The stock is up over 1,000% in the last six months.Shares of AST SpaceMobile (ASTS -3.75%) were up as much as 20% this week before falling, according to data from S&P Global Market Intelligence. The satellite broadband company has been on a tear this year, up over 1,000% in the last six months alone. Investors are optimistic about the start-up's potential to disrupt the cellular broadband market and its huge addressable revenue opportunity.Here's why the pre-revenue start-up AST SpaceMobile was volatile yet ...