Electromagnetic spectrum




Electromagnetic radiation class Frequency Wavelength Energy
Ionizing radiation γ   300 EHz 1 pm 1.24 MeV
  Gamma rays      
    30 EHz 10 pm 124 keV
X X-rays      
HX Hard X-rays(100-200pm) 3 EHz 100 pm 12.4 keV
SX   300 PHz 1 nm 1.24 keV
  Soft X-rays      
    30 PHz 10 nm 124 eV
EUV Extreme ultraviolet       
      3 PHz 100 nm 12.4 eV
  NUV Near ultraviolet      
      300 THz 1 μm 1.24 eV
  NIR Near infrared      
      30 THz 10 μm 124 meV
  MIR Mid infrared      
Radiowaves     3 THz 100 μm 12.4 meV
  FIR Far infrared      
      300 GHz 1 mm 1.24 meV
  EHF Extremely high frequency    
      30 GHz 1 cm 124 μeV
Microwaves SHF Super high frequency      
      3 GHz 1 dm 12.4 μeV
  UHF Ultra high frequency      
      300 MHz 1 m 1.24 μeV
  VHF Very high frequency      
      30 MHz 10 m 124 neV
  HF High frequency      
      3 MHz 100 m 12.4 neV
  MF Medium frequency      
      300 KHz 1 Km 1.24 neV
  LF Low frequency      
      30 KHz 10 Km 124 peV
  VLF Very low frequency      
      3 KHz 100 Km 12.4 peV
  ULF Ultra low frequency      
      300 Hz 1 Mm 1.24 peV
  SLF Super low frequency      
      30 Hz 10 Mm 124 feV
  ELF Extremely low frequency      
      3 Hz 100 Mm 12.4 feV



Note: Electromagnetic waves with a wavelength of 1 to 10 millimetres (1 cm), are called millimeter waves (millimetre band), abbreviated MMW or mmW 







Notes on the power of electromagnetic radiation


Excerpt from link: http://www.strixsystems.com/cshealthconcernsaboutwifi.aspx


"Whereas most cell phones have a peak power output of 2 Watts (some at 3), most Wi-Fi routers have a peak power output of less than 100mW which is typical of indoor access points, and 400 or 500mW for outdoor units, but unlike cell phones and their base stations, Wi-Fi devices do not communicate continuously.   Dr. Kenneth Foster, a professor of bioengineering at the University of Pennsylvania, recently completed a study of Wi-Fi, taking over 350 measurements at 55 sites across four countries.  According to his research, not only does Wi-Fi equipment emit less radiation under load, it does so in much smaller bursts.  “When the networks were not being used, the duty cycle was 0.01 percent or so. That means that it is radiating power for 0.01 percent of the time.”   While Wi-Fi and microwaves use the same 2.4 GHz frequency, a microwave oven sends much more intense emissions than a Wi-Fi deviceor cell phone."


Allocation of Radio Spectrum in the United States




(link shared by Robert Duncan)


Worldwide Spectrum Allocations Courtesy of Tektronix






Signal Identification Guide




FCC frequency explorer




France - Tableau national de répartition des bandes de fréquences (Agence Nationale de Fréquences) 







"Celebrating Paulin Morrow Austin, a founder of RADAR Meterorology"

(MIT School of Science post)
Excerpt: "After completing her thesis work on the “Propagation of electromagnetic pulses in the ionosphere,” and with Stratton’s encouragement, Austin joined MIT’s Weather Radar Research Project at its inception in 1946. This was the first critical investigation into how radar technology could be used to monitor weather; she focused on comparing measurements of actual rainfall with those found using radar. “She really had a love affair of measuring rainfall with radar and doing it quantitatively, and she did that for decades.(...)
“The reason that the whole United States is covered with s-band radar, it’s probably safe to say, [is] because of Polly Austin. In Europe, there are many networks of c-band radars, but Polly knew that if you wanted accurate [rain] measurements, you had to go with s-band,” said Williams. Austin was also instrumental in installing radomes on MIT's Green Building (Building 54), home of EAPS.
Austin also chaired the American Meteorological Society’s Committee on Radar Meteorology, and in 1974, she was the first woman to be elected a councilor."


Software based radio


On process of certification by the FCC to be able to market software-defined radio in the US. 


Link from IEEE 
http://spectrum.ieee.org/geek-life/hands-on/a-40-softwaredefined-radio says "Which brings us to regulatory issues. In some countries, it’s illegal to receive any frequency you don’t have a license for, apart from public broadcast frequencies. In the United States, you’re free to pick up nearly all the signals you can receive. There are, however, important exceptions to this general rule, such as a ban on listening to cellphone frequencies, or operating equipment capable of picking up police signals while you’re in a vehicle (the latter is permitted with a ham license)."


Comment from http://hackaday.com/2015/02/12/why-you-should-care-about-software-defined-radio/
RTL-SDR can pick up any signal that would be receivable at your location anywhere between 24 MHz and 1700 MHz if you have the most common type of RTL-SDR (RTL2832 + R820T chipset) and a good antenna. With software such as SDR# (my personal favorite), you can take a good look any of those signals. Will it DECODE cell signals? Definitely not. Also, doing so in the US is technically illegal. Things may be different if you live in another country, so check your local laws.



Indicative dongle and software
https://www.amazon.fr/NooElec-NESDR-Mini-T%C3%A9l%C3%A9commande-antistatique/dp/B00VZ1AWQA/ref=sr_1_fkmr0_2?s=electronics&ie=UTF8&qid=1487243127&sr=1-2-fkmr0&keywords=puce+R820T2 et ce logiciel https://play.google.com/store/apps/details?id=marto.androsdr2. Merci d'avance. 








Electromagnetic Spectrum Analysis


Radiofrequency Sweep or Scanning



"Radio frequency sweep or "Frequency sweep" or "RF sweep" refer to scanning a radio frequency band for detecting signals being transmitted there. This is implemented using a radio receiver having a tunable receiving frequency. As the frequency of the receiver is changed to scan (sweep) a desired frequency band, a display indicates the power of the signals received at each frequency."



Video demonstrating sweep of the FM band





Analyse du spectre électromagnétique 


Analyse par balayage (scanning) fréquentiel (pour exploration spectrale)

Il faut noter que la vitesse de balayage influence la résolution spectrale.


Analyseur de champ électromagnétique


Un analyseur de champ électromagnétique est un instrument de mesure regroupant deux capteurs :