The problem with a radio constructed like this is that it requires a radio frequency (RF) amplifier that is both very strong and very selective. It has to amplify only one selected carrier wave (or one selected radio station) and nothing more. This is very difficult to accomplish since the RF amplifier has to amplify the received signals many, many times. Therefore, the RF amplifier has to have a large number of stages, each of them complete with radio dialing circuitry.