I want to mount my TV tuner inside my laptop and I also want to build an internal antenna. In my area, TV stations are in the frequency range from 500MHz to 750MHz (as determined from my channels.conf file) which according to this online calculator puts my ideal antenna length (for a dipole antenna) at between 90 and 150 mm per half.
I wanted to get a better feel for the best antenna length to use, so I rigged an antenna like this:
and I scanned for channels several times, each time cutting 4 mm off of the end of each lead. I recorded the number of channels detected with each setup and then made a plot of the results:
While 128 mm was the best length, there is quite a bit of noise in the plot, so its hard to say for certain that the best length might not be somewhat shorter or longer. There definitely is a tendency for the longer antennas to do better than the shorter ones. Based off of this, I'll probably end up going for a 130 mm antenna, if I can make it fit in the case.
Also interesting: The 128 mm antenna picked up 34 stations, while the high quality antenna that came with the tuner picked up 37 channels. Overall, I think that is pretty good for an antenna made out of a couple spare pieces of wire.