VOACAP Quick Guide: VOACAP & VOAAREA contours

VOACAP & VOAAREA contours
VOACAP Quick Guide: Home

There are three files, located in the default installation at C:\itshfbc\database\, where the contour values are defined for output parameters, to be used in VOACAP graphs & VOAAREA coverage maps:
VOACAP   GPH	VOACAP Point-to-Point parameter auto scaling info
VOAPLT   GPH	VOACAP auto scaling data used by AREAPLTW.EXE
Syntax
  xfact, icode, num, [ con(num) ]
Where:
  xfact = multiplying factor

          Usually either 1. or 100. (100 for percents)

  icode = calculating code

          0 = user-defined values given in CON (max of 6 allowed **)
          1 = MAX down in CON(1) increments, Min allowed CON(2)
          2 = MIN to MAX in 6 program-defined steps
          3 = MIN up in CON(1) increments, Max allowed CON(2)

  num   = number of numeric arguments to follow.

  con(num) = numeric arguments, up to num

          If num = 2, then two arguments have to follow. They become
          CON(1) and CON(2).

          When num = 0, there are no numeric arguments (icode = 2).

          The max value of num = 6 can only be used in the case of icode = 0.
** in reality, VOACAPW.EXE accepts 10 user-defined values. These need to be defined in the data input card.
Contour colors
The default values will be read from C:\itshfbc\database\colors.gph (for graphs) and C:\itshfbc\database\colors.con (for coverage maps). See http://www.uwasa.fi/~jpe/voacap/colors.html
Examples

1. USER DEFINED CONTOUR VALUES (ICODE = 0)
MUFday= % of days/month sky-wave propagation expected at MUF mode
        MUF days            expected            [%]
        100. 0  6 1. 10. 50. 90. 99. 110.
Explanations:

Multiply values in datafile by 100.
Use 6 values given.

2. PROGRAM DEFINED MAX TO USER DEFINED MIN + INCREMENT (ICODE = 1)
DBU   = Median field strength at receive location (dBu)
        Field Strength      Median              [dBu]
        1. 1  2 5. 0.
Explanations:

Find MAX in datafile (e.g. say it was 69)
Round up to the next multiple of CON(1) (70 in this case).
Contours start at 70 (but you will not see this one) and go down in steps of 5 [= CON(1)] for 6 contours. The lower limit will be 0 [= CON(2)]. Thus, if max was 14, contours would be >10, 5, <0.

3. PROGRAM DEFINED MAX, MIN AND INCREMENT (ICODE = 2)
TANGLE= Radiation angle (degrees)
        Radiation Angle     Transmit            [degrees]
        1. 2  0
Explanations:

Find MIN and MAX in datafile (e.g. 4.6, 32.3)
The steps are based on a complicated algorithm, but it essentially finds 6 contours within the min and max. In this case it would find <6,12,18,24,30,>30.
4. PROGRAM DEFINED MIN TO USER DEFINED MAX AND INCREMENT (ICODE = 3)
RPWRG = Required power & antenna gain to achieve reliab (dB)
        Required Power      & Antenna Gain      [dB]
        1. 3  2 10. 200.
Explanations:

Find MIN in datafile
Round down to the next multiple of CON(1)
Contours start at this value and go up in steps of 10 [= CON(1)] for 6 contours. The upper limit is 200 [= CON(2)].
icode=3 is opposite of icode=1, and is used for values that are really negative, but are calculated as positive values (such as LOSS & RPWRG).

Thank-you

This article would have not been possible without the help of Greg Hand who explained the syntax and provided the examples. Any errors in this article are therefore due to my own misinterpretation :)