This page is part of the N0NJY General Class self-study course for Technician operators upgrading to General.
Overview
General Class questions cover semiconductors, batteries, ferrite components, capacitor types, and basic
digital logic. Understanding these components helps you troubleshoot, repair, and modify amateur radio equipment.
Semiconductor Devices
Diodes: Allow current in one direction only. Forward voltage drop: approximately 0.6–0.7V
for silicon, 0.3V for germanium, 1.8–3.5V for LEDs depending on color.
PIV (Peak Inverse Voltage) is the maximum reverse voltage a diode can withstand without
breakdown. Rectifier diodes must be rated above the peak AC voltage they will see.
Zener Diode: Designed to operate in reverse breakdown at a specific voltage. Used for
voltage regulation — connected across a power supply output, it clamps the voltage to the zener voltage.
BJT (Bipolar Junction Transistor): Current-controlled. Small base current controls larger
collector current. Beta (β or hFE) is the current gain. Used as amplifiers and switches.
FET (Field-Effect Transistor): Voltage-controlled. Gate voltage controls drain current.
Very high input impedance. MOSFETs are common in RF power amplifiers because of their efficiency and linearity.
Ferrite Cores and Beads
Ferrite is a ceramic magnetic material with high permeability used in inductors, transformers, and chokes.
- Toroidal cores: Self-shielding — the magnetic field is confined within the core,
minimizing interaction with nearby components. Widely used in HF station equipment.
- Ferrite mix numbers: Different materials (Type 31, 43, 61, etc.) are optimized for
different frequency ranges. Type 31 is popular for HF common-mode chokes.
- Ferrite beads: Slipped over a cable, they act as a lossy inductor at RF frequencies,
attenuating common-mode RF currents. The simplest cure for RF-on-feedline problems.
Batteries
Lead-acid batteries: Nominal 12V system. Fully charged: 12.6V. Minimum discharge voltage
for maximum battery life: 10.5 volts. Discharging below 10.5V permanently damages the plates.
Charging releases hydrogen gas — explosive. Charge in a ventilated area.
Lithium Iron Phosphate (LiFePO4): Lighter and more energy-dense than lead-acid. Tolerates
deeper discharge. Requires a BMS (Battery Management System) and a charger designed specifically for lithium
chemistry. Do not charge with a lead-acid charger.
Digital Logic Gates
- AND: Output high only when ALL inputs are high
- OR: Output high when ANY input is high
- NOT (Inverter): Output is the opposite of the input
- NAND: AND with inverted output — output low only when all inputs are high
- NOR: OR with inverted output — output high only when all inputs are low
- XOR (Exclusive OR): Output high when inputs differ
Practice Questions
Q1 (G6A01) — What is the minimum allowable discharge voltage for maximum life of a standard 12-volt lead-acid battery?
- A. 10.5 volts
- B. 11.5 volts
- C. 12.0 volts
- D. 9.0 volts
Q2 (G6B01) — What is the peak inverse voltage rating of a rectifier?
- A. The maximum forward voltage before breakdown
- B. The maximum reverse voltage it can handle without breaking down
- C. The minimum forward current for conduction
- D. The reverse current when forward biased
Q3 (G6B05) — What is a common use for a ferrite bead?
- A. As a high-power resonant circuit element
- B. To reduce or eliminate RF interference on cables
- C. To increase power amplifier efficiency
- D. To block DC current in an RF circuit
Q4 (G6A09) — What is an advantage of the low internal resistance of nickel-cadmium batteries?
- A. Long life under trickle charge
- B. High energy density
- C. They can deliver high current pulses without significant voltage drop
- D. They are non-toxic and environmentally safe
Q5 (G6B03) — What is the output of a two-input NOR gate when both inputs are logic "0"?
- A. Logic "0"
- B. Logic "1"
- C. The inputs are added
- D. Undefined
Q6 (G6A11) — Which is an important characteristic of a toroidal core inductor?
- A. Large coupling to nearby components
- B. Requires a large air gap
- C. Self-shielding due to the magnetic field confined within the core
- D. High radiation of magnetic fields
Q7 (G6B07) — Which of the following describes a field-effect transistor?
- A. A current-controlled device where base current controls collector current
- B. A voltage-controlled device where gate voltage controls drain current
- C. A device that only operates in saturation
- D. A device requiring both forward and reverse biasing
Q8 (G6A03) — What is the approximate junction threshold voltage of a germanium diode?
- A. 0.7 volts
- B. 0.1 volts
- C. 0.3 volts
- D. 1.0 volts
Answer Key
- A — 10.5 volts is the minimum discharge voltage for lead-acid battery longevity
- B — PIV is the maximum reverse voltage a rectifier can withstand
- B — Ferrite beads reduce RF interference on cables
- C — Low internal resistance allows high current delivery without voltage drop
- B — NOR output is logic "1" only when both inputs are "0"
- C — Toroidal cores self-shield by confining the magnetic field within the core
- B — FETs are voltage-controlled devices
- C — Germanium diode forward voltage drop is approximately 0.3 volts