Hi Anh Cuong:
Not sure about about Minnesota but in Toronto I mount the second LNB (for AMC 4) on the right side of the main LNB (when facing the dish head on). Its tricky to get a lock on the signal. You must aim the second LNB a little bit higher than the main LNB; and all dishes are a bit different. Most important thing is to have a dish big enough to catch both satellites; I use 39" dishes. With a smaller 33" its almost impossible. Also, connect the second LNB directly to the receiver -- don't wire it into the
DiSEqC switch until later -- and make sure you choose an active transponder on AMC 4 - like the one
VPTV is on. 12120 / VER / 30,000.
http://www.lyngsat.com/amc4.html
kat