निम्न आवृत्ति (LF)

मुक्त ज्ञानकोश विकिपीडिया से
यहाँ जाएँ: भ्रमण, खोज


निम्न आवृत्ति (LF)
साइकिल प्रति सै: 30 kHz to 300 kHz

तरंगदैर्घ्य: 10 km to 1 km

निम्न आवृत्ति या LF वे रेडियो आवृत्ति होती हैं, जो कि 30 kHz–300 kHz के मध्य आती हैं । इसे किलोमीटर पट्टी या तरंग भी कहते हैं । क्योंकि इसका तरंग दैर्घ्य दस से एक किलोमीटर होता है ।

सामरिक प्रयोग[संपादित करें]

प्रयोग एवं अमेच्योर[संपादित करें]

A 2.1 kHz allocation, the 136 kHz band (135.7 kHz to 137.8 kHz), is available to amateur radio operators in some countries in Europe, New Zealand and French overseas dependencies. The world record distance for a two-way contact is over 10,000 km from near Vladivostok to New Zealand.[1] As well as conventional Morse code many operators use very slow computer controlled Morse code or specialized digital communications modes. A proposal at the WRC-07 World Radiocommunication Conference aims to make this a worldwide amateur radio allocation.

The UK allocated a 2.8 kHz sliver of spectrum from 71.6 kHz to 74.4 kHz beginning in April 1996 to UK amateurs who applied for a Notice of Variation to use the band on a noninterference basis with a maximum output power of 1 W ERP (effective radiated power). This was withdrawn on 30 June 2003 after a number of extensions in favor of the European-harmonized 136 kHz band.[2] A 1-watt transmission of very slow Morse Code between G3AQC (in the UK) and W1TAG (in the USA) spanned the Atlantic Ocean for 3275 miles on November 21-22, 2001.

In the United States there is a special license free allocation in the longwave range called LowFER. This experimental allocation between 160 kHz and 190 kHz is sometimes called the "Lost Band". Unlicensed operation by the public is permitted south of 60 degrees north latitude, except where interference would occur to ten licensed location service stations located along the coasts. Regulations for use include a power output of no more than 1 watt, and an antenna/ground-lead length of no more than 15 meters, and a field strength of no more than 4.9 microvolts/meter. Also, emissions outside of the 160 kHz–190 kHz band must be attenuated by at least 20 dB below the level of the unmodulated carrier. Many experimenters in this band are amateur radio operators.

मौसम संबंधी प्रसारण[संपादित करें]

A regular service transmitting RTTY marine meteorological information on LF is the German Meteorological Service (Deutscher Wetterdienst or DWD). The DWD operates station DDH47 on 147.3 kHz using standard ITA-2 alphabet with a transmission speed of 50 baud and FSK modulation with 85 Hz shift[3].

रेडियो नौवहन संकेत[संपादित करें]

रेडियो प्रसारण[संपादित करें]

यह प्रसारण होता है 148.5 से 283.5 kHz के मध्य, यूरोप एवं एशिया के भागों में ।

एण्टीना[संपादित करें]

रेडियो वर्णक्रम
अत्यधिक निम्न आवृत्ति (ELF) परम निम्न आवृत्ति (SLF) अत्यन्त निम्न आवृत्ति (ULF) अति निम्न आवृत्ति (VLF) निम्न आवृत्ति (LF) मध्यम आवृत्ति (MF) उच्चावृत्ति (HF) अत्योच्चावृत्ति (VHF) अत्यन्त उच्चावृत्ति (UHF) परम उच्चावृत्ति (SHF) अत्यधिक उच्चावृत्ति (EHF)
3 Hz 30 Hz 300 Hz 3 किलो हर्ट्ज़ 30 किलो हर्ट्ज़ 300 किलो हर्ट्ज़ 3 मैगा हर्ट्ज़ 30 मैगा हर्ट्ज़ 300 मैगा हर्ट्ज़ 3 गीगा हर्ट्ज़ 30 गीगा हर्ट्ज़
30 Hz 300 Hz 3 किलो हर्ट्ज़ 30 किलो हर्ट्ज़ 300 किलो हर्ट्ज़ 3 मैगा हर्ट्ज़ 30 मैगा हर्ट्ज़ 300 मैगा हर्ट्ज़ 3 गीगा हर्ट्ज़ 30 गीगा हर्ट्ज़ 300 गीगा हर्ट्ज़


  1. "QSO ZL/UA0 on 136 kHz". The World of LF. http://www.wireless.org.uk/newspic92.htm. 
  2. "UK Spectrum Strategy 2002". Ofcom. http://www.ofcom.org.uk/static/archive/ra/topics/spectrum-strat/future/strat02/strategy02app_a.doc. 
  3. "DWD Sendeplan". http://www.dwd.de/de/wir/Geschaeftsfelder/Seeschifffahrt/Sendeplaene/Sendeplaene.htm. अभिगमन तिथि: 2008-01-08.