Photograph of an electric meter too close to a bed and sleeping area - high EMF will be measured if quite close to electrical meters Definitions of Terms for RF and EF Electromagnetic Fields
Table of Electromagnetic Radiation Frequencies by Type of Source

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Definitions & table of signal & other frequencies from lowest to highest:

This article defines and explains electromagnetic field (EMF) or electro-magnetic radiation EMR and related terms such as EMF, radio frequency - RF, hertz or cycles, megahertz, medium frequency MF, very high frequency VHF, ultra high frequency UHF, megahertz MHz, gigahertz GHz, terahertz THz .

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Definitions & Names of Different Radio Frequency or Electromagnetic Frequency Ranges: RF and EF Electromagnetic Fields

EMFfield sketchBefore buying test equipment to measure the strength of electromagnetic fields, readers should review this article to be sure that they understand the types of electical fields that exist, the typical sources of different types of electromagnetic fields (power lines, AM and FM radio towers, cell towers, other equipment), and thus the type of test equipment that would be used to assess electrical field strength.

Discussed here: What kinds of radio frequency waves are there, what are EMF, RF, hertz, megahertz, MF, VHF, UHF, MHz, GHz, THz ? Definition of ELF EMF VHF UHF - Definitions of electromagnetic frequency ranges & electromagnetic radiation types & sources.

Table of Electromagnetic Radiation Frequencies by Wavelength and Frequency - Table of electromagnetic fields by source type: cell towers, cell phones, power lines, radio towers, home appliances, CRTs, computers, etc. Links to EMF measurement explanations, procedures, worksheets, instruments & advice.

Electromagnetic fields, or EMFs are invisible lines of force created whenever electricity is generated or used. EMFs are produced by power lines, electric wiring, and electric equipment and appliances. The frequency of EMFs is measured in hertz (Hz, or cycles per second).

People are exposed to both electric and magnetic fields, but scientists are most concerned about magnetic fields. This fact sheet deals only with magnetic fields that have frequencies near 60 Hz the frequency of electric power in North America.

Static magnetic field around a bar magnet.

Health professionals, epidemiological experts, and in the case of EMF, electrical engineers can offer competent, expert advice which should be considered before any costly or risky actions are taken regarding this or other environmental topics. Use information at this website at your own risk.

Here are simple definitions of terms that you should know if you are concerned with RF or EMF hazards and where they might originate, or how they might be measured

Electrical power transformer on a utility pole in the U.S. (C) Daniel Friedman

Here we provide a summary of EMF, EMR, and radio frequency cycle rates, and where they are used. Our definitions are arranged in order of increasing frequency or decreasing wave length of electromagnetic signals.

So a typical low cost instrument suitable to measure power line EMF or Hz is not suitable for TV transmissions measurement in the
MHz range.

Definitions of Electromagnetic Frequencies, EMF, EMR, SAR, RF, Radio Waves, Microwaves

Definitions of Electromagnetic Radiation Terms

Cell antennas (C) Daniel Friedman

Our photo shows a collection of several types of radio transmit/receive antennas in Buenos Aires, Argentina.

Definition of EMF - an EMF or electromagnetic field is the field or area of force caused by movement of an electrical charge and containing some amount of electromagnetic energy.

Definition of EMR - Electromagnetic radiation, or electromagnetic radio frequency radiation EMFR. EMR or electromagnetic radiation is electrical and magnetic energy emitted by various types of energy sources: radio waves, microwaves, light, x-rays, and nuclear energy and sometimes expressed or measured in photons (particles) or as waves (discussed here).

EMR or EM radiation is the result of oscillating electrical and magnetic fields that move as an energy force in wave form through space.

Depending on the wavelength of a particular EMR source, it may be visible to the human eye (in the light spectrum).

While we provide more detailed definitions of types of EMR in this article, roughly EMR is divided according to its wavelength (in order of decreasing wavelength) into electrical energy (such as 60 cycle electrical current in a home, electrons oscillating in an electrical wire), radio waves, microwaves, visible light, ultraviolet light, x-rays, and gamma rays.

The higher the frequency of EMR the shorter is its wavelength. In general, electromagnetic radiation (EMR) is synonymous with electromagnetic waves.

Depending on wavelength, energy level, exposure, distance, and other factors, the biological effects of EMR may be heating (warming a chicken leg in a microwave oven), or ionization (knocking an electron off of a molecule to create an ion), to possibly profound effects on molecules or on cells of living tissue.

Power substation Pleasant Valley NY (C) Daniel Friedman

Definition of Ionizing radiation - ionizing radiation is electromagnetic waves powerful enough to change (ionize) molecules of a substance (human tissue, for example) that they strike.

Ionizing means creating an "ion" form of a molecule - that is, detaching an electron, converting the molecule to an "ionized" form with a different electrical charge. Ionizing radiation is known to be dangerous to humans and other animals.

It is the energy level of an electromagnetic wave that causes it to become ionizing, not the number of waves that occur. Short-wavelength (high frequency UV [ultra violet], X-rays, gamma rays) radiation is ionizing while low-frequency radiation is not.

Examples of ionizing radiation include high frequency radiation such as from X-rays, gamma rays, or nuclear radiation, alpha rays, beta rays, and neutrons from a nuclear reaction.

Definition of Non-ionizing radiation - low power non-ionizing radio waves at low levels of transmission power, such as older analog cell phone signals and cell phone radiation.

Definition of SAR & SAR Limits - Specific Absorption Rate of Radiation - measures the amount of radiation that a human body absorbs from a source such as from a nearby radio transmitting antenna or cellphone (radio receiving antennas do not emit EMF). In the United States the FCC requires that the SAR for cell phones is required to be no more than 1.6 watts per kilogram.

Table of Electromagnetic Radiation Frequencies

The following table summarizes the radiation frequency (cycles per second or Hertz or Hz) and wavelengths (physical length of waves) for various types of electromagnetic radiation sources such as radio waves, microwaves, light, and x-rays. The EM range or EM frequencies extend from a low end of about 1 kHz to 2.4×1023 Hz. - Wikipedia 6/10.

Summary Table of Frequencies of Electromagnetic Radiation

Type of Electromagnetic Radiation Source

Arranged in order of increasing frequency (decreasing wavelength)

Wavelength in Meters

Arranged in order of decreasing wavelength. Wavelength is defined here as the distance covered by one cycle of a wave.

Electromagnetic Frequency (Hertz1)

Arranged in order of increasing frequency .

Frequency is defined here as the number of waves per second passing a given point or location.

EMF/ULF: electromagnetic field source from typical residential electrical power

Household electrical current, home wiring, electric meters, service entry cables.

Power Transmission lines

Note that power transmission lines and home 120V or 240V appliances operating on 60 cycle alternating current are working at a frequency included in th3e ULF range described just below.

50 Hz or 60 Hz alternating electrical current

To measure in this range see

and also see


Ultra Low Frequency Radiation

Used in mining communications below ground, seismic monitoring, secure military communications via ground transmission

These are the longest electromagnetic waves, geomagnetic pulsations, micropulsations. Wavelength may be 5000 x radius of the earth

1 Hz up to 1kHz

Most sources: under 300 Hz

Other sources:
0.01 to 3 Hz
1 Hz to below 300 Hz
period of 100 seconds


Very Low Frequency Radiation VLF

Used for radio navigation, submarine communication, geophysical surveys, some natural emissions

10,000 meter band,

Myriameter wave

2 kHz up to 30 kHz

Other sources:
3 kHz up to 30 kHz

Myriameter band

Low Frequency Radiation - range of human hearing  Frequency range of human hearing, in sound pressure variations per second

12 Hz up to 20 kHz or about 15 to 20,000 cycles. [4] That is, from about 12 cycles per second up to 20,000 cycles per second.

Some sources place the human auditory threshold at 3 cycles/sec.

Low Frequency Radiation

Used for aircraft navigation, LORAN, weather, time signals

1,000 meter band,

Kilometer wave

30 kHz up to 300 kHz

AM broadcasting in Europe & other areas

Longwave band, kilometer band

Medium Frequency MF 
AM Radio Waves

AM and other Radio broadcasting, electrons oscillating in an antenna.

103 down to 10-1

100 meter band, Hectometer wave


300 kHz up to 3 MHz - 106 up to 109

530 kHz to 1600 kHz AM radio Broadcast band
Hectometer band

High Frequency HF 
AM Radio Waves

AM Radio broadcasting, electrons oscillating in an antenna.

100 meters down to one meter - 103 down to 10-1 (one meter)

10 meter band, Decameter wave

3 MHz up to 30 MHz

Decameter band

To measure in this range see

Very High Frequency VHF
 FM Radio & TV Waves

FM Radio and TV broadcasting, electrons oscillating in an antenna.

1 meter band 30 MHz up to 300 MHz -

Ultra High Frequency UHF
FM & TV Radio Waves
Mobile phones - cell phones, 3-G wireless, satellite communications

Radio and TV broadcasting,
Cell phones, Cell towers, (RF or "radiofrequency" waves, or loosely, "microwaves")
Satellite communications;
Electrons oscillating in an antenna.
* The current US exposure standard for cell site radiation in the US is 580-1000 microwatts per square centimetre.

1 meter down to 10 cm

300 MHz up to 3 GHz -


Cordless phones - roughly 100-900 MHz
Cell phones - GSM 380- 1990 MHz
Cell phones - TACS 900 MHz (Europe)
Cell phones - other designs: 450MHz

Radar - marine, low end units operate at 3 GHz
Typical 4-band cell phone: 850/900./1800/1900 MHz

To measure in this range see

Extremely High Frequency EHF

Molecular rotation, plasma oscillation

10-1 down to 10-4 meters

30-300 Gigahertz GHz - 109 up to 1012

Marine Radar operates typically from about 2 GHz up to 10 GHz

To measure in this range see


Molecular rotation, plasma oscillation

10-4 down to 0.7 ×10-6 Terahertz THz - 1012 up to 1015

Visible light

Molecular electron excitation - interaction with human eye retinal cells

0.7 ×10-6 down to 0.4 ×10-6 1015

Ultraviolet light

Molecular & atomic electron excitation

0.4 ×10-6 down to 10-8 1015 up to 1017


Excitation & ejection of core atomic electrons

10-8 down to 10-12 1017 up to 1021

Notes to the table:

  1. See our table comparing different Hertz frequency ranges at Hertz - Definitions of KHz MHz GHz THz
  2. How do we get to "approximately the speed of light" for data in the electromagnetic radiation wavelengths and frequencies above? For a given electromagnetic wave, multiplying the wavelength by wave frequency for any given electromagnetic signal will equal to roughly the speed of light.
  3. Definitions: One Hz or Herz = one cycle per second or one "wave" per second passing a given point
    One kHz or Kilohertz = one thousand cycles per second or 1000 waves per second
    One MHz or Megahertz = one million waves or cycles per second
    One GHZ or Gigahertz = one billion waves or cycles per second passing a given point
  4. Range of human hearing, citations:
    • Cutnell, John D. and Kenneth W. Johnson. Physics. 4th ed. New York: Wiley, 1998: 466.
    • "Body, Human." The New Book of Knowledge. New York: Grolier, 1967: 285.
    • Caldarelli, David D. and Ruth S. Campanella. Ear. World Book Online Americas Edition. 26 May 2003.

Cellphone Radiation Information & Reducing Cellphone EMR Exposure

Please see our full article on this topic found at Cell phone Radiation Hazards.

Excerpts from that article are below

Readers of this article should also see EMF RF FIELD & FREQUENCY DEFINITIONS


Definition of cellphone radiation - cellular telephones, because they include a radio transmitter, emit electromagnetic fields (EMF, or EMR).

In the United States the Federal Communications Commission (FCC) specifies the allowable limits of cell phone radiation. A possible concern is the exposure of the human ear and brain to cellphone radiation, especially as newer digital cell phones operate at higher power and at frequencies in the 1800-2000 MHz range.

Present cell phones may exceed the FCC EMR limit that was set when most cell phones were analog in signal design and emitted lower-strength EMFs in the 800-900 MHz range.

Scientific research on possible health hazards from cellphone use to date (2010) has produced inconclusive and conflicting results, varying by study. According to an article in June 2010 the New York Times,

Both the National Cancer Institute and the F.C.C. [Federal Communications Commission] say that there is no scientific evidence that wireless phones are dangerous, but each agency continues to monitor continuing medical studies.

What type of radiation is emitted by a cellphone? older cell phones emit and receive low level radio frequency waves from 200 MHz to more than 800 MHz. Newer cell phones operate in the 900 MHz to 2.4 GHz or more (approaching the power and frequency of microwaves and infrared waves).

Transmission of signals in the cellphone range are also referred to as UHF or Ultra High Frequency Signals.

Base to Mobile and Mobile to Base Cellphone Frequencies May Differ

It is worth noting that typically the signals that pass between a cell phone and a cell tower are at different frequency ranges depending on the direction of transmission.

For example, a cell phone may transmit from the phone to the cell tower at around 800 MHz, while the tower transmits back to the cellphone at around 1800 MHz.

Because the power level of a cellphone while it is transmitting is very small compared to the powe of the cell phone tower when it is transmitting, that means that the stronger of the two cell phone frequencies is the tower transmission signal.

In reading various publications that discuss cell phone frequencies, you may read the cellphone transmit frequency as "mobile to base" and the tower transmit frequency from tower to cellphone as "base to mobile".

Cellphone Abbreviations and Terms - What Frequencies Your Cellphone Uses Depend on Your Wireless Carrier as Well as the Phone Itself

AMPS - Advanced Mobile Phone Service - Cell phone industry standard since 1978

Analog service: radio signals modulated to carry information in a continuous signal, like FM radio. Receiver and transmitter use the same frequency.

Digital cell phone service: radio signals are digitized using a binary code (0's and 1's) to convert speech (or any signal sent to or received from a cellphone) to binary data. In the U.S there are 3 wireless technologies: CDMA, TDMA, and GSM.

- 800 MHz band authorized by the U.S. FCC in 1987 for cellphone use.

PCS - Personal Communications Services - 1.9 GHz all digital transmission and reception authorized by the U.S. FCC

SIM cards - Subscriber Identity Module cards are small printed circuit boards that contain individual cell phone account information and that are inserted into GSM phones (in the U.S.).

Because the SIM card contains the user information, cellphones that accept SIM cards become generic - you can move your cell phone account to a new telephone by inserting your SIM card into a new phone, or you can change your cell phone to a different service provider (and telephone number) by buying and inserting a different SIM card into your existing GSM phone.


Continue reading at DEFINITIONS of HERTZ, KHz MHz GHz THz or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CELL PHONE RADIATION - our full article on this topic

Or see these

Articles About Electromagnetic Fields, Hazards, Measurements

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DEFINITIONS of EMF RF FIELD & FREQUENCY at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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