Request: Splitting Ntl anologue signal

cubix

Like alot of people here the mate was not getting a great reception on some of his ntl cable channels(discovery/E4/Tv3 etc). So we ran new ct-100 cable from the ntl pod that runs on the out side of his house into the attic and put one of those metal F type splitters(4 port) on and ran more ct-100 cable into each room. Now I am being very picky as the reception is 100% better but on some stations the reception has a very very slight herrinbone. Nearly sure the splitter is causing some interference because when you unplug all the cables and get a F straight through connector and plug in each room to the main feed the signal is 110%.

Picked up a F connector booster from maplins but it actually made the signal on most stations worst so I can only presume its making the signal to strong. So I am wondering has anyone got any words of wisdom on different makes of splitters. The one we are using was got in power city and is more or less identical to this one from maplins http://www.maplin.co.uk/Module.aspx?ModuleNo=29531&criteria=tv%20splitter&doy=15m4 except PC's one was €6 and maplins is about €16. I know alot of people say you get what you pay for(myself incuded) but I used the same splitter on the mums setup and could not fault it.
Does digital cable tv suffer like anologue tv as I once heard someone say either it(digital) works or it doesn't. Where as with anologue it seems you can be lucky when splitting the signal. Whats the most ports on a ntl pod outside their house has anyone seen?. The one on the mates seems to be the standard 4 port, 2 for him and 2 for his neighbour. I presume that ct-100/125 is the best cable with in reason for signal lose also is it over kill to use it internally instead of RG6. Another words when you have run ct-100 up from the main box into the splitter in the attic.

Thks for reading

watty

The amplifier is designed for a TV aerial with not too many signals. A cable TV signal has many signals so a less than perfect amplifier will cause the channels to interfere with each other.

The splitter reduces the signal by 1/4th to 1/8th depending on how well made, the cable/sets then have a weaker signal more easily interfered with by a outside signal such as TV or DAB from Three Rock.

It isn't overkill to use CT100 as the better shielding and lower loss helps.

You could try 12dB attenuator in front of booster if its gain is 18dB or 21dB.

As digital signal gets weaker / noisier the degradation is not as obvious as Analogue. At first there is no effect, then the picture looks a bit over compressed and then blocky, finally intermittant still frames before you lose it.

The splitter is probabily OK, it is just that even if it was perfect there is only 1/4 the signal. You need a 12dB amp just in front of it which needs to be be for cable TV not an aerial to cope with the number of channels simultanously.

Many "Boosters" are 18dB to 22dB and will "intermodulate" with a large number of channels (herring bone).

You could try one of these:
http://www.maplin.co.uk/Module.aspx?TabID=1&ModuleNo=29413&doy=15m4

Can't say it will work, use the VHF/DAB input and maybe 6dB or 12dB attenuator between it and the NTL cable in.

cubix

Thanks for that watty,that was the booster I got expect the 8x one. On the digital side of things can anyone here who has chorus mmds digital tell me if you choose to have multiroom viewing do they run extra cables from the ariel or just split the one coming into the house. With ntl cable if you order extra rooms they seem to run an extra cable for each room from the pod outside under your eves.
The setup in my place (chorus anologue) is it comes in from the road(underground) to the side of the house with what looks like ct-100 or similar. Then in the utility box they split it with a standard passive splitter into two RG59 cables which where pre installed. Some people in my estate have gone for the chorus digital mmds ariel as they are not supplying digital via the cable yet. The installers seem to have run one cable from the ariel on the roof down to the utility box on the side house and stuck it in the splitter where the anologue cable was. So I am just wondering how well does a mmds digital signal travel on RG69(cables pre installed in the house) and also how does the signal cope being split.Can anyone tell me for sure if you go for multiroom viewing that there should be a splitter device on the ariel and x amount of cables run down for each room that you need

Cheers

watty

The Chorus Digital MMDS signal is converted on the roof to a signal very like Chorus Digital Cable TV.

The cabling is not a big issue. The biggest issue is a good enough signal on the dish so the picture doesn't freeze or pixellate.

cubix

Thanks for that big fella;)

Antenna

watty wrote:

Can't say it will work, use the VHF/DAB input and maybe 6dB or 12dB attenuator between it and the NTL cable in.

Many cable areas have cable signals at the low end of UHF as well as VHF - that complicates matters considering this has seperate VHF and UHF inputs. Also it may give poor signal, if anything at all, on cable channels using Band 1 and hyperband (no specs given as to frequency range) -
The VHF input is probably only for Band 2 (FM radio) and Band 3, which leaves out several cable TV channels below Band 2 and above Band 3.
It looks to me as if it is intended for aerial - not cable - use

watty

It is very hard (as I suggested) to buy retail an amplifier that will cope with cable TV signals. The filtering on the amplifiers is pretty rubbish, the problem is overload with sheer number of channels.

cubix

Forgot to ask Watty but if they only run one cable from the mmds ariel on the roof to the side of the house and split it instead of running a seperate feed from the ariel to each room you require are you sure this does not weaken the signal?. The reason I ask is because this is the problem the mate is having on his ntl (cable) when he spits the signal for two rooms instead of paying ntl an extra €5 a month so they will run a cable for the second tv straight from the pod outside or is the signal that comes down the cable from an mmds ariel stronger than a cable signal.

One last question I have is, out are way you can get either ntl digital or chorus digital via the mmds ariel system. Do either chorus or ntl give you the anologue stations on the mmds ariel system? ie:you could watch the anologue stations in a room that does not have the set top box

Cheers

watty

The analog on MMDS is terrible. Most of the analog channels on Chorus MMDS need the Jerrold descrambler which does no favours to the signal quality either. Chorus are likely to ditch it soon so as to have full cable digital lineup. Chorus/NTL now UPC. I think NTL already have.

Yes the split does weaken the signal, but the convertor from 2.5GHz to cable TV frequencies boosts it enough that it can be split once.

rogue-entity

OP, you said you ran a new cable from the NTL "pod" that is outside your house and are now running it (via a splitter) straight into your TV's (in the different rooms). If these TVs dont each have an NTL point, or you dont connect the cable going into the attic into one of these NTL points before splitting it to the different rooms. You are breaking the law, and certainly your NTL T&Cs. NTL require you to pay additional rent for each point that they install but the wire after the point is yours to do with what you want, including splitting it to differnent rooms. The other reason you should pass it through an NTL point is to screen out the radio stations that are also transmitted on the cable and to add lightning protection.

Talisman

Apologies for jumping in to somebody elses thread - I have a related question.

I've recently put together a htpc which resides under the television and I want to split the NTL signal between it and the tv. I've tried using a 2 way aerial booster but the quality of the picture deteriorated significantly, presumably because the signal was already strong enough and the boost just amplified noised. I'm now looking to use a 2 way F splitter, and have been told to keep the cable length as short as possible. I've had a look at the Maplin site and they have the cable and splitter I think I need.

2 Way F Splitter
F Plug to Plug 1.5m
F Plg to Coax Plug 2m

Will the cable length make a significant difference? The current cable is about 1m in length and is more than long enough. If this equipment is correct then using the cables from Maplin would make one tv connection 3.5m from the NTL box and the other approximately 3m from the box.

watty

A few meters of cable is insignificant at these frequencies.

Talisman

I decided to make my own cables and hooked them up tonight.

Components used:
2 Way F Splitter
Satellite TV Cable FT100
Twist-On F Plugs
Coax Plug to F Socket Adaptor

I made 3 cables, each approx. 50cm in length and tested them by connecting them directly from the ntl outlet to the tv and capture card. Everything was great, then I connected the cables to the F-Splitter and the signal became a mess. The splitter it would seem is introducing quite a bit of interference.

What options do I have now?

Talisman

Problem solved - it was the F Splitter. I reversed the connections so that the NTL box was connected to an output and then connected the tv to the input and the reception was perfect. Connecting the cable from the NTL box to the second output caused the interference to reoccur. I've swapped the splitter with another and the interference is gone. :cool: