CB-to-SW down converter

This converter enables long distance (DX) reception of AM or SSB stations in the 27-MHz citizens’ band (CB) on a short-wave or medium-Wave radio (note, though, that AM or SSB modulation in the 27-MHz CB band is no longer allowed in a number of countries). The converter consists of a prestage, T1, and a mixer/oscillator,[…]

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S-meter for short-wave receivers

Some radio amateurs are very keen on accurate RST reports, others (mostly the VHF/UHF fraternity) never look at the S-meter on the receiver, and are satisfied as long as they can hear the other station. This circuit is the first group. Traditionally, one S-point corresponds to a 6-dB increase in signal strength, while ‘S9’ is[…]

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Simple d.c.-to-d.c. converter

To keep the converter simple, it contains no preset controls, which means that the level of the output voltage is dependent to some degree on the load. In theory, the output level is twice the level of the input voltage, but, owing to losses in the converter, that level cannot be attained. The main losses[…]

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D.c.-d.c. converter

D.c.-d.c. converter: The converter raises a direct volt-/ age to almost twice its level and is, therefore, particularly suited to increase the output of solar cells to the level required for charging lead-acid or NiCd batteries. It can deliver a current of up to 3 A. Measurements with a load current of 2 A is[…]

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Voltage converter 2

Voltage converter 2: Although a 9.5-24 V direct voltage can be brought down to 5 V easily by a standard regulator, 1 the converter described here has the advantage that, since it is a switch-mode type, it hardly dissipates any heat. Its maximum, steady output current at 5 V is 250 mA, although it can[…]

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Voltage converter 1

Voltage converter 1: The unit described is capable of converting a 70-260 V r.m.s. alternating voltage into a 180-350 V direct voltage. For that, a full-wave rectifier, contained in an MC34161, is used as a voltage doubler at low input voltages and as a standard rectifier at high input voltages. In this way, an input[…]

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Static d.c-d.c converter

A Type 555 timer and some passive components can provide a small converter to provide a negative output of 12 V at a few milliamperes. The 555 is connected as an astable with a rate of 125 kHz. Network C1-D2-05-D3 forms a cascade circuit that supplies a negative direct voltage. Since in the design it[…]

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Compact A-D converter

Although good and inexpensive integrated analogue to digital (A-D) converters are now readily available, it may be instructive to build one from discrete components. The present converter is based on a Type TLC274 IC, which contains four comparators. The output of these stages also forms the output of the converter. The problem with designing A-D[…]

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