This is Phase 1 of a short series that establishes the electromagnetic spectrum foundation every EW practitioner needs. The goal is practical clarity. I will cover the physics basics you will rely on when thinking about antennas, propagation, signature management, jamming tradeoffs, and how spectrum is carved up and regulated.

What the electromagnetic spectrum is and the core equations Electromagnetic energy is described two ways that matter for EW: frequency and wavelength. Frequency is the number of oscillations per second and is measured in hertz. Wavelength is the physical distance between successive peaks in the wave. Those two are linked by the speed of light c through the simple relation c = lambda times f. Use that equation to move between frequency and wavelength when sizing antennas or estimating propagation.

A related relation ties frequency to energy. The energy of a single photon is E equals h times f where h is Planck’s constant. For EW this relation mostly matters conceptually because higher frequency signals generally carry more energy per photon and tend to behave differently in the environment.

How the spectrum is organized and common band uses Engineers and regulators break the spectrum into named bands. Roughly speaking you will see these labels in technical and policy documents: LF, MF, HF, VHF, UHF, SHF, and EHF. Each band has typical uses that drive EW tradeoffs:

  • HF (roughly 3 to 30 MHz) supports long range beyond–line–of–sight comms and skywave propagation via the ionosphere. That makes HF useful for long distance fixed or maritime links but harder for high data rates.
  • VHF and UHF (tens to hundreds of MHz up to about 1 GHz) are the tactical radio and broadcast workhorses. They are largely line of sight at short ranges and can diffract around obstacles better than higher frequencies.
  • SHF and EHF (gigahertz region into tens of GHz) host most radar, point to point microwave links, satellite uplinks, and growing millimeter wave data links. These bands give high bandwidth and resolution but require precise pointing and suffer atmospheric absorption at the highest frequencies.

Propagation basics that determine EW choices Propagation behavior is the single most important practical concept for EW. Expect these broad regimes:

  • Groundwave and surface propagation dominate at lower frequencies and support stable long distance coverage over conductive surfaces.
  • Skywave or ionospheric reflection makes HF useful for long range, but the ionosphere is variable and time of day dependent.
  • Line of sight dominates above VHF for most tactical links and all microwave communications. Path clearance and antenna height determine reach.
  • Atmospheric and rain absorption increase with frequency. Above roughly 10 GHz you start to plan for moisture, oxygen, and rain losses when sizing links or planning radar performance.

Antennas, wavelength and practical rules of thumb Antenna physical size scales with wavelength. Low frequency work requires larger elements or deployable structures. At microwave frequencies small antennas with high gain become practical. Beamwidth, aperture area, gain, and polarization are the levers you manipulate in EW design. When you think about jamming or spoofing a radio or radar, the antenna geometry on both ends tells you whether a broad area broadcast or a narrow high power beam is the correct instrument.

Spectrum management and the regulatory environment In civilian domains the electromagnetic spectrum is managed and allocated by national authorities and international bodies. In the United States the NTIA coordinates federal spectrum use while the FCC handles most non federal allocations. Spectrum allocation charts show which bands are reserved for radio navigation, broadcasting, mobile networks, satellite services, scientific uses, and unlicensed activity such as various ISM channels. These allocations constrain what is legal to transmit and where. If you are experimenting or developing EW techniques outside a controlled lab, know the legal allocations and licensing rules before you generate energy on air.

Where electronic warfare fits into the spectrum picture Electronic warfare is the set of activities that deliberately employ, deny, or protect the electromagnetic environment to achieve military objectives. EW is commonly divided into three functional lines: electronic attack, electronic protection, and electronic support. In practical terms those roles map to jamming and deception, countermeasures and hardening, and sensing plus signal collection and direction finding. Understanding which part of the spectrum a target system uses is the first step in choosing the technique to detect, deny, or protect that system.

Implications for jamming and countermeasure design From a tactical standpoint the following items are repeatedly decisive:

  • Frequency and bandwidth. Wider bandwidth targets need more power to jam uniformly or require more sophisticated swept or noise techniques. Narrowband systems can be overwhelmed more efficiently if you can concentrate power.
  • Propagation and reach. A jamming transmitter that works at UHF in urban canyons may be useless at HF where ionospheric propagation dominates. Conversely HF jammers can affect long distance links if they are designed for skywave coupling.
  • Antenna and polarization match. Effective interference requires consideration of antenna gain patterns and polarization alignment.
  • Legal and collateral risks. Many civilian systems share bands with military users. Indiscriminate transmissions can cause harmful interference to public safety, navigation, and commercial infrastructure. Refer to national allocation tables and coordinate where required.

Tools, measurement and learning path Start with measurement. A spectrum analyzer and a well configured software defined radio will teach more than slides. Learn to read a spectrum waterfall, identify modulation signatures, and estimate bandwidth and occupied power. Combine lab testing with open source documentation on band use and national allocation charts. For practical EW labs keep transmissions contained and get proper authorization for anything that radiates outside shielded test ranges.

Closing and what comes next If you understand the simple physics, the band roles, propagation regimes, and the regulatory overlay you have the toolkit to begin mapping real targets and systems. Phase 2 will build on this and cover modulation signatures, link budgets, and the common sensing techniques used in electronic support. Keep experiments legal, document your measurements, and let propagation and antenna constraints guide your tactical choices.