Unit 5 — Calibration and Verification

TM-TOOL-001 — Open Handout TM Chapters: Chapter 6, Chapter 7 ELOs: Calibrate the ADF SYSTEMS — ANTENNA DIRECTION FINDING; verify performance against acceptance criteria; complete calibration log Estimated time: 45 minutes (actual lab work required)

Step 1: Read the TM

Open TM-TOOL-001. Read Chapter 6 — Calibration and Chapter 7 — Verification and Acceptance completely.

Then come back here.

Chapter 6 — Calibration Content

6-1 Watson-Watt Channel Balance

  1. Inject equal-amplitude, in-phase signal into both channels simultaneously from a common splitter. Verify RSSI within 0.3 dB.
  2. If unbalanced: add fixed attenuator pad (1–3 dB) to the stronger channel at the receiver input.
  3. Inject signal into NS channel only. Verify 90° + known bearing reads correctly. Repeat for EW channel.

6-2 Butler Matrix Beam Verification

  1. Place a known CW signal at each of the four expected beam-peak azimuths in turn (0°, 90°, 180°, 270°).
  2. Verify that the corresponding beam port shows maximum RSSI and adjacent ports show ≥3 dB lower level.
  3. Record beam-center azimuths. Apply offset table in software if beam centers deviate more than 5° from design.

Chapter 7 — Verification Content

After calibration, conduct a bearing verification test using a known-location transmitter:

  1. Position a low-power test transmitter at a measured azimuth from the array (use GPS or compass, to within ±1°).
  2. Take 20 bearing readings; compute mean and standard deviation.
  3. Acceptance criterion: mean error <5°, standard deviation <3°.
  4. If failed: re-check element spacing, coax phase lengths, and channel balance.
  5. Record results in calibration log: date, frequency, test azimuth, mean bearing, standard deviation, operator.

Calibration vs. Verification — Distinction

Calibration (Chapter 6): active adjustments to bring the tool within specification. You are permitted to adjust, tweak, and repeat until the criterion is met.

Verification (Chapter 7): independent confirmation that the calibration succeeded. No adjustments are permitted during verification. If a verification check fails, you return to Chapter 6, not to Chapter 7.

Acceptance Criterion

A criterion found in Chapter 6: 0.3 dB. Confirm the exact criterion in the TM.

Write the exact criterion from the TM here before you start the lab:

Lab Checklist

Work through each item in sequence. Do not skip steps.

  • [ ] All required equipment gathered and ready
  • [ ] Equipment warmed up per TM requirements
  • [ ] All Chapter 4 setup steps verified complete
  • [ ] Chapter 6 calibration performed (all steps)
  • [ ] Calibration criterion met (recorded below)
  • [ ] Chapter 7 verification performed (all steps, no adjustments)
  • [ ] All verification criteria passed
  • [ ] Calibration log entry completed

Calibration Log Entry

  • [ ] Date
  • [ ] Equipment used
  • [ ] Measurements taken
  • [ ] Results vs. criteria
  • [ ] Operator name

Record your results:

Item Measured Value Acceptance Criterion Pass/Fail
(from Ch 7)
(from Ch 7)
(from Ch 7)

Self-Check Questions

SC5-1. What is the acceptance criterion for this calibration (from Chapter 7)?

SC5-2. During verification, one reading fails. What is the correct action per the TM?

SC5-3. List the items required in a calibration log entry per Chapter 7.

SC5-4. What is the difference between calibration and verification in this context?

SC5-5. If the tool passes all Chapter 7 checks, what does that tell you about its current state?

Answer Key

SC5-1. See Chapter 7. The criterion is stated as a specific value with units.

SC5-2. Stop verification. Return to Chapter 6 and re-calibrate. Diagnose the cause before re-adjusting.

SC5-3. See Chapter 7, last numbered step. The log items are listed there.

SC5-4. Calibration allows adjustments; verification does not. Verification is independent confirmation.

SC5-5. It tells you the tool is performing within its specified accuracy at this time. It does not tell you how long it will remain in calibration — periodic re-calibration is required.

Checkpoint

You are ready for the final assessment when you can: - [ ] State the acceptance criterion from memory - [ ] State the difference between calibration and verification - [ ] State the required log items from memory

→ Proceed to Final Assessment