Unit 5 — Calibration and Verification

TM-TOOL-005 — Open Handout TM Chapters: Chapter 6, Chapter 7 ELOs: Calibrate the FIELD STRENGTH METER — CONSTRUCTION AND USE; verify performance against acceptance criteria; complete calibration log Estimated time: 45 minutes (actual lab work required)

Step 1: Read the TM

Open TM-TOOL-005. Read Chapter 6 — Calibration and Chapter 7 — Verification and Acceptance completely.

Then come back here.

Chapter 6 — Calibration Content

6-1 Absolute Calibration (Active and Digital FSMs)

1. Place a calibrated signal generator (or TinySA in generator mode) at a measured distance r from the FSM probe.
2. Set generator output to a known level P (dBm) into a calibrated antenna with known gain G (dBi). Compute E-field at distance r:

E (V/m) = sqrt(30 × P_watts × G_linear) / r

1. Record FSM reading at this field level. This is the calibration reference point. Adjust offset constant in firmware so that the CYD display shows the calculated E-field value.
2. Repeat at −10, −20, −30 dB relative levels using known attenuators. Verify linearity within ±1 dB across the range.

Chapter 7 — Verification Content

1. Passive FSM: connect a 0 dBm signal (from TinySA or signal generator) at 7 MHz via 50Ω coax. Meter should deflect to a repeatable scale reading. Deflection should decrease by approximately half (6 dB) when a 6 dB attenuator is inserted.
2. Digital FSM: apply −40 dBm, −50 dBm, −60 dBm. Verify CYD readings within ±2 dBm of expected values. (AD8307 typical accuracy: ±1 dB from −74 to +10 dBm.)
3. Log: date, version (passive/active/digital), calibration signal source, calibration power level, measured offset, 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: 30 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:

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