Final Assessment — HELICAL CALIBRATION (HOMEBREW)

TM-ANT-003 — Open Handout Course: TM-ANT-003 Reference: TM-ANT-003 handout Questions: 15 Passing score: 13/15 (87%). All calculation questions (Q6–Q9) must be correct. Time limit: 20 minutes Notes: Closed handout. No references during the assessment.

Questions

Q1. What is the operating principle of the HELICAL CALIBRATION (HOMEBREW)? State it in one sentence using technical terms.

Q2. Calibration compares the Helical response to a known reference. For antennas, the reference comes from physical dimensio Explain the significance of this principle for antenna performance.

Q3. What determines the resonant frequency of the HELICAL CALIBRATION (HOMEBREW)? Name the primary physical parameter(s) and state whether increasing that parameter raises or lowers resonant frequency.

Q4. Chapter 3 specifies particular materials for the HELICAL CALIBRATION (HOMEBREW). Name two materials where a substitution would change RF performance and explain the effect.

Q5. What is the first step of the Chapter 4 assembly procedure? Why must the steps be performed in the specified order?

Q6. [Calculation] Using the formula from Appendix A (the primary length formula from Appendix A): Compute the element length for a frequency 10% higher than the design frequency. Show all work and state the result with units.

Q7. [Calculation] Using the formula: a second formula from Appendix A Calculate a result for a specific antenna scenario. Show all work.

Q8. [Calculation] Your NanoVNA shows minimum SWR at 7.350 MHz. The design frequency is 7.150 MHz. Compute the percentage deviation and the required length correction. Show all work.

Q9. [Calculation] Compute the reflected power percentage for SWR = 2.5:1. Formula: RP(%) = ((SWR − 1)/(SWR + 1))² × 100. Show all work.

Q10. During Chapter 5 calibration, your SWR at the design frequency is 3.8:1. What does Chapter 6 direct you to do? What adjustment direction is required if resonance is above the design frequency?

Q11. What is the SWR acceptance criterion stated in Chapter 7 for the HELICAL CALIBRATION (HOMEBREW)? State it exactly: value and condition.

Q12. What is the difference between the Chapter 6 tuning procedure and the Chapter 7 verification procedure? Which permits adjustments?

Q13. During Chapter 7 verification, SWR measures 2.6:1. You re-trim the element and re-measure: SWR is now 1.7:1. Is the verification valid? What is the correct action?

Q14. List four required items in a verification log entry per Chapter 7.

Q15. After completing Chapter 7 verification with all checks passing, what can you conclude about the HELICAL CALIBRATION (HOMEBREW)? What can you NOT conclude?

— Turn page for answer key —

Answer Key

All answers directly verifiable from TM-ANT-003.

A1. See TM §2-1. The answer is the first substantive statement of Chapter 2. TM ref: §2-1

A2. See TM §2-1. The significance is stated in Chapter 2, usually in terms of bandwidth, efficiency, or pattern. TM ref: §2-1

A3. See Chapter 2. For wire antennas, physical length is primary. Loading elements (coils, capacitors) change effective electrical length. Longer = lower resonant frequency. TM ref: Ch. 2, App. A

A4. See Chapter 3. Critical materials include wire gauge (affects conductor loss), coax type (velocity factor changes matching section length), and ferrite type (affects impedance transformation at frequency). TM ref: Ch. 3

A5. See Chapter 4, step 1. The sequence exists because each step has physical or electrical dependencies on prior steps. TM ref: Ch. 4

A6. Formula: the primary length formula from Appendix A. Frequency 10% higher = element 10% shorter. Confirm your result is physically plausible (shorter wire = higher frequency). TM ref: App. A

A7. Formula: a second formula from Appendix A. Show substitution, arithmetic, result with units. TM ref: App. A

A8. Deviation = (7.350 − 7.150) / 7.150 × 100 = 2.8% above design frequency. Antenna is electrically short. Required correction: lengthen element by approximately 2.8%. TM ref: App. A, Ch. 6

A9. RP(%) = ((2.5 − 1)/(2.5 + 1))² × 100 = (1.5/3.5)² × 100 = (0.4286)² × 100 = 18.4% reflected. TM ref: App. A

A10. See Chapter 6. High SWR at design frequency with resonance above → antenna is short → lengthen the radiating element. Chapter 6 specifies the trim procedure. TM ref: Ch. 6

A11. Criterion: the SWR criterion stated in Chapter 7. Check your wording against Chapter 7 — numeric value and conditions must match exactly. TM ref: Ch. 7

A12. Tuning (Ch. 6) allows active adjustments to bring the antenna within specification. Verification (Ch. 7) confirms the result and allows no adjustments. Only tuning permits adjustments. TM ref: Ch. 6, Ch. 7

A13. No — the verification is invalid. Making adjustments during verification invalidates it. Correct action: return to Chapter 6 tuning with the current element length, complete tuning, then restart the full Chapter 7 verification with no further adjustments. TM ref: Ch. 7

A14. See Chapter 7, final steps. Required items typically include: date, antenna type, operating frequency, height/orientation, SWR measurement, pass/fail determination, operator name. TM ref: Ch. 7

A15. You CAN conclude: the antenna meets the specified SWR and resonance criteria at this time, at this location and height, in this orientation. You CANNOT conclude: performance will be identical at a different site, height, or orientation; or that the antenna will remain in spec without re-verification. TM ref: Ch. 7

Score Routing

Question → Unit map: Q1–Q3 → Unit 1 (Theory); Q4–Q5 → Units 2–3 (Materials/Assembly); Q6–Q9 → Unit 4 (Calculations); Q10 → Unit 4; Q11–Q15 → Unit 5 (Verification).