Engineering Reference
RF Frequency Bands and Wavelength Reference
Non-regulatory RF band names and frequency-to-wavelength lookup with free-space, quarter-wave, half-wave, velocity-factor, and antenna-length boundaries.
- Reading Time
- 10 min
- Format
- Band and wavelength lookup
- Updated
- September 29, 2026
Classification, Not a Regulatory Allocation Table
The names below are broad engineering classifications. They do not grant permission to transmit. Always consult current national regulations, service allocations, equipment authorization, power, bandwidth and duty-cycle rules.
Radio-Frequency Band Names
| Band | Frequency range | Free-space wavelength | Name | Engineering boundary |
|---|---|---|---|---|
| VLF | 3-30 kHz | 100-10 km | Very low frequency | Propagation and antenna dimensions differ substantially from ordinary compact RF systems |
| LF | 30-300 kHz | 10-1 km | Low frequency | Band name is descriptive, not permission to transmit |
| MF | 300 kHz-3 MHz | 1 km-100 m | Medium frequency | Ground-wave and sky-wave behavior depend on environment and time |
| HF | 3-30 MHz | 100-10 m | High frequency | Ionospheric propagation can dominate practical links |
| VHF | 30-300 MHz | 10-1 m | Very high frequency | Antenna dimensions become practical fractions of a meter |
| UHF | 300 MHz-3 GHz | 1 m-100 mm | Ultra high frequency | PCB, enclosure and feed-line effects become increasingly important |
| SHF | 3-30 GHz | 100-10 mm | Super high frequency | Interconnect geometry, loss and connector transitions are critical |
| EHF | 30-300 GHz | 10-1 mm | Extremely high frequency | Material dispersion, atmospheric loss and fabrication tolerance require specialist analysis |
Frequency and Free-Space Wavelength
λ0 = c / f
Use c = 299,792,458 m/s. At 1 GHz, the canonical function gives 0.299792458 m.
| Frequency | Full wavelength | Quarter-wave | Half-wave |
|---|---|---|---|
| 100 kHz | 2997.92458 m | 749.481 m | 1498.962 m |
| 1 MHz | 299.792458 m | 74.948 m | 149.896 m |
| 10 MHz | 29.9792458 m | 7.495 m | 14.990 m |
| 100 MHz | 2.99792458 m | 749.481 mm | 1.498962 m |
| 433 MHz | 692.361 mm | 173.090 mm | 346.181 mm |
| 915 MHz | 327.642 mm | 81.910 mm | 163.821 mm |
| 2.4 GHz | 124.914 mm | 31.228 mm | 62.457 mm |
| 5.8 GHz | 51.688 mm | 12.922 mm | 25.844 mm |
| 10 GHz | 29.979 mm | 7.495 mm | 14.990 mm |
Wavelength in a Medium
| Quantity | Relationship | Meaning | Boundary |
|---|---|---|---|
| Propagation velocity | v = c × VF | Wave speed in the selected medium | Use a frequency-appropriate manufacturer value |
| Medium wavelength | λ = c × VF / f | Physical distance per cycle | VF = 1 only represents vacuum in the ideal relation |
| Quarter-wave | λ / 4 | 90-degree electrical-length reference | Loss, loading and discontinuities remain |
| Half-wave | λ / 2 | 180-degree electrical-length reference | Not automatically a finished dipole length |
| Physical radiator estimate | L = λ × fraction × shortening factor | First-pass antenna dimension | Tune or simulate in the final environment |
Worked Lookup Examples
| Case | Calculation | Result | Interpretation |
|---|---|---|---|
| 100 MHz in free space | 299,792,458 / 100,000,000 | 2.99792458 m | Quarter-wave is about 749.5 mm |
| 2.4 GHz in free space | 299,792,458 / 2.4e9 | 124.914 mm | Half-wave is about 62.457 mm |
| 1 GHz line, VF 0.66 | 0.299792458 × 0.66 | 197.863 mm | Quarter-wave line is about 49.466 mm before discontinuity effects |
| 433 MHz quarter-wave | c / 433e6 / 4 | 173.090 mm | Antenna implementation still requires tuning |
Common Errors
- Treating a band name as authorization to transmit.
- Using MHz as Hz without the 10^6 conversion.
- Using free-space wavelength for a cable or PCB line.
- Assuming one velocity factor at every frequency.
- Confusing wavelength with period.
- Treating quarter-wave as a universal final antenna length.
- Ignoring dielectric and enclosure loading.
- Ignoring conductor, feed and ground-plane effects.
- Using rounded c = 300,000,000 m/s where exact consistency matters.
- Assuming example frequencies are globally license-free.
- Applying far-field equations inside the antenna near field.
- Ignoring fabrication tolerance at millimeter wavelengths.
Support reference
FAQ
How do I calculate wavelength from frequency?
Use lambda = v / f. In vacuum use the exact speed of light; in a cable or dielectric use the propagation velocity specified for that medium.
What is the speed of light used in RF calculations?
The exact defined vacuum value is 299,792,458 meters per second. Air is close enough for many first-pass estimates but is not exactly vacuum.
Does an RF band name authorize transmission?
No. Band names classify frequency ranges. Authorization, power, bandwidth, duty cycle and equipment requirements depend on current rules in the operating jurisdiction.
Why is wavelength shorter in cable?
Electromagnetic propagation is slower in the cable dielectric. Wavelength equals free-space wavelength multiplied by the line's velocity factor.
What is a quarter-wave length?
It is one fourth of the wavelength in the relevant propagation medium. It is an electrical-length reference, not automatically a finished antenna dimension.
Can I make an antenna exactly one quarter of free-space wavelength?
That is only a starting estimate. End effects, conductor diameter, dielectric loading, ground plane, enclosure, feed and nearby objects shift resonance.
Why does higher frequency mean shorter wavelength?
At a fixed propagation velocity, frequency and wavelength are inversely related, so doubling frequency halves wavelength.
Are 433 MHz, 915 MHz and 2.4 GHz available everywhere?
Do not infer regulatory availability from a wavelength example. Permitted sub-bands and operating conditions vary by country and application.
Is wavelength the same as period?
No. Wavelength is distance per cycle, while period is time per cycle. Both are inversely related to frequency through different quantities.
When should I use velocity factor?
Use it for propagation in coaxial cable, PCB transmission lines and other media when the physical wavelength or electrical length matters.
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