The Basic lessons · Station assembly, practice and safety · B-003-017

Power Supplies and Safe DC Connections

Learn how to choose and connect power supplies to avoid signal noise and equipment damage. Understand why wire size, fuse placement, and supply type matter for clear transmissions.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-003-017.

What this subsection asks

• You construct a simple DC power supply using a transformer, rectifier and filter capacitor. If you use the supply to power a CW transmitter, what problem with signal quality could it cause?
• What device converts 120 volts AC to 12 volts DC?
• When selecting a 13.8 V DC power supply for a transceiver, what design specification is most important?
• Compared to a switching (switch mode) power supply, why may a linear power supply be preferred?
• In a mobile installation, why should the fuse in the DC line to the transceiver be located as near to the battery as possible?
• Apart from efficiency, what is one advantage of a switching (switch mode) power supply over a linear power supply?
• Why are heavy-gauge wires used for a 100-watt transceiver's DC power connection?
• What are the nominal power-line voltages supplied to homes?
• Your transceiver's user guide suggests limiting the voltage drop to 0.5 volts and the vehicle battery is 3 metres away. Given the losses listed below at the required current of 22 amperes, which minimum wire gauge must you use?
• Why must the positive lead from the vehicle battery to your transceiver be fused?
• You have a very loud low-frequency hum appearing on your transmission. In what part of the transmitter would you first look for the trouble?