********************


Rich