how badly to cable splitters affect tv quality?

[nageov3t]

so I got my new cablevision hd-dvr this week and, well... let me just say that it sucks. lol. the interface is slow and clunky and just a pain all around to have to attempt to navigate through (there's not even a way to search for shows by title, as far as I can tell).

all in all, it has me thinking about hooking my htpc back up, but I don't particularly feel like having to invest in hd tuners, ir blasters, etc, so I think I'm going to try just using the cablevision hd-dvr to record the shows I watch that are broadcast in HD (mostly anything off of network tv... nbc, abc, fox, etc) and using my htpc to record the shows that I watch on cable, at least till I get the inclination to invest in HD tuners and the like.

but how much would setting up a splitter (1 connection to the set top box, 2 connections to the htpc) kill the picture quality on the hd dvr?

 

[TastesLikeChicken]

Noody can really tell you what you're asking because it all depends on the specific signal quality you are getting through your cable line. HD is digital as well so there is no real degradation in picture quality. Either the split signal will be strong enough, in which case you'll get an HD picture, or it's not strong enough so there won't be any picture at all. There's really no in-between, though it's possible that if the signal was right on the edge of viability you could get some macro-blocking.

Personally I can't split the cable line in my living room and route it to both my HTPC and HD-DVR. The signal is not strong enough. Instead I rerouted another line into the living room so each gets its own feed from the primary splitter where the cable enters the house.

 

[s44]

Two words: HD Tivo.

 

[nageov3t]

Originally posted by: s44
Two words: HD Tivo.

would be ideal, but I'm not quite willing to put down the huge chunk of change for the unit + more monthly fees on top of what I'm already paying for cable.

 

[Cardio]

Just get a good quality drop amp splitter that will maintain the necessary signal strength to both units. This is not a RadioS item. Just search on eb for CATV Drop AMP and get one with the right number of outputs for your needs. Should cost around $20. This is what cable companies use. Use good quality RG6 cable and you will have as good as original signal. The signal you receive from cable has been split and amped numerous times before it reaches you. Do not use the simple splitter amp that has been around forever for about $10 as it does not have the needed bandwidth. Sames goes for a splitter, it must pass at least 1GHZ. If you call your cable company and explain what you intend to do and say you do not have enough signal strength after splitting they will likely install and amp for you at no charge.

 

[Tifababy]

I had issues with my signal strength when I first got my HD-DVR from the cable company a few years ago. The technician told me that a typical household would have a signal around 10dB when it enters the house and for an HD signal you don't want the signal to be much below 0dB. This is the equivalent of about two 4-way splitters. For analog tv, you can go as low as -30dB and still have a strong enough signal to watch tv.

 

[The Boston Dangler]

loki, what kind of cable box do you have? if you provide me with the correct answer, i can conjure your signal levels from the ether. usually there is a program title search, but it is clunky as Hell.

a good 2-way splitter passes up to 1GHz, with 3.5 dB loss on each leg. an unbalanced 3-way splitter will have losses of 7, 7 and 3.5 dB. honestly, just go to the cable co. and ask for one. the window of operation for QAM modulated video is -10 dBmV to +10 dBmV. adding an amplifier without measuring levels is not a good idea, they typically have +15 dB gain. also the added distortion doesn't help. most people with cable amps definately don't need them. analog performance will vary with the tuner, but less than -10 or -12 dBmV and you'll be reaching for rabbit ears and tin foil.

 

[s44]

Originally posted by: loki8481

Originally posted by: s44
Two words: HD Tivo.

would be ideal, but I'm not quite willing to put down the huge chunk of change for the unit + more monthly fees on top of what I'm already paying for cable.

Well, the new units are $300 or less, and the cablecard fee may be less than the box fee, making the net monthly cost not that bad either.

But I was mostly thinking of the cost of a HTPC setup, since two cablecard tuners alone (assuming they work -- and can you even buy them unbundled yet?) puts you over the price of the Tivo.

 

[krotchy]

When it comes to digital HD you are pretty much going to get all or nothing I find, but only on specific channels. Once the levels are too low on one channel, you will see giant blurry blocks all over the place, its impossible to miss.

For instance, comcast hooked up cable in my new place, and the builder put a -7db 4 channel splitter in the low voltage channel, then by default in my living room put a -3,7,7db 3-way splitter in the living room and put internet on the 3db line. Now my perfectly fine quality HD cable was being dropped 14dB from the wall before it got to my cable box, and I was unable to get certain Hd channels (as it turns out, anything above the internet broadcasting frequencies in the spectrum, due to the higher frequency rolloff)

A second comcast guy came out and fixed it by putting a 3,7,7 spliiter in the low voltage closet, then moving the HD box to the 3dB giving me +7dB for my cable and keeping internet and my TV's dB levels the same.

Long story short, you really cant be sure until you try it. it is also worth playing with the configurations, since different wiring setups and whatnot can rolloff higher frequencies faster than others, and new HD channels and Internet tend to be on the higher frequency channels. You might try getting a 3,7,7dB splitter and putting the 3dB on the cable box and the 7dB ones to the computer, since they are decoding the lower frequency stuff and should be fine and not lose anything

 

[cheesehead]

I agree with Krotchy. Go check what sort of splitter you've got, and perhaps do a bit of re-arranging

 

[cubby1223]

Originally posted by: The Boston Dangler
loki, what kind of cable box do you have? if you provide me with the correct answer, i can conjure your signal levels from the ether. usually there is a program title search, but it is clunky as Hell.

a good 2-way splitter passes up to 1GHz, with 3.5 dB loss on each leg. an unbalanced 3-way splitter will have losses of 7, 7 and 3.5 dB. honestly, just go to the cable co. and ask for one. the window of operation for QAM modulated video is -10 dBmV to +10 dBmV. adding an amplifier without measuring levels is not a good idea, they typically have +15 dB gain. also the added distortion doesn't help. most people with cable amps definately don't need them. analog performance will vary with the tuner, but less than -10 or -12 dBmV and you'll be reaching for rabbit ears and tin foil.

Even 3 way splitters aren't always that good, I've found out. If it's a concern, there are taps which are asymmetrical splitters, with one output a 1db drop, the other a 6db drop, and that's what we had to use to split the signal between the digital cable box, and analog htpc dvr tuner.

 

[The Boston Dangler]

they're called directional couplers. a 2-way is actually a dc-4. there's dc8, 12, 16 you get the idea