We live in an are where we can get a television signal without a satellite and when we bought our new hdtv television we had to get a special HDTV antenna coupler.
Also I recently learned that there are antenna couplers for cell phones. It helps to boost reception and output on your cell phone when you are in a weak signal area.
It can also increase data rates on 2G and 3G networks. You don’t see them often since they can be pretty expensive and rather cumbersome.