Wave Physics and Math
This fundamental equation governs the physical behavior of electromagnetic energy, stating that the speed of light equals wavelength multiplied by frequency.
What is c = λ × f?
This law dictates that the angle of incidence is equal to the angle of reflection when surface roughness is smaller than the incident wavelength.
What is Snell's Law of Reflection?
This radio band operates between 3 kHz and 30 kHz and is used by the military for submarine C2 because it can penetrate seawater up to 20 meters.
What is VLF (Very Low Frequency)?
This band operates between 30 MHz and 300 MHz, penetrates moderate foliage, and is used for military SINCGARS communications.
What is VHF (Very High Frequency)?
This ideal, non-existent antenna type features a radiation pattern that is perfectly identical in all directions.
What is an isotropic antenna?
According to the fundamental wave relationship, wavelength and frequency share this specific mathematical relationship.
What is an inverse relationship?
This term describes the irreversible conversion of electromagnetic energy into thermal or kinetic energy via molecular resonance.
What is Absorption?
This radio band spans from 300 kHz to 3 MHz, features moderate ground wave range during daylight, and is used for civilian AM broadcasting.
What is MF (Medium Frequency)?
Susceptible to hydrometeor attenuation (water in the air), this band spans 3 GHz to 30 GHz and is utilized by Starlink and active missile terminal seekers.
What is SHF (Super High Frequency)?
While directivity only describes an antenna's radiation pattern, this metric factors in real power losses due to physical circuit and material inefficiencies.
What is antenna gain?
This constant, approximately equal to 6.626 × 10⁻³⁴ Joule-seconds, is used in the Planck-Einstein relation to determine photon energy.
What is Planck's constant (h)?
This effect causes a wave to "bend" and change its phase velocity when transitioning across a boundary with differing refractive indices.
What is Refraction?
Operating between 3 and 30 MHz, this band refracts off the ionosphere to enable non-line-of-sight (NLOS) ranges.
What is EHF (Extremely High Frequency)?
This band features rapid atmospheric attenuation, zero foliage penetration, and requires the most power, operating from 30 GHz to 300 GHz.
What is EHF (Extremely High Frequency)?
This is the minimum number of sensors/antennas required to successfully locate an emitter using a 2D Time Difference of Arrival (TDoA) model.
What is three (3)?
Because a lower wavelength/higher frequency signal carries more energy, it requires this to transmit.
What is more power?
This overarching term refers to the total reduction in electromagnetic signal power over distance due to geometric spreading, scattering, and molecular absorption.
What is Attenuation?
Ground stations in this 30 kHz - 300 kHz band require high-power transmitters and tall vertical mast radiators due to a high atmospheric noise floor.
What is UHF (Ultra High Frequency)?
The military uses this 300 MHz - 3 GHz band for tactical secure data links, while civilians use it for 5G FR1 and GPS signals.
What is UHF (Ultra High Frequency)?
In Direction Finding (DF), the line from the antenna to the suspected emitter is known as this.
What is a line of bearing (LoB)?
Calculated with 32.44 + 20 x log10(R) + 20 x log10(f), this term describes the inherent attenuation caused by spherical spreading away from an isotropic antenna.
What is Free Space Path Loss (FSPL)?
This occurs when surface irregularities are comparable to or larger than the wavelength, causing the reflected light to scatter.
What is diffuse reflection (or scattering)?
These specific, annular dead spaces are produced by HF emissions, causing regions where signals cannot be received.
What are skip zones?
This specific physical phenomenon allows VHF signals to bend or pass over sharp terrain ridges.
What is knife's edge diffraction?
When adding capacitors or inductors to an AC circuit, this property is combined with resistance to create total impedance.
What is reactance?