Economical Transistor Radio

The schematic diagram
shows an audio stage with a common-collector circuit. This does not damp
the tuned circuit, but instead actually increases its response. This
yields good sensitivity and selectivity. Due to the low supply voltage,
the subsequent audio amplifier needs three transistor stages. The volume
is adjusted using the potentiometer. This radio works well using an
internal ferrite rod (around 1 cm diameter and 10 cm long) with a
winding of around 50 turns of enameled copper wire. With a two-meter
external wire aerial, you can receive even more stations. This radio is
not only economical in terms of components, it also needs very little
‘juice’: since the current consumption is only 10mA, an alkaline AA cell
will easily last for around 200 hours of operation.

The specifications, very briefly stated, are:

  • medium-wave receiver with ferrite aerial
  • optional supplementary aerial
  • power supply 1.5 V/10 mA
  • 4 transistors
    l* oudspeaker output

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