Albert
You might want to check your azim/elevation and LNBF skew first before you change the LNBF. Go here to check all of that
http://sadoun.com/Sat/Installation/S...Calculator.htm
After you align your dish to the correct directions, if you still getting a weak signal, you could consider changing your LNBF (though no guarantees on getting the signal). Make sure your receiver can use a universal LNBF. Some receivers don't accept a universal LNBF only standard.
On a perfectly aligned dish I 've seen signal improvement of 5-8% when using a 0.5 db LNBF compared to a 0.6 db lnb.
Jamal