Going back to the times when radios had antennas attached to them for transmission as well as reception of signals, it's probably not a common sight to see such gadgets in use. Mainstream technology offers us real-time options to communicate with one another on computers via the internet as well as enjoy listening to news and music streamed into media players. However, nothing beats the rasp and crackle on the conventional radio as a means to connect into the unknown.
A radio antenna's main function is to convert radio frequency signals picked up from the air by its receivers, into electrical signals to produce audible sound. If the radio is also meant for transmission, it then converts electrical signals, which represent a human's voice or a song, into radio frequency signals and emit them. Since these signals travel through the air, there is always a great chance of signal loss depending on its surroundings. Any electrical device radiating some form of frequency can affect the radio's transmission and reception. An antenna constructed of incorrect height and material is also subject to further interference.
Radio stations sport giant antennas to ensure strong signal transmission to its listeners. Hence, radio antennas attached to the device itself are quite sufficient to pick up these strong signals without having the need for secondary antennas. The trick, however, is to adjust the antenna to pick up the best reception possible. Since radio signals travel as waves, the antenna height plays an important role. Simply extending it to its fullest doesn't automatically ensure good reception.
If you are staying in the outback away from civilization, an outdoor antenna may be required to pick up and transmit stronger signals. Ensure you place it in a clear area on high ground for maximum effect. Within city limits, an indoor antenna is a good alternative to avoid a sore thumb in your garden. Normally attached to the highest part of the house, insulated wire is run from the antenna to the radio. There is no hard and fast rule on which antenna heights work best. It all comes down to testing and tuning for what best suits your environment.