Physics & RF
B13 EM Spectrum & Military Bands — Study Guide
This guide covers EM Spectrum & Military Bands as part of Physics & RF. Start with the vocabulary, then try to answer each question before revealing the answer. Connect these facts to a real radio link or electrical circuit and practice the subject in the arcade when you are ready.
Acronyms first
| Term | Meaning |
|---|---|
| EMS | Electromagnetic Spectrum |
| ELF | Extremely Low Frequency |
| SLF | Super Low Frequency |
| ULF | Ultra Low Frequency |
| VLF | Very Low Frequency |
| LF | Low Frequency |
| MF | Medium Frequency |
| HF | High Frequency |
| VHF | Very High Frequency |
| UHF | Ultra High Frequency |
| SHF | Super High Frequency |
| EHF | Extremely High Frequency |
| SINCGARS | Single Channel Ground and Airborne Radio System |
| JTIDS | Joint Tactical Information Distribution System |
| IFF | Identification Friend or Foe |
| BLOS | Beyond Line of Sight |
| SATCOM | Satellite Communications |
| SAR | Synthetic Aperture Radar |
| NATO | North Atlantic Treaty Organization |
Key facts
How many RF bands (ELF through EHF) are listed?
11
Order these RF bands from LOWEST to HIGHEST frequency.
ELF → SLF → ULF → VLF → LF → MF → HF → VHF → UHF → SHF → EHF
Order the EM spectrum regions from LOWEST to HIGHEST frequency.
Radio waves → Microwaves → Infrared → Visible light → Ultraviolet → X-rays → Gamma rays
How many regions does the EM spectrum have?
7
EM wave energy is ____ proportional to frequency.
directly
There are sharp, universally agreed dividing lines between EM spectrum regions.
False
Radio waves are usually generated by an…
oscillator producing AC
A natural source of radio waves heard as static:
lightning
ELF range:
3–30 Hz
SLF range:
30–300 Hz
ULF range:
300 Hz–3 kHz
VLF range:
3–30 kHz
LF range:
30–300 kHz
MF range:
300 kHz–3 MHz
HF range:
3–30 MHz
VHF range:
30–300 MHz
UHF range:
300 MHz–3 GHz
SHF range:
3–30 GHz
EHF range:
30–300 GHz
HF wavelength range:
100 m to 10 m
VHF wavelength range:
10 m to 1 m
UHF wavelength range:
1 m to 10 cm
SHF wavelength range:
10 cm to 1 cm
EHF wavelength range:
1 cm to 1 mm
Scenario: a submarine deep underwater needs a message. Which band penetrates seawater best?
ELF
Scenario: you need global, beyond-line-of-sight comms bouncing off the ionosphere. Which band?
HF
Scenario: you're listening to AM broadcast radio. Which band?
MF
Scenario: tuning your car to FM radio, or airband. Which band?
VHF
Scenario: your phone is on 2.4 GHz Wi-Fi and cellular. Which band?
UHF
Scenario: your laptop uses 5 GHz Wi-Fi. Which band?
SHF
Scenario: a 5G mmWave tower. Which band?
EHF
Scenario: a legacy navigation beacon and time signals, plus sub comms. Which band?
VLF
Scenario: longwave broadcasting and military back-up navigation. Which band?
LF
Which band's performance is heavily affected by solar activity?
HF
In which band does rain fade start becoming relevant?
SHF
Which band has better building penetration than VHF in many cases and compact antennas?
UHF
At night, which band's skywave can dramatically extend range (AM)?
MF
Microwaves span roughly…
300 MHz to 300 GHz
Which region sits directly above microwaves?
Infrared
Infrared range:
~300 GHz to 430 THz
Visible light range:
~430 to 770 THz (700–390 nm)
Ultraviolet range:
~770 THz to 30 PHz (390–10 nm)
X-ray range:
~30 PHz to 30 EHz
Gamma ray range:
above ~30 EHz (below 0.01 nm)
Scenario: thermal cameras and missile seekers that track hot engines use…
infrared
Scenario: sterilization, forensics and fluorescence use…
ultraviolet
Scenario: airport security scanning and medical imaging of bones use…
X-rays
Highest-energy EM radiation, linked to nuclear/cosmic processes:
Gamma rays
Low frequency means…
long wavelength, large antennas, long reach
High frequency means…
short wavelength, more bandwidth, more directional, more LOS
Is a 30 MHz wave physically longer or shorter than a 300 MHz wave?
Longer (10 m vs 1 m)
As frequency increases, antenna size…
decreases
SINCGARS frequency range:
30–88 MHz
JTIDS / Link-16 frequency range:
960–1215 MHz
GPS frequencies:
1227.6 MHz and 1575.42 MHz
The F-35's fire-control radar operates in…
X-band
Military VHF Low Band:
30–88 MHz
Military VHF High Band:
108–174 MHz
Military UHF Low Band:
225–400 MHz
Military UHF High Band:
400–512 MHz
L-band:
1–2 GHz
S-band:
2–4 GHz
C-band:
4–8 GHz
X-band:
8–12 GHz
Ku-band:
12–18 GHz
K/Ka-band:
18–40 GHz
mmWave / W-band:
40–100 GHz
Scenario: squad-level tactical FM radios (SINCGARS) live in…
VHF Low Band
Scenario: GPS, IFF and Link-16 all live in…
L-band
Scenario: weather-resistant medium-range radar, ship and airport surveillance radar:
S-band
Scenario: missile seekers and naval gunnery fire-control radar with compact antennas:
X-band
Scenario: UAV data links, tactical SATCOM and SAR reconnaissance imaging:
Ku-band
Scenario: high-throughput SATCOM that is prone to rain fade:
K/Ka-band
Scenario: counter-drone and experimental imaging radar limited by heavy atmospheric absorption:
mmWave / W-band
Which uses broader categories for multinational compatibility?
NATO bands
U.S. and NATO both use which band letter structure?
A–M
Why is strict spectrum management important?
To avoid interference between users
Which band is MOST affected by the ionosphere: HF, VHF or UHF?
HF
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