A Brief Look at the Electromagnetic Spectrum
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A Brief Look at the Electromagnetic Spectrum
Relationship Between Wavelength and Frequency
Speed of light: 299,792,458 meters/second (exact by definition)
186,282 mile/s
(Speed of light) = (Wavelength) x (Frequency)
c = ln
Acronyms used in the Band Designations
ELF: 3-30 Hz, (Extremely Low Frequency)
SLF: 30-300 Hz (Super Low Frequency)
ULF: 300Hz-3KHz (Ultra Low Frequency)
VLF: 3-30 KHz (Very Low Frequency)
LF: 30-300 KHz (Low Frequency)
MF: 300KHz – 3MHz (Medium Frequency)
HF: 3-30 MHz (High Frequency)
VHF: 30–300 MHz (Very High Frequency)
UHF: 300 MHz – 3 GHz (Ultra High Frequency)
SHF: 3-30 GHz (Super High Frequency)
EHF: 30-300 GHz (Extremely High Frequency)
IHF: 300-3000 GHz (Insanely High Frequency) (just kidding)
Standard time and frequency stations
JJY in Japan (40 kHz and 60 kHz)
MSF in Rugby, England (60 kHz, 5 km, 3.1 miles)
WWVB in Colorado, USA (60 kHz)
HBG in Prangins, Switzerland (75 kHz)
DCF77 near Frankfurt am Main, Germany (77.5 kHz)
LORAN (LOng RAnge Navigation)
is a terrestrial navigation system using low
frequency radio transmitters that use the time interval between radio signals received from
three or more stations to determine the position of a ship or aircraft. The current version of
LORAN in common use is LORAN-C, which operates in the low frequency 90 to 110 kHz band.
LORAN is being widely displaced by GPS.
Radio
AM radio: 535 KHz to 1.7 MHz
( 1 MHz  300 m ~ 328 yards)
Short wave radio: Bands from 5.9 MHz to 26.1 MHz
Citizens band (CB) radio: 26.96 - 27.41 MHz
FM radio: 88 - 108 megahertz
( 98 MHz  10 ft)
Miscellaneous Consumer Electronics
Garage door openers: 40 MHz
Older Cordless phones: 40-50 MHz, 900 MHz
Baby monitors: 49 MHz
Radio controlled cars and airplanes: 72-75 MHz
Wildlife tracking collars: 215-220 MHz
Personal Computer: ~ 3 GHz
Primary Amatuer Radio Bands
Amateur radio, or Ham radio, is a hobby enjoyed by about 3 million people throughout the world.
Common Ham bands.
Photo shows a “ham
shack” in Kansas.
Broadcast Television
Television: Broadcast channels 3-83 have frequencies in the range from 45-885 MHz. Satellite TV is
currently broadcast in the 12.2-12.7 GHz band in the US and the 10.7-12.75 GHz band in Europe.
Channels 1-6: 45-83 MHz
Channels 7-13: 175-211 MHz
Channels 14-83: 471-885 MHz
The Panasonic 103 inch plasma
television has it's Canadian unveiling
in Toronto on Wednesday Dec. 6,
2006. The television is the world's
largest plasma device, weighing in at
nearly 600 pounds and costing
$80,000 CDN (about $69,000 US).
TV Sattelite Bands
Cell Phones
Regardless of the terminology (Modes) used to characterize cellular
technology (PCS, TDMA, CDMA, GSM, GPRS, Cellular, Digital, Analog, etc.),
at this time there are only two frequency ranges available to US carriers.
(1) 824 - 896 MHz
(2) 1.85 -1.99 GHz
Hands free set
Air Traffic Control Radar: 0.96-1.215 GHz
Global Positioning System (GPS): 1.227-1.575 GHz
WiFi: 2.4 GHz for 802.11b and 802.11g.
5 GHz for 802.11a
WiFi is a brand name. The underlying technology is known as Wireless Local Area Network (WLAN)
Microwave oven: 2.45 GHz
Bluetooth – Bluetooth is essentially a cable replacement technology, allowing electronic devices
such as cell phones, modems and printers to talk to each other wirelessly. It operates in the licensefree ISM band at 2.45 GHz. The band is divided into 79 channels, each 1 MHz wide. Channels are
changed up to 1600 times per second.
Where does the Bluetooth name come from? It is named after a Danish Viking and King,
Harald Blåtand (translated as Bluetooth in English), who lived in the latter part of the 10th century.
Harald Blåtand united and controlled Denmark and Norway (hence the inspiration on the name:
uniting devices through Bluetooth). He got his name from his very dark hair which was unusual for
Vikings, Blåtand means dark complexion. Alternatively, he was thought to like blueberries.
Traffic Radar Bands
Jammer
Microwave and mm-Wave
Band Designations
Radio Astronomy
Most radio astronomy observations are made in the band from about 30 GHz to 1 THz, but
there are instruments planned for observations beyond 1 THz.
The Green Bank Telescope (GBT),
aka the Great Big Telescope. It is
the world’s largest fully steerable
radio telescope.
Radio Astronomy Band
Atmospheric Absorption
Infrared (IR): from the Latin infra, "below“. The infrared is the region
of the spectrum just below the visible red.
IR technologies include:
Military target acquisition and tracking
Night vision
Remote temperature sensing
Short-ranged wireless communication
(remote controls for TV, stereo, etc,)
Spectroscopy
Weather forecasting
Infrared astronomy
At the atomic level, infrared energy elicits vibrational modes in molecules through a change
in the dipole moment, making it a useful frequency range for study of these energy states.
Far Infrared (FIR): The far infrared is the lower frequency portion of
the IR band.
Far-infrared waves are thermal. FIR light
penetrates beyond the skin level and is
absorbed efficiently by cells below, whereas
visible light is mostly bounced off the skin
surface. Far-infrared can penetrate up to 11/2 inches, exciting the vibrational energy of
molecules and resonating with cells. FIR rays
can thus raise the core body temperature.
Near infrared waves are not perceived as
hot. These shorter wavelengths are the ones
used by your TV's remote control.
There is an entire industry of health products designed to operate in the FIR.
The human eye detects electromagnetic radiation in the visible spectrum.
Visible technologies include:
Lenses
Mirrors
Polarizers
Beam splitters
Prisms
Diffraction gratings
Photodetectors
Lasers
Fiber optic cable
Light bulbs
LEDs
The near ultraviolet is absorbed very strongly in
the surface layer of the skin by electron
transitions. As you go to higher energies, the
ionization energies for many molecules are
reached and the more dangerous photoionization
processes take place. Sunburn is primarily an
effect of uv, and ionization produces the risk of
skin cancer.
The ozone layer in the upper atmosphere is
important for human health because it absorbs
most of the harmful ultraviolet radiation from the
sun before it reaches the surface. The higher
frequencies in the ultraviolet are ionizing
radiation and can produce harmful physiological
effects ranging from sunburn to skin cancer.
Health concerns for UV exposure are mostly for
the range 290-330 nm in wavelength, the range
called UVB. According to Scotto, et al, the most
effective biological wavelength for producing skin
burns is 297 nm. Their research indicates that
the biological effects increase logarithmically
within the UVB range, with 330 nm being only
0.1% as effective as 297 nm for biological
effects. So it is clearly important to control
exposure to UVB.
X-Ray – Electromagnetic radiation of extremely short wavelength and high frequency.
Wavelengths: 10-8 to 10-11 m (10-0.01 nm)
Frequency: 3x1016 to 3x1019 Hz (30-30,000 PHz)
Gamma Rays are high energy waves/particles that can penetrate deeply into solid objects.
Their energy is sufficient to cause damage to living cells.
Frequency: (1018 – 1021) Hz
Gamma-rays are generated by;
Supernova explosions
Destruction of atoms
Nuclear explosions
Decay of radioactive material
Neutron stars
Pulsars
Black holes
Image of entire sky in 100 MeV or greater gamma rays as seen by the EGRET instrument aboard the
CGRO spacecraft. Bright spots within the galactic plane are pulsars while those above and below the
plane are thought to be quasars.