page_title: Non-directional beacon
section_title: Antenna and signal characteristics
hierarchical_section_title: Non-directional beacon / Antenna and signal characteristics
caption_attribution_description: Deutsch: Antenne für Flugnavigation, Ungerichtete Funkfeueranlagen (NDB), Frequenzbereich 255 - 526.5 kHz, diese Ferritantenne ist mit 16 kg Ferrit und einer Länge des Ferritstabes von 100 cm eine der grössten Ferritantennen der Welt. Hergestellt wurde diese NDB Antenne von BAZ Spezialantennen, Deutschland. English: Ferrite rod antenna for non-directional beacon (NDB), frequency 255 - 526.5 kHz, air navigation, with dimensions: length 100 cm, diameter of the ferrite 10 cm, weight 16 kg; one of the biggest ferrite antennas of the world. Русский: Ферритовая антенна используемой для аэронавигационных целей приводной радиостанции для диапазона частот 255 - 526.5 кГц, размеры антенны: длина 100 см, диаметр ферритового стержня 10 см, вес 16 кг; одна из самых больших ферритовых антенн в мире.
context_page_description: A non-directional beacon is a radio transmitter at a known location, used as an aviation or marine navigational aid. As the name implies, the signal transmitted does not include inherent directional information, in contrast to other navigational aids such as low frequency radio range, VHF omnidirectional range and TACAN. NDB signals follow the curvature of the Earth, so they can be received at much greater distances at lower altitudes, a major advantage over VOR. However, NDB signals are also affected more by atmospheric conditions, mountainous terrain, coastal refraction and electrical storms, particularly at long range.
context_section_description: NDBs typically operate in the frequency range from 190 kHz to 535 kHz (although they are allocated frequencies from 190 to 1750 kHz) and transmit a carrier modulated by either 400 or 1020 Hz. NDBs can also be collocated with a DME in a similar installation for the ILS as the outer marker, only in this case, they function as the inner marker. NDB owners are mostly governmental agencies and airport authorities.
  NDB radiators are vertically polarised. NDB antennas are usually too short for resonance at the frequency they operate – typically perhaps 20m length compared to a wavelength around 1000m. Therefore, they require a suitable matching network that may consist of an inductor and a capacitor to "tune" the antenna. Vertical NDB antennas may also have a 'top hat', which is an umbrella-like structure designed to add loading at the end and improve its radiating efficiency. Usually a ground plane or counterpoise is connected underneath the antenna.
caption: Ferrite antenna for non-directional beacon (NDB), frequency range 255–526.5 kHz
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