This is really simple, It's not for those who have a very weak signal, but for those who already have a TV with an internal tuner and just want to use all the available features. Also, why buy an expensive antenna or spend more time building a bigger more complex one if this little thing may be just right for you?
If you know for sure you will need a really good antenna, I would suggest this other tutorial.
You don't need more than:
a balun impedance adaptor (close look below);
1m long rigid copper wire;
a stantard shoebox (if there is a standard);
some aluminum foil
a plier and some utility knives.
Oh, after the antenna is ready, you will connect it to the tuner through a RG-6 coaxial cable with F connectors, so you just might buy some of that at the hardware store too.
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Step 1: Active Elements
I call this antenna a folded dipole / bowtie because it looks like a bowtie, but it works more like a folded dipole.
You pluck 4 holes on the sides of the shoebox (the shortest sides, near the bottom). They should make a rectangle that is nearly 12cm X 30cm. Then you use them to shape a bow-tie with the wire and keep the ends near the centre.
Then you expose the conductor, cutting off a small section of the plastic coating (which you may keep to cover them once the balun is inserted).
Inserting the balun may be tricky, but it was pretty easy once I figured out I could use the plier to fold the conector's tips, use a small spike to widen the plastic coating and stick the balun's conectors right in it. You can always solder them later if you you're up for it.
Step 2: Profit!
Now I want to say I only included the reflector because the shoebox's height is just the right distance (1/4 wave-length), so you don't really have to go through that step. An effective reflector should be considerably larger than the dipole, but it's just so easy to wrap the lid in aluminum foil, that I just couldn't resist it.
You can use a hole at the side of the box to insert a coax cable (make sure it's RG6 for UHF signal).
Step 3: Disclaimer
If you want a true bow-tie, you have to go through one extra step. Cut the wire in half and connect the ends so you will have a triangle (the closest thing to a cone for a wideband antenna).
I did that on another crude version of this setup I had done before just for comparison. It didn't make much of a difference performance-wise. The pictures show what the bow-tie antenna should look like.