Unit 2 — Equipment and Test Setup
TM-CAL-002 — Open Handout TM Chapter: Chapter 3 ELOs: Identify required equipment; understand test configuration Estimated time: 20 minutes
Step 1: Read the TM
Open TM-CAL-002. Read Chapter 3 — Materials and Construction completely.
Then come back here.
Chapter 3 Content
3-1. BILL OF MATERIALS
| Qty | Item | Specification | Notes |
|---|---|---|---|
| 1 | GPS receiver module | NEO-M8N preferred; NEO-6M acceptable | Must have 1PPS output pin |
| 1 | GPS patch antenna | Active, 25×25 mm or 35×35 mm | Magnetic mount for mobility |
| 1 | SMA or IPEX cable | 50 Ω, length as needed | GPS antenna to module |
| 1 | 5 V power supply | 100 mA minimum, clean DC | USB supply acceptable |
| 1 | SMA/BNC adapter | For 1PPS output | Or BNC connector direct |
| 1 | 50 Ω BNC cable | RG-58, 0.5–1 m | 1PPS to counter/scope |
3-2. LEVEL SHIFTING
If the GPS module outputs 3.3 V logic and the counter requires 5 V TTL, a simple level-shift circuit is needed.
Voltage divider for 5V to 3.3V (GPS antenna power only)
Not required for 1PPS: most counters accept 3.3 V on TTL input
NOTE: The NanoVNA, TinySA Ultra, and most modern frequency counters accept 3.3 V logic on TTL inputs. No level shifting is required for these instruments.
Equipment Readiness
Review the equipment list in Chapter 3 carefully.
Before beginning any calibration, verify every item on the equipment list is: - Present and in working order - Within its own calibration period (do not calibrate with an uncalibrated reference) - Set up per the configuration specified in Chapter 3
The reference quality is the ceiling on your calibration quality. A reference with unknown accuracy produces a calibration with unknown accuracy.
Self-Check Questions
SC2-1. List the three most important pieces of equipment specified in Chapter 3.
SC2-2. What reference standard(s) does the TM specify for this calibration?
SC2-3. Does Chapter 3 specify any warm-up time or settling requirement? If so, state it.
SC2-4. What is the test configuration? (How is the equipment connected or arranged?)
SC2-5. What would be the consequence of using a reference standard that is itself out of calibration?
Answer Key
SC2-1. See Chapter 3 equipment table or list. Identify the three items that appear first or are marked most critical.
SC2-2. See Chapter 3. The reference standard is the source of known-good values used to check the instrument under test.
SC2-3. See Chapter 3. Warm-up time is often specified for instruments that use oscillators or amplifiers — they need thermal stabilization before measurements are valid.
SC2-4. See Chapter 3. Describe the connection or arrangement in your own words, then verify against the TM.
SC2-5. The calibration error of the reference propagates directly into your calibration result. If the reference is 5% off and you do not know it, your calibration will also be 5% off — and you will not know that either.
Checkpoint
Before proceeding, you must be able to: - List the required equipment from memory - State the reference standard and its specified accuracy
→ Proceed to Unit 3