Unit 4 — Operating Procedures and Calculations
TM-TOOL-004 — Open Handout TM Chapters: Chapter 5, Appendix A ELOs: Execute operating procedure; interpret readings; compute derived quantities Estimated time: 30 minutes (includes 3–4 practice problems)
Step 1: Read the TM
Open TM-TOOL-004. Read Chapter 5 — Operating Procedures and Appendix A completely.
Then come back here.
Chapter 5 Content
- Always confirm dummy load is connected before transmitting. A momentary key-down into open coax can damage the final transistor.
- For CW/SSB testing: key down for ≤10 seconds, off for ≥30 seconds until thermal equilibrium is reached (approximately 15 minutes at full power).
- For the oil loads: after extended use, check for oil seepage at the lid seal. If oil temperature exceeds 70°C (hot to the touch), reduce duty cycle or allow cooling.
- Never use the 100W dry load above 100W continuous; use the oil loads for higher power or high duty cycle modes (FT8, WSPR, digital).
Appendix A — Reference Formulas
| Ambient temp | 100W load max | 500W load max | 1 kW load max |
|---|---|---|---|
| 25°C | 100W continuous | 500W continuous | 1000W continuous |
| 40°C | 70W continuous | 350W continuous | 700W continuous |
| 50°C | 50W continuous | 250W continuous | 500W continuous |
Key Formulas Summary
Key mathematical relationships from Appendix A:
(See Appendix A in the TM)
Operating Notes
Chapter 5 specifies 4 operating steps.
Measurement discipline: - Always warm up the tool and reference sources before taking readings - Multiple readings improve accuracy — use 3–5 readings and average them - Record every reading with frequency, power level, and settings - A result that seems wrong almost always means a setup error, not a failed tool
Practice Problems
Work these before reading the answer key below.
P4-1. Using the operating procedure from Chapter 5 and the formulas from Appendix A: State the measurement steps you would take to characterize a 40m (7.150 MHz) dipole antenna using the RF DUMMY LOADS — CONSTRUCTION AND USE. List steps in order.
P4-2. From Chapter 5: what measurement setting or configuration produces the most accurate result with the RF DUMMY LOADS — CONSTRUCTION AND USE? What is the tradeoff if you use a less accurate setting?
P4-3. Chapter 5 specifies an operating procedure for a specific measurement scenario. State the first three steps of that procedure from memory.
P4-4. Appendix A gives a formula for computing a result from measured values. Pick one formula and compute a worked example using made-up but realistic values. Show all work.
Answer Key — Practice Problems
P4-1. Compare your list to Chapter 5. Steps should include: select range/mode → connect antenna → apply signal or enable source → adjust for null/maximum → read and record → compute result.
P4-2. See Chapter 5. The most accurate setting is usually the narrowest bandwidth or highest resolution, at the cost of longer measurement time or reduced range.
P4-3. See Chapter 5, steps 1–3. Copy exactly then close the TM and state from memory.
P4-4. See Appendix A for the formula. Your arithmetic is correct if your result has the right units and is physically plausible.
Checkpoint
Before proceeding: - [ ] You can state the operating procedure from memory (at least the first 5 steps) - [ ] You can compute the derived quantity from Chapter 5 / Appendix A without looking - [ ] You understand what "an unexpected result" tells you about setup
→ Proceed to Unit 5