Readers that have simple audio amplifiers without any accessory can easily use it as an MW tuner (medium wave), that is, as a powerful common radio. The design we describe uses few components and can be connected to almost any amplifier. (figure 1)
What we have is a straightforward, simple receiver stage that can tune in to medium-wave stations with a small antenna.
For difficult reception locations an external antenna may be used and if the amplifier is powered by batteries or battery, the ground connection must be made. With amplifiers powered by sources or mains, this earthing is dispensed.
The terminals strip is shown in figure 2.
The L1 coil can be commercially available in medium waves, harnessed from old radios or else rolled up by the assembler. It shall be formed of 80 turns of enameled wire 28 with a plug in the 30Â ° loop from the ground side, in a ferrite rod of approximately 1cm in diameter, 10 to 15cm in length.
The variable is common and the transistor is high gain BC549. All connections should be direct and short. The output cable to the amplifier must be shielded to avoid the presence of snoring.
The power comes from 2 or 4 small batteries, that is, with 3 or 6 V.
