Do you always need a large OTA TV antenna? The answer is no. If you live in a large city or the suburbs of a large city, you can probably get by with rabbit ears or a slightly larger set top antenna.
The reason you don't want too large of an antenna is due to the digital signal you are tying to get being "too strong" which isn't good for your converter box or newer television with the built in tuner.
When I say you live within the suburbs of a large city I mean within 10 to 20 miles. Other factors can include the terrain of your area, how close and how tall immediate buildings are to you, and line of sight to the station transmitters.
Again, a good source for what kind of antenna will do is Antenna Web.
Here are a selection of small set top boxes good for city and close by suburb areas. The first one is made in the USA.