Unit 2 — Construction and Materials
TM-GEAR-010 — Open Handout TM Chapter: Chapter 3 ELOs: Identify required components and materials; understand component selection criteria Estimated time: 20 minutes
Step 1: Read the TM
Open TM-GEAR-010. Read Chapter 3 — Equipment and Materials completely.
Then come back here.
Chapter 3 Content
| Component | Spec / Part | Purpose |
|---|---|---|
| Coax GDT arrestors | Polyphaser IS-B50LN-C2 or similar | Coax feedline protection |
| Entry panel | 6mm copper plate, 300×150mm | Single-point bonding bus |
| Ground rods | 8′ copper-clad steel (×2), connected by #6 AWG | Earth connection |
| Bonding straps | 1″ copper braid or 1/2″ copper strap | Panel to ground rod, equipment to panel |
| AC protector | Whole-house SPD (200A rated) | AC mains surge at service entrance |
| TVS diodes | P6KE68A (60V standby, 600W peak) | Secondary protection on control lines |
Component Selection
Review the equipment and materials list in Chapter 3 carefully.
Before building, verify every item on the materials list. Key considerations: - Use the specified component types — substitutions may affect performance or frequency coverage - Non-inductive components are required in RF circuits; standard wirewound resistors are unsuitable - Toroids and ferrite cores are frequency-specific; use the specified core material (#43, #61, #67, etc.) - Connector types affect impedance — match the specified connector to avoid SWR errors - Wire gauge and insulation type affect current capacity and voltage breakdown
The quality of your materials sets the ceiling on the component's performance.
Self-Check Questions
SC2-1. List the three most critical components or materials specified in Chapter 3. Why are they critical?
SC2-2. Does Chapter 3 specify non-inductive resistors? If so, where are they used and why does it matter?
SC2-3. What connector type(s) does Chapter 3 specify, and what is the frequency/power justification?
SC2-4. Does Chapter 3 specify a particular ferrite core material or type? What is its significance?
SC2-5. What would be the consequence of substituting a standard wirewound resistor for a non-inductive type in an RF application?
Answer Key
SC2-1. See Chapter 3. Identify items with specific part numbers, special materials, or critical tolerances — these are the ones that most affect performance.
SC2-2. See Chapter 3. Non-inductive types are used wherever standard inductive wirewound resistors would add series inductance that degrades high-frequency performance.
SC2-3. See Chapter 3. SO-239, N-type, BNC, and SMA each have different frequency and power ratings.
SC2-4. See Chapter 3. Ferrite #43 is for 1–100 MHz; #61 for 10–200 MHz; #67 for 50–500 MHz. Wrong material = wrong permeability = wrong coupling or suppression.
SC2-5. A wirewound resistor has several microhenries of series inductance. At HF and VHF, this adds inductive reactance proportional to frequency, destroying the resistor's value as a termination or load.
Checkpoint
Before proceeding: - [ ] You have read Chapter 3 completely - [ ] You can name the critical components from memory - [ ] You understand why non-inductive and correct ferrite materials are required
→ Proceed to Unit 3