100 ' ********************************

110 ' *  IBM PC BASIC VRESION A3.30  *

120 ' *  FILE NAME "FADING"          *

130 ' *  LINE-OF-SIGHT  FADING       *

140 ' *  1987/10           I.KATO    *

150 ' ********************************

160 KEY OFF:CLS:SCREEN 0

170 COLOR 14

230 LOCATE 1,1:PRINT "[ITEM 16]           FADING IN LINE-OF-SIGHT TRANSMISSION "    :PRINT:COLOR 7

240 PRINT "Span loss has been so far calculated on the assumption that meteorological      status is stable over the whole propagation path. In an actual path, however,"

250 PRINT "the climate changes every moment, and span loss varies accordingly."

260 PRINT "This phenomenon is called fading.":PRINT

270 PRINT "In a line-of-sight path, fading is caused by two factors, that is, the formationof a radio duct and the variation of k.":PRINT

280 PRINT "For a radio relay system to transmit multiplexed telephone messages or video    signals stringent conditions should be imposed on the thermal noise generated byfading over all repeater sections.  The CCIR recommends definite objectives for"

290 PRINT "the hypothetical reference circuit of 2500km in length, based on variations of  fading conditions.":PRINT

300 PRINT "Accordingly, the received power in each repeater section should be modified to  contain sufficient fading margin from its free space value discussed in Item 2.":COLOR 3

310 PRINT "        PR-M>=TH (dBm)":COLOR 7

320 PRINT "        Where PR is received power in  dBm,"

330 PRINT "              M  is fading margin (about 30dB),"

340 PRINT "              TH is receiver threshold level in dBm."

350 COLOR 6:LOCATE 23,20:PRINT "  -----menu:   Hit space key  -----"

360 COLOR 7:Q$=INKEY$:IF Q$<>" " THEN 360

370 CLS:SCREEN 0:RUN "ME"