pixelling except on bbc and itv channels

[colinheath]

hi all,
i have problems with my system at the moment and would really appreciate some help
i have a standard sky digital dish with the amstrad dx100 reciever.
its been playing up for a little while and i think the dish may have moved a bit but have tried moving it back with no success. i live 12miles south of bath in the uk. i have had good reception for 3+ years now but its getting worse. now the funny thing is i can get bbc1 bbc2 bbc3 itv1 2&3 without any probs but the sky channels pixelate terrible and start and stop. it gets better with moving the dish but i cant get rid of it. im a fairly competent electronics amateur so should be able to sort anything simple myself.
now do the channles i list come from a diferent satellite than the others or something? could i be justa fraction out of alignment. i must say i moved this disha year or so ago and it was fine setup on the servies signal meter. iv got nearly full strength and 2 thirds on quality(higher than when sky engineer installed ;)
EDIT. ok so i did some reading and that means im only getting good signal on 2D satellite then right?
so are the other satellites lower in the sky than 2d from britain? reason i ask is im just clearing the roof line here and may need to move my dish up the wall a bit i think?
thankfull for any help
colin

 

[PoloMint]

Hi Colin

It could the tuner in your box is dying, of the LNB is faulty.

If possible try your box on another dish, if it works there then it’s likely to be the LNB, if not it’s probably the box.

If you get a good signal from 2D on your dish in the UK then you should receive all the other Astra2 satellites, they are all in the same orbital position and have a strong UK coverage.

 

[Bitman]

The other common factor is that the BBC and ITV transmissions (and everything else on 2D) are also on lower frequencies than the other channels.

Check out Performance Channel - that's in the lower half of the band but not on 2D.
If you get good reception on that as well, then it would indicate a frequency-sensitive problem.
That's likely to be caused by the LNB, not the dish alignment.