>I saw once on Mythbusters where they were trying to make a large enough focused light to start an approaching ship on fire.

That's an ancient puzzle - supposedly it was Archimedes (or Euclid?) who set the approaching fleet on fire by concentrating the sunlight reflected of shields. The geometry would have to be quite precise, and the heavy tar the Greeks used back then should have helped absorb a lot of heat. It's been tried several times since, but I don't remember ever hearing anything conclusive.

>From what I remember, somebody went the satellite dish approach, but I don't remember the results. It was fun to watch though.

The focus should be in the end of the waveduct (or whatever's the name of the rod). It's already manufactured as a good enough paraboloid - for any practical use, we can consider both the sunshine and the satellite signal to come as parallel rays (although they are not exactly parallel), so what works for one, should work for the other. I expect the plastic cap on the end of the waveduct should melt in a few seconds.