Unit 4 — Operating Procedures and Calculations

TM-GEAR-017 — Open Handout TM Chapters: Chapter 5, Appendix A ELOs: Install and operate the ROLLER INDUCTORS — MOTORIZED VARIABLE INDUCTANCE correctly; interpret performance data; compute derived quantities Estimated time: 30 minutes (includes 3–4 practice problems)

Step 1: Read the TM

Open TM-GEAR-017. Read Chapter 5 — Operating Procedures and Appendix A completely.

Then come back here.

Chapter 5 Content

5-1 Homing Sequence

1. On power-up, the controller automatically homes: moves toward the home limit switch at 100 steps/sec until the switch opens; then backs off at 50 steps/sec until the switch closes again. This position is zero.
2. After homing, move to the last-used position (stored in NVS).

5-2 Setting Inductance

1. Enter the desired inductance in µH on the CYD or OLED display. The ESP32 looks up the corresponding step count in the calibration table and commands the motor.
2. For SWR-guided auto-tuning: the tuner controller (TM-GEAR-012) sends the target inductance via I2C or UART to the roller inductor controller.

Appendix A — Reference Formulas

Key Formulas Summary

Key mathematical relationships from Appendix A:

(See Appendix A in the TM)

Operating Notes

Chapter 5 specifies 4 operating steps.

Installation and operating discipline: - Always verify polarity and orientation before making connections — RF transformers and baluns are phase-sensitive - Route feedlines away from parallel conductors — parallel runs create mutual coupling that degrades isolation - Ground all exposed metalwork at a single chassis point — multiple grounds create loops - Record settings, frequencies, and power levels for every test — you need baseline data for comparisons

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 installation steps you would take to put the ROLLER INDUCTORS — MOTORIZED VARIABLE INDUCTANCE in service on a 40m (7.150 MHz) station. List steps in order.

P4-2. From Chapter 5: what installation or setup detail produces the best RF performance with the ROLLER INDUCTORS — MOTORIZED VARIABLE INDUCTANCE? What is the tradeoff if you omit or shortcut that step?

P4-3. Chapter 5 specifies an operating procedure for a specific use case. 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 mounting location → connect to feedline/antenna → verify polarity/orientation → apply power or signal → verify operation → record baseline.

P4-2. See Chapter 5. The most important installation detail is usually physical orientation, lead length, or ground bonding — the tradeoff if omitted is degraded isolation, increased SWR, or common-mode current leakage.

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 a degraded or unexpected result tells you about the installation

→ Proceed to Unit 5