GPS ranging signals — operational L-band frequencies The standard GPS system performs code and carrier ranging using how many L-band frequencies?

Introduction / Context:
GPS signals occupy L-band (approximately 1–2 GHz) for reliable propagation through the ionosphere and foliage. Classic ranging uses distinct L-band carriers and associated codes for positioning and ionospheric delay mitigation.

Given Data / Assumptions:

• Conventional GPS references the legacy core: L1 and L2.
• Modern signals (e.g., L5) exist but the canonical answer remains two L-band frequencies for standard dual-frequency operations.
• Range measurements imply code and carrier observations on these carriers.

Concept / Approach:
Dual-frequency ranging exploits the dispersive ionosphere: combining measurements on L1 and L2 removes first-order ionospheric error. Additional bands (like L5) enhance performance but the minimum standard for “dual-frequency GPS” is two L-band frequencies.

Step-by-Step Reasoning:

Verification / Alternative check:
Receiver specifications commonly cite L1/L2 tracking for survey and high-grade navigation; L1-only is single-frequency.

Why Other Options Are Wrong:

• 3 L-band or C-band options: Not representative of classic GPS; C-band is not used for GPS navigation signals.
• None of these: Incorrect since two L-bands are standard.

Common Pitfalls:
Confusing modern multi-band GNSS (adding L5/E5) with the minimum dual-frequency requirement.

Final Answer:
2 L-band frequencies