OZ NR. 4 . APRIL 1963. 35. ÅRGANG, edr.dk: Antenner - på en anden måde. Af OZ7AQArkiveret 14. oktober 2018 hos Wayback Machine: Citat: "...Vor sendeantenne er nemlig omgivet af to forskellige elektromagnetiske felter, nærfeltet og fjernfeltet. Fjernfeltet skyldes den fra antennen udstrålede energi, der — når den een gang har forladt antennen — fortsætter upåvirket af, hvad vi derefter foretager os, og aldrig vender tilbage. Nærfeltet benævnes også induktionsfeltet, og er den virkning af strømmen, vi er fortrolig med i elektromagneter, transformere og svingningskredse. Det er nærfeltet, vi kan påvise med en glimlampe eller en lille gløde lampe tilsluttet en ring af kobbertråd. Sådan en indikator vil vise, at feltet aftager meget hurtigt, når vi fjerner den fra antennen, lige som det er tilfældet, når vi fjerner den fra PA-spolen i senderen..."
ncsu.edu
news.ncsu.edu
July 27, 2011, news.ncsu.edu: What Do Bees See? And How Do We Know?, backup Citat: "...Humans see light in wavelengths from approximately 390 to 750 nanometers (nm). These wavelengths represent the spectrum of colors we can see. Bees, like many insects, see from approximately 300 to 650 nm. That means they can’t see the color red, but they can see in the ultraviolet spectrum (which humans cannot). Bees can also easily distinguish between dark and light – making them very good at seeing edges..."
OZ NR. 4 . APRIL 1963. 35. ÅRGANG, edr.dk: Antenner - på en anden måde. Af OZ7AQArkiveret 14. oktober 2018 hos Wayback Machine: Citat: "...Vor sendeantenne er nemlig omgivet af to forskellige elektromagnetiske felter, nærfeltet og fjernfeltet. Fjernfeltet skyldes den fra antennen udstrålede energi, der — når den een gang har forladt antennen — fortsætter upåvirket af, hvad vi derefter foretager os, og aldrig vender tilbage. Nærfeltet benævnes også induktionsfeltet, og er den virkning af strømmen, vi er fortrolig med i elektromagneter, transformere og svingningskredse. Det er nærfeltet, vi kan påvise med en glimlampe eller en lille gløde lampe tilsluttet en ring af kobbertråd. Sådan en indikator vil vise, at feltet aftager meget hurtigt, når vi fjerner den fra antennen, lige som det er tilfældet, når vi fjerner den fra PA-spolen i senderen..."
arrl.org: Why an Antenna Radiates Citat: "...And an accelerating or decelerating charged body, be it an electron or a pithball, is a source of electromagnetic radiation...The radiation field of an antenna transmits only real power, which travels out toward distant localities without ever reversing direction. [] The induction field carries only reactive power, [] and the coulomb field carries both real and reactive power..."
Jun 08, 2012, electronicdesign.com: What’s The Difference Between EM Near Field And Far Field? Citat: "...The far field is the real radio wave. It propagates through space at a speed of just about 300 million meters per second, which is the speed of light or nearly 186,400 miles per second. The E and H fields support and regenerate one another as their strength decreases inversely as the square of the distance (1/r^2). Maxwell described this phenomenon in his infamous equations..."
rfwireless-world.com: Near Field vs Far Field Antenna Radiation Pattern Citat: "...The region above the distance of 2 D^2/λ is referred as far field region. This region is also called as Fraunhofer region. In these region power radiated from antenna decays inverse of square of distance(1/R^2). Near field of the antenna will have more energy compare to the far field. This is because of proximity of EM wave to the antenna radiator part. Power in near field region follow 1/R^4 and hence power intensity falls off very rapidly..."
July 27, 2011, news.ncsu.edu: What Do Bees See? And How Do We Know?, backup Citat: "...Humans see light in wavelengths from approximately 390 to 750 nanometers (nm). These wavelengths represent the spectrum of colors we can see. Bees, like many insects, see from approximately 300 to 650 nm. That means they can’t see the color red, but they can see in the ultraviolet spectrum (which humans cannot). Bees can also easily distinguish between dark and light – making them very good at seeing edges..."
