best standard dish and quad LNB for a SKY+ box and a SKY + HD box

as per title also the signal is at 50 %, at best when raining there is some channels dissapear could this be down to LNB and a standard SKY dish "I think at 47cm"

thanks in advance..

iam going to replace the dish and lnb on the sky setup any help on choosing what is best for this would be welcome, thank u all