This is two transistor and two IF transformer based superheterodyne receiver which is designed to receive 13m to 41m bands. With quiet good external antenna this receiver performs similar to commercially available shortwave receiver and its audio quality is in very satisfactory level.

Prototype version of superheterodyne shortwave receiver.
Prototype version of superheterodyne shortwave receiver.

During our prototyping we test this receiver with several oscillators and rod coils. The best configuration which we found for 13m - 41m bands are described in below illustrations. Standard shortwave oscillator coil (Green) and rod coil are also working with this receiver but it will narrow the bandwidth of the receiver. For rod coil use 100mm to 160mm ferrite rod. The antenna which we use with this receiver is 2 × 12 feet T antenna.

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Rod coil winding details for the shortwave receiver.

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Oscillator coil winding details for shortwave receiver.

This receiver can be constructing on PCB, breadboard or commonly available veroboard or stripboard. For tuning use Polyvaricon or air variable capacitor. For precision tuning, connect small trimmer capacitor with parallel to variable capacitor’s gangs or use mechanical wheel assembly with the variable capacitor.

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Yellow and black IF transformer pin-outs.

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Common oscillator coil pin-outs.

This receiver is design to work with 9V regulated power supply and it requires external AF amplifier to drive the headphone or speaker. In our testing we use TDA2050 audio power amplifier with this receiver.

With small wire antenna this receiver is capable to receive most of the stations which including CRI, BBC World service, All India Radio, etc. in Sri Lanka. To receive other stations which including VoA, Radio France, Deutsche Welle, ABC we use our 2 × 12 feet T antenna.

For initial IF transformer tuning we recommended to use quiet large antenna and some powerful station. For example in Sri Lanka, CRI (17855.00kHz, 17730.00kHz, etc.) or AIR (11710.00kHz, 13710.00kHz, 9690.00kHz, 11620.00kHz, etc.) are quiet easy to locate and tune.

Project Related Downloads


Schematic and inductor details of superheterodyne shortwave receiver project.

References


KSP10 - VHF/UHF transistor
OA91 - Gold Bonded Germanium Diode