Know that communication with artificial satellites is mainly by microwaves: (a) some satellite phones use low orbit artificial satellites (b) some satellite phones and direct broadcast satellite television use geostationary satellites

3.3 Electromagnetic Spectrum

The electromagnetic spectrum is a range of all possible frequencies of electromagnetic radiation. It’s like a giant rainbow of waves, from very long radio waves to very short gamma rays. In physics we usually organise it by wavelength or frequency:

RegionWavelength (m)Frequency (Hz)Common Uses
Radio>1 m< 300 MHzAM/FM radio, TV broadcast
Microwave1 mm – 1 m300 MHz – 300 GHzSatellite comms, Wi‑Fi, radar
Infrared700 nm – 1 mmHeat, remote controlsIR cameras, night vision
Visible400 nm – 700 nm4×1014 – 7.5×1014 HzHuman vision, photography
Ultraviolet10 nm – 400 nm3×1015 – 3×1016 HzSterilisation, tanning
X‑ray / Gamma<10 nm>1016 HzMedical imaging, nuclear physics

Why Microwaves? 🚀

Microwaves are the perfect choice for satellite communication because:

  • They can travel long distances without much loss.

  • They can be focused into narrow beams, so many users can share the same satellite.

  • They’re not absorbed by the atmosphere as much as visible light or UV.

Satellite Orbits & Types

Satellites orbit the Earth at different altitudes, which affects how they communicate with us.

  1. Low Earth Orbit (LEO) – 160 km to 2 000 km above Earth. Think of it as a fast‑moving train that passes by every few minutes.

  2. Geostationary Orbit (GEO) – 35 786 km above Earth. This satellite stays fixed over one spot on the equator, like a lighthouse that never moves.

Satellite Phones & TV: How They Use Microwaves

Satellite phones and direct‑broadcast satellite TV use microwaves to send and receive signals. The key differences are the orbit type and the service they provide.

ServiceOrbit TypeTypical Frequency (GHz)Why It Works Here
Satellite Phone (LEO)Low Earth Orbit1.5 – 2.5 GHzFast hand‑off between satellites, lower latency.
Satellite Phone (GEO)Geostationary Orbit1.5 – 2.5 GHzFixed position means continuous coverage of a large area.
Direct‑Broadcast TV (GEO)Geostationary Orbit12 – 18 GHz (Ku‑band)High‑frequency allows large bandwidth for many channels.

Analogy: The Satellite “Post Office”

Imagine a global post office that uses invisible “mail trucks” (microwaves) to deliver messages. The post office can be:

  • Fast‑moving trucks (LEO) that deliver quickly but need many trucks to cover the whole world.

  • Stationary trucks (GEO) that stay in one place, so you can always call them from a fixed spot.

Both use the same invisible “mail trucks” (microwaves), but the choice of truck type depends on how fast you need the message and how wide the coverage area should be.

Key Take‑aways

  • Microwaves are the main part of the electromagnetic spectrum used for satellite communication.

  • Satellite phones can use LEO or GEO satellites, each with its own advantages.

  • Direct‑broadcast satellite TV almost always uses GEO satellites because they provide a stable, wide‑area signal.

  • Understanding the orbit type helps explain why some services are faster or cover larger regions.

Remember: the electromagnetic spectrum is like a toolbox, and microwaves are the versatile hammer that lets us talk to satellites no matter where we are on Earth! 🎯