Unit 4 — Operating Procedures and Calculations
TM-GEAR-003 — Open Handout TM Chapters: Chapter 5, Appendix A ELOs: Install and operate the BALUNS AND UN-UNS — CURRENT AND VOLTAGE TYPES correctly; interpret performance data; compute derived quantities Estimated time: 30 minutes (includes 3–4 practice problems)
Step 1: Read the TM
Open TM-GEAR-003. Read Chapter 5 — Operating Procedures and Appendix A completely.
Then come back here.
Chapter 5 Content
- Mount the balun at the antenna feedpoint — not at the radio end. Feedpoint mounting minimizes the length of balanced feedline and the associated common-mode current problem.
- Weatherproof outdoor installations: coat all solder joints and exposed windings with two coats of polyurethane or Plasti-Dip. Wrap the core with self-amalgamating tape before mounting outdoors.
- Check SWR after installation. If SWR is higher than expected, the most common causes are: wrong impedance ratio for the antenna type, poor solder joint on the balun output terminals, or water ingress.
Appendix A — Reference Formulas
| Material | Best frequency range | Application |
|---|---|---|
| #31 ferrite | 1–300 MHz | Choke baluns (1:1); excellent CMC for all HF |
| #43 ferrite | 1–100 MHz | TLT baluns (4:1, 9:1); HF transformation |
| #61 ferrite | 10–200 MHz | 6M and VHF TLTs |
| #67 ferrite | 50–500 MHz | VHF/UHF choke baluns and TLTs |
| Air core | 50–1300 MHz | VHF/UHF choke (coax coil, no saturation risk) |
Key Formulas Summary
Key mathematical relationships from Appendix A:
(See Appendix A in the TM)
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 BALUNS AND UN-UNS — CURRENT AND VOLTAGE TYPES 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 BALUNS AND UN-UNS — CURRENT AND VOLTAGE TYPES? 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