Unit 4 — Operating Procedures and Calculations

TM-TOOL-009 — 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-009. Read Chapter 5 — Operating Procedures and Appendix A completely.

Then come back here.

Chapter 5 Content

5-1 HF Reception with Upconverter

1. Enable bypass relay for frequencies ≥60 MHz (GPIO or front-panel switch). For 0.1–30 MHz: use upconverter path.
2. In SDR software: tune to 125 + f_HF (MHz). E.g., 40m = 7.15 MHz → tune SDR to 132.15 MHz.
3. Enable preselector for the band in use to reduce out-of-band interference. FM broadcast (88–108 MHz) causes severe IMD in RTL-SDR at HF; preselector eliminates this.

5-2 Adjusting Gain

1. Start with maximum attenuation (31.5 dB) on PE4302. Reduce in 6 dB steps until the noise floor drops and desired signals become visible.
2. Enable SPF5189Z LNA only for weak-signal work (<−100 dBm); for strong-signal environments (near broadcast transmitters), keep LNA off to avoid IMD.

Appendix A — Reference Formulas

Key Formulas Summary

Key mathematical relationships from Appendix A:

(See Appendix A in the TM)

Operating Notes

Chapter 5 specifies 5 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 SDR INTERFACES AND PRESELECTOR. List steps in order.

P4-2. From Chapter 5: what measurement setting or configuration produces the most accurate result with the SDR INTERFACES AND PRESELECTOR? 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