10 REM calculated load capacitance for long wire antenna though the HF bands
   20 REM inductance to wire is 300nH / metre length
   30 REM 15metres of wire is half wavelenght at 10MHz, the wire has an inductance of 4.5uH equivalent coil
   40 REM reason : 1 metre of wire is equal to  300nH
   50 
   60 REM the Zo=SQR(RL^2 - XL^2) equation is the add on to the co-axial cable, the antenna end
   70 REM Thus so, with XL = 50, then the above equation then equals zero, and hence does add to the
   80 REM antenna with an antenna reactive loading.
   90 REM
  100 
  110 REM The value of reference in the Zo=SQR() equation is the cable impedance, as XL =50,
  120 REM the added load of the antenna to the cable equates to zero offset.
  130 
  140 REM By using the cable impedance, the wire is matched to the cable characteristic value.
  150 
  160 REM However if a 1/4 wavelength wire inductive resonance reactance value is used as RL, RL = 141ohms,
  170 REM then the wire is matched to the 1/4 wave length terminal impedance.
  180 
  190 REM for the 1/4 wave length match to be used, the ATU would have an input PI section Low Pass Filter, Fc = 30MHz
  200 REM the input of the LPF would be 50ohms to match the RF co-axial cable, but the LPF output would be 141ohms.
  210 
  220 
  230 REM   length_metres = the length of wire used for antenna, calculated into the equivalent inductance value
  240 
  250 length_metres = 50
  260 l = (length_metres*(300E-9))
  270 length_feet = ((100/2.54)*length_metres)/12
  280 
  290 REM the reactance_resonant_impedance is twice the cable impedance, or as required reactance_resonant_impedance for a matching stub, both used as the reference for RL
  300 reactance_resonant_impedance = 50
  310 
  320 PRINT " reactance resonant impedance = ";reactance_resonant_impedance;"ohms"
  330 PRINT " inductance of wire / coil = ";l*1E6;"uH inductance of a length of equivalent wire = ";INT(length_feet);"feet or ";length_metres;"metres"
  340 
  350 
  360 REM PRINT " length of equivalent wire = ";INT(length_feet);"feet or ";length_metres;"metres"
  370 
  380 PRINT
  390 
  400 FOR f = 0.1 TO 1 STEP 0.1
  410   
  420   REM inductive reactance
  430   XL= (2*PI*(f*1E6)*l)
  440   
  450   REM RL is low to reactance_resonant_impedance, thus the wire is capacitive and needs inductive loading
  460   IF XL <= reactance_resonant_impedance THEN PROC_low
  470   
  480   REM RL is high to reactance_resonant_impedance, thus thwe wire is inductive and needs capacitive loading
  490   IF XL > reactance_resonant_impedance THEN PROC_high
  500   
  510 NEXT f
  520 
  530 
  540 FOR f = 1 TO 30  STEP 1
  550   
  560   REM inductive reactance
  570   XL= (2*PI*(f*1E6)*l)
  580   
  590   REM RL is low to reactance_resonant_impedance, thus the wire is capacitive and needs inductive loading
  600   IF XL <= reactance_resonant_impedance THEN PROC_low
  610   
  620   REM RL is high to reactance_resonant_impedance, thus the wire is inductive and needs capacitive loading
  630   IF XL > reactance_resonant_impedance THEN PROC_high
  640   
  650 NEXT f
  660 END
  670 
  680 
  690 
  700 
  710 REM RL is low to reactance_resonant_impedance, thus the wire is short and capacitive thus needs inductive loading
  720 DEF PROC_low
  730 Xc_low = SQR(reactance_resonant_impedance^2 - XL^2)
  740 REM Xc_low used as XL, as opposite reactance required
  750 XLoad = Xc_low/((2*PI*(f*1E6)))
  760 PRINT TAB(1);" freq= ";f;"MHz";TAB(19);" XL=";XL;TAB(35);" Xload=";XLoad*1E6;"uH"
  770 ENDPROC
  780 
  790 
  800 REM RL is high to reactance_resonant_impedance, thus the wire is long and inductive thus needs capacitive loading
  810 DEF PROC_high
  820 XL_high = SQR(XL^2 - reactance_resonant_impedance^2)
  830 REM XL used as Xc, as opposite reactance required
  840 Xcload = 1/((2*PI*(f*1E6)*XL_high))
  850 PRINT TAB(1);" freq= ";f;"MHz";TAB(19);" XL=";XL;TAB(35);" Cload=";Xcload*1E12;"pF"
  860 ENDPROC