So I built this reflect antenna which works perfectly. The idea was copied from here http://uhfhdtvantenna.blogspot.com/, and the original design was an outdoor antenna model CM4221. Basically, you can build it with anything you have on hand. The cost is around 10-20 dollars if you don't have any spare materals left in your garage. The bolg above has a instrution how to build it.
This antenna is very directional, means you have to face it to exactly where the strongest signal comes. Since the DVB-T signal is tricky, it has a delay of several seconds then show you good or bad, it is better to use the analogue signal to guide you to the right direction. Tips, when you try to aim the signal, use Maori TV as reference. I found that's extremely useful. (In my area, Avondale Auckland, both Maori signal and DVB-T signal come from Waitarua mast, it might be different in yours).
The result is exceptional, I have a signal strength between 95-100 all the time, and doesn't need a amplifier to boost. Now it's good time to enjoy Olympic.
This could be a very good solution for those who cannot have an outdoor antenna and don't care about having this little weird thing beside their TV cabinet.
Have fun geeks.