Unit 2 — Materials and Construction

TM-ANT-001 — Open Handout TM Chapter: Chapter 3 ELOs: Identify and gather all required materials; understand why each material is specified Estimated time: 20 minutes

Step 1: Read the TM

Open TM-ANT-001. Read Chapter 3 — Materials and Construction completely.

Then come back here.

Chapter 3 Content

  1. Use measured cuts based on wavelength formulas.
  2. Use common copper wire or tubing.
  3. Include a feedpoint structure that allows adjustment.
  4. Use a simple support structure to keep geometry consistent.

Material Selection

Review the full materials list in Chapter 3.

Before building, verify every item on the materials list. Key considerations: - Wire gauge affects conductor resistance and therefore efficiency — use the specified gauge or heavier - Coax type affects velocity factor, which changes electrical length vs. physical length - Ferrite core type (#43, #61, #67) is frequency-specific for matching transformers and chokes - Connector types affect impedance continuity — SO-239, N, BNC, and SMA each have frequency limits - Insulator material and placement affect wind loading and UV degradation

The materials list in Chapter 3 is the bill of materials for a tested, working antenna. Substitutions must be evaluated, not assumed equivalent.

Self-Check Questions

SC2-1. List the three most critical materials or components specified in Chapter 3. Why are they critical?

SC2-2. What wire gauge does Chapter 3 specify? What is the consequence of using a smaller gauge?

SC2-3. If Chapter 3 specifies coaxial cable, what type is called for? What is its velocity factor?

SC2-4. Does Chapter 3 specify a particular ferrite or core type? What is its application in this antenna?

SC2-5. What is the consequence of using a connector type outside its rated frequency range?

Answer Key

SC2-1. See Chapter 3. Identify items with specific part numbers, gauge specifications, or where substitution would change resonant frequency or impedance.

SC2-2. See Chapter 3. Smaller gauge = higher conductor resistance = lower efficiency and greater I²R losses.

SC2-3. See Chapter 3. Common types: RG-58 (0.66 VF), RG-8X (0.84), LMR-400 (0.85). Velocity factor changes electrical length: physical length = λ × VF.

SC2-4. See Chapter 3. Type #43 ferrite is general HF (1–50 MHz); #61 for upper HF/VHF; #67 for VHF. Wrong material means wrong impedance ratio at the operating frequency.

SC2-5. A connector used beyond its frequency rating introduces unpredictable impedance discontinuities, increasing reflected power and SWR.

Checkpoint

Before proceeding: - [ ] You have read Chapter 3 completely - [ ] You can name the critical materials from memory - [ ] You have sourced or confirmed availability of all required materials

→ Proceed to Unit 3