Unit 1 — Theory of Operation

TM-GEAR-013 — Open Handout TM Chapter: Chapter 2 ELOs: Understand the operating principle of the POWER SUPPLIES — LINEAR, SWITCHING, AND FIELD PORTABLE; identify key specifications Estimated time: 20 minutes

Step 1: Read the TM

Open TM-GEAR-013. Read Chapter 2 — Theory of Operation completely.

Then come back here.

Chapter 2 Content

2-1 Linear Regulated Supply

A transformer (120V/18V, 40VA) followed by a full-wave bridge rectifier and large filter capacitor (10,000–20,000 µF) provides unregulated DC. A series-pass transistor (multiple 2N3055 or IRF540 in parallel) regulated by an op-amp error amplifier maintains constant output voltage. Linear supplies have extremely low ripple and noise (2-2 Switching SMPS

An SMPS converts AC to DC at high frequency (50–500 kHz), allowing much smaller transformers. Efficiency: 85–92%. The PWM controller (UC3842 or SG3525) regulates output voltage by adjusting duty cycle. EMI filtering is critical for SMPS; they generate conducted and radiated interference that can degrade receiver performance.

2-3 Metering and Protection

A metering module uses a series current shunt (100 A / 75 mV shunt) and a voltage divider to display voltage and current on a CYD display. Over-current protection uses a comparator circuit to trip a power relay if current exceeds the set limit (adjustable 0–30 A via a trimpot).

Why Theory Matters

You cannot build or use RF gear correctly without understanding how it works. Theory tells you: - What the component does and how it produces that effect - What the sources of loss, distortion, or error are — so you can recognize and minimize them - What the valid operating range is — frequency, power, impedance — so you stay within specifications - How to interpret results or system behavior that doesn't match expectations

If a component doesn't perform as expected, theory is where you look first.

Self-Check Questions

SC1-1. In one sentence, state the operating principle of the POWER SUPPLIES — LINEAR, SWITCHING, AND FIELD PORTABLE as described in Chapter 2.

SC1-2. What does Chapter 2 identify as the primary source(s) of loss or degradation in performance?

SC1-3. What key specification(s) (frequency range, power rating, insertion loss, impedance ratio) does the TM state?

SC1-4. What does Chapter 2 say the POWER SUPPLIES — LINEAR, SWITCHING, AND FIELD PORTABLE cannot do — what are its limitations?

SC1-5. List two formulas or relationships from Chapter 2 that govern the component's behavior.

Answer Key

SC1-1. See TM §2-1. Compare your sentence to the first substantive paragraph of Chapter 2.

SC1-2. See Chapter 2. Look for language about loss mechanisms, parasitic effects, frequency limits, or power constraints.

SC1-3. See Chapter 2. Look for numbers with units: %, dB, Hz, Ω, W, V.

SC1-4. See Chapter 2 and Chapter 1. Limitations are often stated as frequency range, power handling, or impedance range.

SC1-5. See Chapter 2. Equations or proportionality statements are the relationships that govern the component.

Checkpoint

Before proceeding, state without looking: - The operating principle of the POWER SUPPLIES — LINEAR, SWITCHING, AND FIELD PORTABLE - The primary loss or degradation source(s) - At least one key specification with its value

→ Proceed to Unit 2