#Transistor fm radio receiver circuit series

It’s still not the highest performance receiver in the world, but it’s astoundingly simple and in the early years of the 20th century it offered a huge improvement over the much simpler tuned radio frequency (TRF) receivers that were the order of the day.Īrmstrong’s regenerative receiver circuit. A small amount of positive feedback is applied to an amplifier that has a tuned circuit in its path, and the effect is to both increase its gain and narrow its bandwidth. How on earth could a single transistor form the heart of a radio receiver with enough sensitivity and selectivity to be useful, you ask? The answer lies in an extremely clever circuit: the regenerative detector. Two of the transistors formed the project’s audio amplifier, leaving the radio part to just one device.

#Transistor fm radio receiver circuit series

This book built the reader up through a series of steps to a fully-functional 3-transistor Medium Wave (AM) radio with a small loudspeaker.

It came courtesy of a children’s book, one of the Ladybird series that will be familiar to British people of a Certain Age: ’s Making A Transistor Radio. One of the first electronic projects I worked on was just such a circuit. It was not uncommon to see circuits with only a few transistors or tubes that exploited all the capabilities of the devices to deliver something well beyond that which you might expect. In those days people still used electronics to do a lot of the same jobs we do today, but they relied on extremely clever circuitry rather than the brute force of a do-anything super-component. There was a time when active components such as tubes or transistors were likely to be significantly expensive, and integrated circuits, if they even existed, were out of the reach of most constructors. Making A Transistor Radio, 2nd edition cover. Where once we might have used an op-amp or two, a 555 timer, or a logic gate, it’s ever more common to use a microcontroller or even an IC that though it presents an analog face to the world does all its internal work in the digital domain. It consumes only 1 mA.When we build an electronic project in 2016, the chances are that the active components will be integrated circuits containing an extremely large amount of functionality in a small space. The radio receiver cand be powered by a 9 volt battery. The external antenna must be coupled to the hot end of the coil through a 4.7 picofarad capacitor. The sensitivity of the radio receiver can be greatly improved by attaching an external antenna into it.

The coil must be installed as close as possible to the PCB. The tap is at the fifth turn of the coil counting from its ground end. The coil is 65 turns AM antenna wire around a 10 cm long x 10 mm diameter ferrite rod. The amplified signal is then delivered to a high impedance “earphone”. The signal is then filtered by C3 so that only the audio signal will be amplified by T2. The demodulated signal comes out from the collector of T1. The sensitivity of the receiver is dependent on the amount of feedback and can be adjusted by P1. The transistor T1 works as a feedback regulated HF-amplifier and function as demodulator at the same time. Although the circuit is very simple, it functions very well without external antenna or ground connection. It uses only 2 transistors and few passive components which makes is very easy to be constructed. This two transistor AM radio circuit is also called “mini-radio”.