None of the PCI nor USB FTA receivers have blind scan.
That's probably the most useful feature in a tune-up receiver.
Although somewhat complicated and expensive, USdownlink's idea probably works the best.
Well, if that's what you want.

Just don't drop your laptop off the roof.
You could possibly also connect a modulator to an antenna, and broadcast to just a portable TV set.
That's not technically legal, and I couldn't guarantee success, but it's another avenue.
Carrying a big TV set and STB out back is obviously a pain.
So, I took a page out of Linuxman's procedure, and use an LCD DVD player.
It has an external video (and audio) input, so acts as a monitor to a Mercury II.
Mine is about 7" size, and that's probably a bare minimum.