Unit 4 — Operating Procedures and Calculations

TM-GEAR-013 — Open Handout TM Chapters: Chapter 5, Appendix A ELOs: Install and operate the POWER SUPPLIES — LINEAR, SWITCHING, AND FIELD PORTABLE correctly; interpret performance data; compute derived quantities Estimated time: 30 minutes (includes 3–4 practice problems)

Step 1: Read the TM

Open TM-GEAR-013. Read Chapter 5 — Operating Procedures and Appendix A completely.

Then come back here.

Chapter 5 Content

  1. Linear supply: allow 5 minutes warm-up before setting critical output voltage. Adjust the voltage trimmer to 13.8V (verified with DMM). Set current limit to 5A above the transceiver’s peak draw.
  2. SMPS: verify output voltage before connecting transceiver. Do not exceed rated current; SMPS enter fold-back current limiting and may drop voltage abruptly under severe overload.
  3. LiFePO4 portable: check pack voltage before operation. Below 12.4V (SOC ~20%), plan for recharging soon. Do not discharge below 10.0V.

Appendix A — Reference Formulas

For a linear supply, the voltage drop across series wiring: V_drop = I × R_wire For #14 AWG, R = 8.4 mΩ/ft (2.76 mΩ/m) At 30A over 3m of #14 AWG (6m round trip): V_drop = 30 × 0.00276 × 6 = 0.50V This means the bench at the end of 3m of #14 AWG gets 13.8 − 0.5 = 13.3V. Use #10 AWG for long runs or supply >20A.

Key Formulas Summary

Key mathematical relationships from Appendix A:

  • V_drop = I × R_wire
  • For #14 AWG, R = 8.4 mΩ/ft (2.76 mΩ/m)
  • V_drop = 30 × 0.00276 × 6 = 0.50V
  • This means the bench at the end of 3m of #14 AWG gets 13.8 − 0.5 = 13.3V.

Operating Notes

Chapter 5 specifies 3 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 POWER SUPPLIES — LINEAR, SWITCHING, AND FIELD PORTABLE 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 POWER SUPPLIES — LINEAR, SWITCHING, AND FIELD PORTABLE? 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