This project started as an experiment to see if a fairly small area coil could be used as the basis of a crystal set that would work without an aerial. The components used had to be readily available, cheap and require little or no soldering, so that it was suitable for people new to radio and electronics.
It was decided to make the coil on a piece of cardboard 34cm × 24cm, which can readily be obtained from a large box of Cornflakes; the circuit was to be built on a Terminal Strip Connector. Unfortunately, many modern components have very short leads and this meant that they had to be extended by soldering on short lengths of tinned copper wire.
To keep the costs down, a variable capacitor has not been used for tuning. Obviously, replacing the fixed tuning capacitors with a variable device extends the scope and range of the project, as does using different coils of wire and adding an aerial.

After some experimenting, a successful crystal set radio receiver was made for the Medium wave band which readily picked up three stations - Absolute radio, Talk Sport and Radio 5 live. It was also found that the radio could be adapted to pick up Radio 4 on the Long Wave, though weakly. All of these stations are transmitted from Droitwich, Worcestershire, which was about 20 miles away and which is home to some of the most powerful broadcast transmitters in the UK.
Medium Wave Cornflake radio
Attempts to incorporate a Long Wave coil into the crystal set receiver were unsuccessful as the extra wire needed for the long wave coil significantly affected the Medium wave coil. In the end a separate design was made for a crystal set radio for the Long Wave band (Radio 4).
Long Wave Cornflake radio
Long Wave Cornflake radio picture
The next part of the project was to design a small amplifier that would power standard earphones instead of the sensitive crystal earpiece needed for the crystal set radios. The circuit was to be powered by a 1.5V cell. In testing, it was found that the amplifier would also power a small 64Ω loudspeaker.
Cornflake radio amplifier
For people not living so near to high powered transmitters, a version of the Cornflake Radio was also built using the TA7642 IC. This IC provides significant amplification to the received radio signals.
Cornflake radio TA7642
The final part of the project was a low powered transmitter to work with the Medium wave radio.
Cornflake radio transmitter

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