Communication and direction finding princeple

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Communication and direction finding princeple

  1. 1. By Lt NS Wickramasinghe Bsc E & E Eng
  2. 2. There are two basic type of electronic communication COMMUNICATION Simplex Duplex One way communication information travels only one direction Two way communication information travel in two direction Ex : Radio and Television Ex : telephone
  3. 3. Electro Magnetic wave propagation in air can be divided in to Two WAVE PROPERGATION Longitudinal Transverse
  4. 4. There Are Two different ways which Electro Magnetic wave travel from a Transmitting antenna to a Receiving antenna RADIO WAVE Ground wave Sky wave
  5. 5. Ground wave is radio wave travel along the surface of the earth. They follows two distinct paths call Direct path and Reflected path
  6. 6. Sky wave often call Ionospheric waves radiated in upward direction and returned to earth at some distinct location due to refraction
  7. 7. Skip distance is the distance from the transmitter to the point ware the sky wave is first routed to the earth size of skip distance depend on Frequency , Incident angle and degree of ionisation
  8. 8. Amount of refraction in ionosphere depends on three factors Density of Layer Frequency of radio wave Angle at which wave enter to the Layer
  9. 9.  Troposphere- It has large variation humidity and temperature but has only small effect on electromagnetic wave at communication frequencies.  Stratosphere- This has stable temperature and humidity and has little effect on electromagnetic wave at communication frequencies.  Ionosphere – This sphere has reasonably stable temperature but contain Electron and Ionised gas and has major effect on propagation of MF and HF.
  10. 10. Ionosphere is the uppermost part of the atmosphere it is ionised by the solar power or the solar radiation. Ionosphere further classified to D,E and F. During the day time F layer split in to two as F1 and F2 The relationship between refraction index and free electron density is defines as Maxwell’s equation and it is as follows n = (1- 81N) f2 n- Refractive index N- Free electron density f- Frequency of the electromagnetic wave
  11. 11. As free electron density rise , refraction index falls. Hence refraction index varies with the F layer of Ionosphere
  12. 12. COMSETS SN TYPE 01 VHF 02 UHF 03 HF 04 DF(Rx) SEQUE H/H Motorola XTS 5000 Motorola XTS Motorola Astro 3000 Motorola Spectra Cougar Cougar B/S Motorola XTL 5000 Motorola XTL 5000 Motorola Astro Motorola Spectra Transwold RT 7000 Icom 718 (With H/H) NON SEQUE H/H Motorola GP Motorola Gm 338 300 Motorola Gm 300 ( X Motorola GP ) 328 FM Q 52 (X ) VX 150 VX 168 HYT 3600 P 020 GP 2000 B/S Motorola XTS 5000 RT 100 Chinees Transwold VR 5000 Icom 8500 DDF 6000 DDF6001
  13. 13. Listening and identifying radio frequencies transmitting by other parties. The DF systems using various techniques such as ; Adcock, Doppler, Quasi-Doppler and associated multiple-element, commutated (mechanical and electronic) arrays
  14. 14. ?

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