Frequency allocations overview The lowest commonly used frequency band for satellite communications in the classical fixed-satellite service is approximately how many gigahertz (GHz)?

Introduction / Context:
Satellite links are assigned specific microwave bands. Historically, the fixed-satellite service used C-band (around 4/6 GHz) and later Ku-band (11/14 GHz) and Ka-band (20/30 GHz). The question asks for the lowest frequency broadly associated with satellite communications in this classical context.

Given Data / Assumptions:

• Classical FSS allocations (C-band upward) are intended.
• Options provided: 0.8, 3, 18, and 30 GHz.
• We select the closest representative threshold value.

Concept / Approach:
Traditional satellite textbooks treat the microwave window for FSS starting near a few gigahertz. While some systems use L-band around 1–2 GHz, the earliest mainstream commercial satcom is widely referenced from roughly 3–4 GHz upward. Among the options, 3 GHz best represents the lower end of “typical” satellite microwave operations.

Step-by-Step Solution:
Compare given values to canonical bands: C (4/6 GHz), Ku (12/14 GHz), Ka (20/30 GHz).Identify the lowest plausible marker among options that aligns with classical FSS: 3 GHz.

Verification / Alternative check:
A quick band ladder shows 3–4 GHz as the start of many reference tables for C-band downlinks, making 3 GHz the best rounding choice presented here.

Why Other Options Are Wrong:

• 0.8 GHz: below typical commercial FSS microwave allocations discussed in standard intros.
• 18 GHz and 30 GHz: these map to Ku/Ka upper portions, not the lowest.

Common Pitfalls:

• Confusing mobile-satellite L-band with the legacy FSS entry point.
• Assuming the exact downlink number; the question wants a representative lower bound.

Final Answer:
3 GHz