TV signal splitting

[Grayham]

I asked this in the video forum and nobody answered..

How many times can you split a TV signal before it starts to go down the crapper? I see TV signal amps in hardware stores with the splitters.. do these correct the poor signal after many splits?

 

[ScottMac]

No, actually not. The time to amp the signal is before the splits. Every time you split the signal, the signal level and the noise floor level get closer. After so many splits (depends somewhat on what the signal level and the S/N levels were before the split), amplifying the signal just amplifies the noise right along with it .. no real performance gain is achieved.

It's like this: every time you do a two-way split, you half the signal, and lose a little of the signal from each split because of the losses in the (passive) splitting device. If you split again with a passive device, you're down to below 1/4th of the original signal level (~7-8 db down). This is about as far as you can split a common signal without seriously affecting the quality.

Unless you have a good Field Strength Meter, there's no way to really tell what level you're starting out with.

You CAN have too much signal. A signal that's too hot looks worse then a weak signal in many cases.

There are (as usual), many variables that modify the above statements but, generally speaking, that's it in a nutshell.

Good Luck

Scott

 

[SuperPickle]

Originally posted by: ScottMac
No, actually not. The time to amp the signal is before the splits. [/i]

Exactly. I rigged up my parents' place with cable hookups all over the place. The signal sucked eventually so I tried to place an amplifier (+10dBx5 outputs, I think) just before the "most important hookups." It didn't do much good at all. Then, I took that splitting amplifier to the original split (originating from the pure signal from the wall) and everything was dandy.

Amplifying a clean, unsplit signal=good (if you don't overkill)
Amplifying a split signal=polishing a turd

/edit: speeling
BTW: Welcome to the AT forums

 

[0roo0roo]

radioshack amp buy as many or the one you need. i think after 50ft or so you totally need an amp... tv is pretty weak

 

[VictorLazlo]

It depends how much signal you have coming into your house, typically 10dB (+/- 5dB)
A 2-way splitter doesn't cut your signal in half, it cuts each leg down 3.5dB.
A 3-way splitter cuts two legs down 3.5dB, and one leg down 7dB.
A 4-way splitter cuts all four legs down 7dB.
As long as your signal is in the neighborhood of 0dB or better when it reaches the cable box or tv, you are golden.

You may have problems using a radioshack/third party amp if you have digital cable. Digital cable boxes need two-way communication (video on demand) and some third party amps interfere with this. Time Warner (Brighthouse) techs carry three different approved amps with them:

1-port: +15dB
4-port: +7dB each leg
8-port: +4dB each leg

Also, never connect an amp in front of a cable modem. It will interfere with communication, and cable modems don't need much signal anyway. Amping it won't make your modem go faster. In fact, techs also carry special splitters to knock down the signal when it is good for tv, but too high for the cable modem.

Using an amp is rarely ever justified. 99% of problems are fixed by replacing bad cable runs, bad splitters, or the occasional bad tap.

 

[Mark R]

If you are getting a poor quality signal it is best to deal with it at source.

Check your aerial - if it is old and has bits missing, then it may be worth replacing it with a new high-gain one. You also need to check that it is oriented in the correct direction.

If you live in a weak signal area, or if your aerial is a long way from your TVs, then it is well worth installing a 'masthead' amplifier - this is an amplifier/splitter that sits on the pole just under the aerial - it is the best solution as it gets the cleanest signal possible and then boosts it up. Placing an amplifier later will get a weak, noisy and distorted signal and boost that up along with all the noise and distortion.

A large amount of signal loss occurs in the cabling - high frequencies don't go down cables well. Domestic TV co-ax really isn't good enough for long runs. Satellite dish co-ax is much better (better even than 'heavy-duty low-loss TV coax')

If you want to split the signal and need the signal to go a long way from the source, then it is essential that you split it as close to the source as possible - ideally with an amplifier. If you have to split later, then an amp may not do as much as you hoped.

 

[capybara]

and amps are rated db boost and noise factor. the radio shack amps arent the lowest
noise ones you can get, but they are cheap and available

 

[xer0x]

it all depends on the coax ,splitters, and incomming signal

i split my cable 17 ways
1 three way spliter
2 eight way

no they wernt amp'ed

wired all our rooms in the house, twice (one on each wall) made my own ends

8 tvs (dont ask)
1 cable modem

all tvs looked fine
and no loss of sync on my modem

 

[Bad Dude]

Originally posted by: xer0x
it all depends on the coax ,splitters, and incomming signal

i split my cable 17 ways
1 three way spliter
2 eight way

no they wernt amp'ed

wired all our rooms in the house, twice (one on each wall) made my own ends

8 tvs (dont ask)
1 cable modem

all tvs looked fine
and no loss of sync on my modem

So how did you do that? There has got to be some lost somewhere? Perhaps you have small TVs ? What kind of splitters did you used?
Thanks.

 

[xer0x]

i flagged down a cable guy and asked him if i can have spliters
he gave me three 8-way and two 3-way

using RG6 and digicon connectors

a 36 inch, 27, and the rest 19in



i haven't had ANY problems... so far