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  主页 : ITU-R; : 研究组; : : [SG 3 Databanks - LF/MF skywave Data Bank Explanatory Notes]
无线电通信部门(ITU-R)  
[SG 3 Databanks - LF/MF skywave Data Bank Explanatory Notes]

  • [1. All field strengths are expressed in dB relative to 1 microvolt per metre.]
  • [2. All field strengths are normalized to 300 mV/m at 1 km (i.e. power = 1 kW; antenna gain = 0 dB).]
  • [3. There are four separate files. The first file contains daytime field strengths] - [(Day).] - [The second file contains annual median field strengths measured at 6 hours after sunset in a year of solar minimum] - [(LFMFDATA),] - [see item 7 for exceptions). The third file contains field strengths measured in North America at different solar activity levels] - [(RANDMF).] - [The fourth file contains relative monthly field strengths (in dB) with respect to annual median values for the year and hour given] - [(SEASONAL).]
  • [4. In all files, Fm(p) denotes measured field strength exceeded for p% of the days (or, nights) of a year.]
  • [5. The first column of the LFMFDATA, the RANDMF and the SEASONAL files contain a 4-digit number. The first digit denotes the ITU Region in which the receiving site of that particular path is located. In the second digit, 1 denotes north and 2 denotes south. Users are urged not to delete this column. ]
  • [6. Column 2 of the above-mentioned files presents path names or codes used in the original documents when submitted to IWP 6/4.]
  • [7. Measurements presented in Path 2127 to 2130 (received at Churchill, CAN) and 2180 to 2182 (received at Strathburn, CAN) in LFMFDATA were taken in the time frame of 1947-1948, a period of relatively high solar activity. When performing calculated field strengths for these paths, Lr (loss of field strength due to solar activity) may be quite large and should not be neglected. ]

 

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