Where are you located? In Mexico City not even a 2.40m dish would do the trick.
Hello gonzalo, if the person at least receives some levels there's always a solution....
what gain (size) is needed is what he needs to research.
Regarding DBS satellite signal (not only 119 W):
I had problems with 1.8 m and I solved with 2.4 m
I had problems with 2.4 m and I solved with 3.8 m
I had problems with 3.8 m and I solved with 5.0 m etc, etc, etc.....
how much do you want to invest might be the limiting factor.
As I have posted previously:
1.- Key factor: he receives some transponders.
2.- Difficult variable: He wont post antenna brand (we also need to know size, gain).
If you don't use a well know antenna brand you can't calculate or proyect your needed gain.
Also there are cheap spectrum analyzer that can give dB and you could calculate or project the needed gain.
In fringe when things aren't achieved with 1.8 m nor 2.4 m things get tricky and expensive.