30yards will be fine with decent quality cable. decent WF125 is the best bet for long runs.
http://www.aerialsupe...erial-cable-254-p.asp
Although the connectors are harder to fit because the cable is slightly thicker and it's not recommended for direct connection to the back of the box.
WF100 is slightly easier to work with but has higher losses over long runs
http://www.aerialsupe...erial-cable-385-p.asp
If the signal level is still low then IMO you are better off fitting a slightly larger dish than an amplifier.
(though to be honest, 30yards isn't that far)