Unit 1 — Theory of Operation

TM-GEAR-001 — Open Handout TM Chapter: Chapter 2 ELOs: Understand the operating principle of the ANTENNA SWITCHES — MANUAL, MOTORIZED, AND AUTO-BAND; identify key specifications Estimated time: 20 minutes

Step 1: Read the TM

Open TM-GEAR-001. Read Chapter 2 — Theory of Operation completely.

Then come back here.

Chapter 2 Content

2-1 RF Switching Requirements

An antenna switch routes a single transmitter/receiver to one of N antennas without significant signal loss or impedance mismatch. Key parameters:

• Insertion loss: Signal attenuation through the selected path. Target 2-2 Relay Types

Mechanical relays (Omron G2RL, Panasonic TQ2) provide low insertion loss but are limited to ~10 MHz switching rate and wear over millions of cycles. They are appropriate for all antenna switching applications. PIN diode switches (MA4P504, HSMP-3814) switch in nanoseconds and have no wear, but require bias current and have higher insertion loss at HF.

2-3 Auto-Band Switching

The auto-band switch monitors the transceiver's CI-V (Icom) or CAT (Yaesu/Kenwood) bus to determine the operating frequency. A lookup table maps frequency ranges to antenna ports. On a band change, the ESP32 toggles the correct relay within 50 ms — before the first transmitted audio reaches the antenna.

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 ANTENNA SWITCHES — MANUAL, MOTORIZED, AND AUTO-BAND 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 ANTENNA SWITCHES — MANUAL, MOTORIZED, AND AUTO-BAND 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 ANTENNA SWITCHES — MANUAL, MOTORIZED, AND AUTO-BAND - The primary loss or degradation source(s) - At least one key specification with its value

→ Proceed to Unit 2