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