Matchbox Radio – No Battery

A coil discovery that may be of use to fellow amateur radio builders.
The use of a 1000uH axial inductor enabled the building of a good performance tiny radio, fitting inside a small matchbox.
Solar cell powered and able to run from the light of a CFL desk lamp when indoors, the radio does suffer from some mains noise if next to the power cord (as in the video due to having only 1 hand free) but otherwise offers great reception of AM stations.

It is based around the TA7642 AM chip, which resembles a transistor.
The application datasheet shows a couple of transistors and other parts on the output section, so those had to be worked around. The output from Pin 3 now goes through a decoupling cap (1uf) and out to a crystal radio type telephone speaker.
Audio volume is perfectly adequate for general listening.

Components used:
TA7642 AM chip
100K resistor
1K resistor
6pf capacitor
0.01uF ‘103’ capacitor
0.1uF ‘104’ capacitor
1uF capacitor
100uF capacitor
140pF variable capacitor
Piezo speaker
1.5V ‘calculator’ solar cell

TA7642 datasheet:

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