Section 2.1: Basic Components #
When you peek inside any radio equipment, you’ll find a fascinating array of electronic components working together in harmony. Let’s start our exploration with passive components - the workhorses of electronic circuits that don’t require an external power source to function.
Resistors: The Traffic Cops of Electronics #
Key Information: A resistor opposes the flow of current in any circuit (including a DC circuit).
Resistors are small cylindrical components with colored bands that indicate their resistance value. These color codes help electronics enthusiasts determine the component’s resistance.
Common applications in amateur radio include:
- Dividing voltages to protect delicate components
- Limiting current to sensitive parts
- Setting operating points in amplifier circuits
Capacitors and Inductors: The Energy Storage Twins #
Just as a battery stores energy chemically, capacitors and inductors also store energy—but in completely different ways. These components are like siblings: they complement each other while having their own unique characteristics.
Capacitors: Electric Field Energy Storage #
Key Information:
- A capacitor stores energy in an electric field
- A capacitor consists of conductive surfaces (usually metal plates) separated by an insulator. This physical structure is fundamental to how capacitors work and is frequently tested.
Capacitors come in various shapes and sizes, from tiny ceramic discs to large cylindrical types. Their capacity to store charge is measured in farads (F), though most radio circuits use microfarads (µF) or picofarads (pF).
In amateur radio, capacitors are used to:
- Smooth out fluctuations in power supplies (AC to DC converters)
- Block unwanted signals or noise, including keeping RF out of audio circuits
- Help select or tune specific frequencies in a circuit
Inductors: Magnetic Field Energy Storage #
Key Information:
- Inductors store energy in a magnetic field
- They are typically constructed as a coil of wire
- They are used with capacitors to make a resonant circuit
While capacitors store energy in an electric field, inductors store energy in a magnetic field that forms around the coil when current flows through it. This complementary relationship makes them perfect partners in radio circuits.
Inductors play important roles in radio circuits, including:
- Signal filtering
- Impedance matching
- Energy storage
Together, capacitors and inductors form the foundation of tuned circuits that select specific frequencies—the heart of radio technology.
Understanding Circuit Configurations #
Key Information: The fundamental differences between series and parallel circuits are:
- In series circuits, current is the same through all components
- In parallel circuits, voltage is the same across all components
These two circuit types behave very differently:
- Series Circuits: Components are connected end-to-end in a single path. If one component fails, the entire circuit stops functioning.
- Parallel Circuits: Components are connected across the same two points. If one path fails, current can still flow through the other paths.
Potentiometers: The Adjustable Resistors #
Key Information: A potentiometer is used to control resistance and is often used as a volume control.
A potentiometer is a variable resistor. As you turn the knob or slide the control, the resistance changes. In amateur radio, they are commonly used for:
- Volume control
- Adjusting transmit power levels
- Adjusting the squelch control
Switches: The Circuit Controllers #
Key Information:
- For your exam, you need to know about an SPDT (Single Pole, Double Throw) switch. This type of switch allows a single circuit to be switched between one of two other circuits.
- You will also need to be able to identify a SPST (Single Pole, Single Throw) switch on a circuit diagram.
A SPST switch is a simple on/off switch that controls one input. A SPDT switch is similar, but instead of merely turning the input on or off it switches it between two outputs. Think of an SPDT switch like a railroad track switch with one input track (the pole) that can connect to either of two output tracks (the throws). When you flip the switch, you’re choosing which output track the input will connect to.
Switches are described using two key terms:
- Poles: The number of separate circuits a switch can control
- Throws: The number of positions each circuit can be connected to
For example, in an SPDT switch:
- Single Pole: Controls one circuit
- Double Throw: Can connect that circuit to either of two positions
In amateur radio, switches are crucial for:
- Turning equipment on and off
- Selecting between different antennas
- Changing bands or modes on a transceiver
- Activating or deactivating specific features of a radio
Putting it together #
Understanding these passive components - resistors, capacitors, inductors, potentiometers, and switches - is crucial for grasping how electronic circuits work. They’re the building blocks that allow your radio equipment to function, controlling and shaping electrical signals in precise ways. As you continue your journey in amateur radio, you’ll encounter these components again and again, each time gaining a deeper appreciation for their roles in making radio communication possible.
Resistor