Poor picture quality

Paul007

I was wondering if anyone can help me with this?
Just recently the picture quality that transmits from my Global 4-way amp to my other Tv's is a bit snowy. It's still watchable but it's not crystal clear as it used to be.

The light still works on the Tv-link and I can change the channels ok.
The only way I've been able to get the picture perfect is by removing the analogue cable from the digibox or by bypassing the amp altogether.

I've looked for loose connections and tried changing the rf channel no. in the digibox menu but it hasn't had any effect.

Any ideas?

PK - the king

Try connecting the tv's using a different rf lead. If you are watching through cable, check the RF cable, as a bad RF cable will cause interference throughout the whole band. If you are watching bypass channels through an aerial, check the aerial is correctly alligned, as once again, a badly lined up aerial can feed a lot of interference onto what would other wise be free channels space. Alternatively, try setting the digibox RF output as high as possible (try 69) as usually, these bands are not used for cable TV or aerial transmissions.

Hope this helps.

Paul007

Thanks for the reply PK.

I tried changing the cables and setting RF Ch to 69 but no luck I'm afraid. If anything, the picture got worse.

It's been set to ch 60 for quite some time and I haven't really had any problems apart from when I initially installed the amp.

Also, I'm not using an aerial, the anolgue input is NTL.

Tony

It could be the input level is too high into the digibox, does the picture improve when you remove the aerial input into the digibox? If so you need to insert an attenuator to lower the input level.

tony

watty

Hold the NTL cable almost touching, but not connecting the input. See if picture improves.

The amplifier / combiner in the the Digibox Modulator *DOES* overload easily.

I'd also put ferrite "lumps" on the NTL cable to stop common mode interference, an Attenuator (try 6db and 12db, if you need 18, put them in series) and even a bandpass filter (try common and VHF part i/o of a VHF/UHF diplexor/ "Y" splitter/combiner) .

Paul007

Definitely seems as if the input is too high.

If I remove the NTL cable, the Sky channels are perfect.
If I place it slightly touching the socket the picture remains good but the terrestrial channels are obviously poor.

Why would the input be too strong now when it has been fine for so long?

Anyway, I'll have to pick up an attentuator and some ferrite clips in the next few days.
Hopefully that will solve the problem.

Thanks for the help lads.

Tony

NTL levels change as often as the weather. Try getting a variable attenuator and adjust for best picture, I'm not sure why you would need ferrite clips?

Tony

Originally posted by Paul007
Definitely seems as if the input is too high.

If I remove the NTL cable, the Sky channels are perfect.
If I place it slightly touching the socket the picture remains good but the terrestrial channels are obviously poor.

Why would the input be too strong now when it has been fine for so long?

Anyway, I'll have to pick up an attentuator and some ferrite clips in the next few days.
Hopefully that will solve the problem.

Thanks for the help lads.

Paul007

Re. Ferrite Lumps

To be honest Tony I was just going along with what LurkingIcon said - he seems to know he stuff.

Just one thing has me puzzled.
If the NTL input is too high for the digibox modulator, why is the Sky picture ok when I bypass the amplifier?

Tony

Pay no attention to him Paul, Watty is the expert around here:D

to answer your question the amp is probably suffering from overload, too high a signal level is as bad as too weak

Originally posted by Paul007
Re. Ferrite Lumps

To be honest Tony I was just going along with what LurkingIcon said - he seems to know he stuff.

Just one thing has me puzzled.
If the NTL input is too high for the digibox modulator, why is the Sky picture ok when I bypass the amplifier?