Homemade SW Converter
Homemade converter schematicConverter schematic is similar to the industrial SW converters, for example SW Converter 1936.
But in the instance of the converter described were used widespread details. Variable capacitor from "Kazitskogo" factory has aluminum plates made by type capacitors, applied in 34 - EKL factory receivers. Structurally these capacitors is better than gilt - their plates are made of aluminum and are attached at the ends of combs. Consequently converters such capacitors are less prone to microphonics than converters with gilt brass plates, extremely elastic and therefore easily amenable to vibration. Unfortunately, the aluminum capacitors overlap is slightly worse than the gilt, but this shortcoming has to put up.
Inductor type high-frequency RF Dr 1. These reactors were commercially available everywhere. The filter consists of a resistor R3 and two capacitors C5 and C6. Capacitor C5 - 4 mkF, capacitance C6 - 2 mkF. Resistor R3 should be about 5000 Ohm. Resistance R1 approximately 1 Mohm, resistance R2 of about 8000 - 12000 Ohm.
Aerial capacitor C1 at a few pF capacitance has an interesting design. Piece of conductive wire for 20-25 mm wrapped with 3-4 layers of paper or adhesive tape. It is also possible to apply the cable isolation, etc. In general, the insulator layer should have a thickness of about 1 mm. On top of the insulator close, ie coil to a coil is wound in one layer of an enamel wire, with diameter of 0.8 - 2 mm, the length of the winding must be about 20 mm. Wire will serve as one plate of the antenna capacitor C1, and wound over the insulation layer of a thin wire - the other electrode.
The capacitor C3 must be equal to approximately 5000-10000 pF, capacitance C4 - 30 pF, capacitance C7 of 300 - 500 pF. Coils L1 and L2 are wound on a common frame with a diameter of 20 mm and a length of 20 mm, too. Coil L1 consists of 6 turns of wire 0.5-0.7 in enamel insulation, tightly wound coil to a coil. Feedback coil L2 is comprised of 8 turns of wire too 0.1-0.2 enamel insulation. This winding is divided into two sections by four turns each. These sections are arranged on either side of the tuning coil is about 2 mm from the coil. If, during the test of the converter to be clarified that the converter does not oscilate in the entire range, the feedback coil windings should be somewhat closer to the coil configuration.