The FREQUENCY card in VOACAPX.DAT

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The VOACAPW.EXE is the calculation engine in the VOACAP that accepts the VOACAPX.DAT as input. This data input file is composed of a number of "control cards", or labeled lines.

There are a few things you can do with the FREQUENCY card (line) that are not available when using the VOACAP GUI for creating the data input file.

Below is the normal structure of VOACAPX.DAT (as created by the VOACAP GUI) when I want to know about the path from Vaasa (Finland) to New York (USA) on 7.05, 10.12 and 14.05 MHz:

COMMENT    Any VOACAP default cards may be placed in the file: VOACAP.DEF
LINEMAX      55       number of lines-per-page
COEFFS    CCIR
TIME          1   24    1    1
MONTH      2003 7.00
SUNSPOT     63.
LABEL     VAASA               NEW YORK
CIRCUIT   63.10N    21.60E    40.72N    74.00W  S     0
SYSTEM       1. 155. 3.00  90. 24.0 3.00 0.10
FPROB      1.00 1.00 1.00 0.00
ANTENNA       1    1    2   30     0.000[default\CCIR.000     ]  0.0    0.1000
ANTENNA       2    2    2   30     0.000[default\SWWHIP.VOA   ]  0.0    0.0000
FREQUENCY  7.0510.1214.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
METHOD       30    0
EXECUTE
QUIT

First of all, it is important to note that the placement of decimal points for frequencies on the FREQUENCY line is crucial since they are in fixed positions. You can mess the frequencies up big time if you are not careful. This is probably one of the reasons that there is an interface program that takes care of things like this.

Typically, the FREQUENCY line accepts up to 11 user defined frequencies. However, there are other ways of using the FREQUENCY line.

1. Calculating from 2 to 30 MHz

If you want to calculate the prediction for the whole HF range on the given path from 2.0 MHz to 30.0 MHz in 1.0 MHz steps, you write as follows:
FREQUENCY -1

The start of the result pages would be as follows:

      CCIR Coefficients        ~METHOD 30   VOACAP 03.0724W  PAGE   1

  Jul    2003          SSN =  63.                Minimum Angle= 3.000 degrees
  VAASA               NEW YORK              AZIMUTHS          N. MI.      KM
  63.10 N   21.60 E - 40.72 N   74.00 W    295.58   32.58    3406.9   6309.2
  XMTR  2-30 +  0.0 dBi[default\CCIR.000     ] Az=  0.0 OFFaz=295.6   0.100kW
  RCVR  2-30 2-D Table [default\SWWHIP.VOA   ] Az=  0.0 OFFaz= 32.6
  3 MHz NOISE = -155.0 dBW     REQ. REL = 90%    REQ. SNR = 24.0 dB
  MULTIPATH POWER TOLERANCE =  3.0 dB   MULTIPATH DELAY TOLERANCE =  0.100 ms

   1.0 14.3  2.0  3.0  4.0  5.0  6.0  7.0  8.0  9.0 10.0  0.0  0.0 FREQ
        2F2  4 E  4F2  3F2  3F2  3F2  3F2  3F2  3F2  2F2   -    -  MODE
        7.7  3.0 21.5 13.8 11.0 10.3 10.0 10.1 10.4  3.1   -    -  TANGLE
       22.5 21.3 23.9 22.8 22.4 22.3 22.2 22.2 22.3 21.8   -    -  DELAY
        434   92  380  362  304  289  284  286  292  291   -    -  V HITE
       0.50 1.00 1.00 1.00 1.00 1.00 1.00 0.99 0.94 0.99   -    -  MUFday
        171  203  183  168  158  156  155  154  154  157   -    -  LOSS
        -18  -61  -36  -22  -14   -7   -4   -6   -5   -1   -    -  DBU
       -151 -181 -154 -141 -135 -133 -132 -132 -133 -132   -    -  S DBW
       -171 -144 -149 -152 -154 -156 -158 -159 -161 -163   -    -  N DBW
         20  -37   -5   11   19   23   26   27   28   30   -    -  SNR
         30   81   48   32   24   19   17   17   17   16   -    -  RPWRG
       0.42 0.00 0.00 0.08 0.27 0.46 0.55 0.58 0.60 0.64   -    -  REL
       0.00 0.00 0.00 0.02 0.12 0.24 0.32 0.42 0.00 0.59   -    -  MPROB
       0.20 0.00 0.04 0.11 0.17 0.21 0.24 0.27 0.28 0.27   -    -  S PRB
       25.0 16.4 16.4 16.4 16.4 16.4 16.8 18.5 20.1 21.0   -    -  SIG LW
       25.0  8.3  8.3  8.3  8.3  8.3  8.3  8.8  9.1  8.8   -    -  SIG UP
       25.9 19.8 19.2 18.8 18.4 18.2 18.3 19.7 21.2 22.0   -    -  SNR LW
       25.4 13.3 12.6 12.0 11.6 11.1 10.8 10.9 11.0 10.5   -    -  SNR UP
        0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0   -    -  TGAIN
       -2.0 -7.5  0.0 -0.5 -1.1 -1.2 -1.3 -1.3 -1.2 -7.4   -    -  RGAIN
         -6  -57  -24   -8    0    5    7    7    7    8   -    -  SNRxx

The MUF is 14.3 MHz at 01 UTC, followed by frequencies starting from 2.0 MHz. The output file consists of many pages...

2. Calculating the FOT

If you want to calculate the frequencies of your interest as well as the FOT ("the frequency of optimum traffic", or frequency where MUFday = 0.90), you write as follows:
FREQUENCY  0.00 7.0510.1214.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00

As you can see, the first frequency on the line is zero. What that will do is the output for frequencies:

MUF FOT f1 f2 f3 ...

The start of the result pages would be as follows:

      CCIR Coefficients        ~METHOD 30   VOACAP 03.0724W  PAGE   1

  Jul    2003          SSN =  63.                Minimum Angle= 3.000 degrees
  VAASA               NEW YORK              AZIMUTHS          N. MI.      KM
  63.10 N   21.60 E - 40.72 N   74.00 W    295.58   32.58    3406.9   6309.2
  XMTR  2-30 +  0.0 dBi[default\CCIR.000     ] Az=  0.0 OFFaz=295.6   0.100kW
  RCVR  2-30 2-D Table [default\SWWHIP.VOA   ] Az=  0.0 OFFaz= 32.6
  3 MHz NOISE = -155.0 dBW     REQ. REL = 90%    REQ. SNR = 24.0 dB
  MULTIPATH POWER TOLERANCE =  3.0 dB   MULTIPATH DELAY TOLERANCE =  0.100 ms

   1.0 14.3 11.9  7.1 10.1 14.1  0.0  0.0  0.0  0.0  0.0  0.0  0.0 FREQ
        2F2  2F2  3F2  2F2  2F2   -    -    -    -    -    -    -  MODE
        7.7  3.7 10.0  3.1  6.0   -    -    -    -    -    -    -  TANGLE
       22.5 21.9 22.2 21.8 22.2   -    -    -    -    -    -    -  DELAY
        434  310  284  291  379   -    -    -    -    -    -    -  V HITE
       0.50 0.90 1.00 0.99 0.56   -    -    -    -    -    -    -  MUFday
        171  156  155  157  164   -    -    -    -    -    -    -  LOSS
        -18   -1   -4   -1  -10   -    -    -    -    -    -    -  DBU
       -151 -136 -132 -132 -143   -    -    -    -    -    -    -  S DBW
       -171 -166 -158 -163 -170   -    -    -    -    -    -    -  N DBW
         20   30   26   30   27   -    -    -    -    -    -    -  SNR
         30   19   16   16   23   -    -    -    -    -    -    -  RPWRG
       0.42 0.62 0.55 0.65 0.56   -    -    -    -    -    -    -  REL
       0.00 0.00 0.33 0.59 0.00   -    -    -    -    -    -    -  MPROB
       0.20 0.29 0.24 0.28 0.26   -    -    -    -    -    -    -  S PRB
       25.0 24.1 16.8 21.1 25.0   -    -    -    -    -    -    -  SIG LW
       25.0  9.0  8.3  8.9 20.0   -    -    -    -    -    -    -  SIG UP
       25.9 24.9 18.3 22.0 25.9   -    -    -    -    -    -    -  SNR LW
       25.4 10.3 10.8 10.6 20.4   -    -    -    -    -    -    -  SNR UP
        0.0  0.0  0.0  0.0  0.0   -    -    -    -    -    -    -  TGAIN
       -2.0 -6.0 -1.3 -7.4 -3.2   -    -    -    -    -    -    -  RGAIN
         -6    5    8    8    1   -    -    -    -    -    -    -  SNRxx

The MUF is 14.3 MHz, the FOT is 11.9 MHz and the rest of the frequencies are my 7.05, 10.12 and 14.05 MHz.

3. Calculating from 2 MHz to the HPF

Lastly, there is an option to calculate from 2.0 MHz to the HPF. The HPF is "the highest possible frequency", or the frequency where the value of MUFday reaches 0.10.

You would put:

FREQUENCY 0

or

FREQUENCY 0 -1

The start of the result pages would be as follows:

      CCIR Coefficients        ~METHOD 30   VOACAP 03.0724W  PAGE   1

  Jul    2003          SSN =  63.                Minimum Angle= 3.000 degrees
  VAASA               NEW YORK              AZIMUTHS          N. MI.      KM
  63.10 N   21.60 E - 40.72 N   74.00 W    295.58   32.58    3406.9   6309.2
  XMTR  2-30 +  0.0 dBi[default\CCIR.000     ] Az=  0.0 OFFaz=295.6   0.100kW
  RCVR  2-30 2-D Table [default\SWWHIP.VOA   ] Az=  0.0 OFFaz= 32.6
  3 MHz NOISE = -155.0 dBW     REQ. REL = 90%    REQ. SNR = 24.0 dB
  MULTIPATH POWER TOLERANCE =  3.0 dB   MULTIPATH DELAY TOLERANCE =  0.100 ms

   1.0 14.3  2.0  3.7  5.5  5.5  7.2  8.9 10.7 12.4 14.1 15.9 17.6 FREQ
        2F2  4 E  3F2  3F2  3F2  3F2  3F2  2F2  2F2  2F2  2F2  2F2 MODE
        7.7  3.0 15.2 10.6 10.5 10.0 10.4  3.2  4.0  6.5  7.7  7.7 TANGLE
       22.5 21.3 23.1 22.3 22.3 22.2 22.3 21.8 21.9 22.3 22.5 22.5 DELAY
        434   92  394  295  294  284  292  296  319  396  434  434 V HITE
       0.50 1.00 1.00 1.00 1.00 1.00 0.95 0.97 0.84 0.54 0.27 0.10 MUFday
        171  203  173  157  157  155  154  157  156  165  187  215 LOSS
        -18  -61  -25  -11  -10   -7   -5   -1   -2  -12  -34  -61 DBU
       -151 -181 -144 -134 -134 -132 -133 -133 -136 -144 -167 -195 S DBW
       -171 -144 -151 -155 -155 -158 -161 -164 -167 -170 -174 -177 N DBW
         20  -37    7   21   21   26   28   31   31   26    7  -18 SNR
         30   81   36   22   21   17   17   16   19   24   44   68 RPWRG
       0.42 0.00 0.04 0.35 0.37 0.54 0.60 0.65 0.63 0.54 0.19 0.02 REL
       0.00 0.00 0.00 0.16 0.17 0.34 0.00 0.58 0.00 0.00 0.00 0.00 MPROB
       0.20 0.00 0.09 0.19 0.20 0.25 0.28 0.28 0.29 0.24 0.11 0.03 S PRB
       25.0 16.4 16.4 16.4 16.4 17.6 20.0 21.5 25.0 25.0 25.0 25.0 SIG LW
       25.0  8.3  8.3  8.3  8.3  8.4  9.1  9.7  9.7 21.8 25.0 25.0 SIG UP
       25.9 19.8 18.9 18.3 18.3 19.0 21.0 22.4 25.8 25.9 26.1 26.3 SNR LW
       25.4 13.3 12.2 11.4 11.3 10.8 10.9 11.2 10.9 22.2 25.3 25.3 SNR UP
        0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0 TGAIN
       -2.0 -7.5 -0.4 -1.2 -1.2 -1.3 -1.2 -7.1 -5.4 -2.8 -2.0 -2.0 RGAIN
         -6  -57  -12    2    3    7    7    8    5    0  -20  -44 SNRxx

Here, the MUF is again 14.3 MHz, the first frequency to the right of the MUF is 2.0 MHz and the last is 17.6 MHz which is the HPF (MUFday = 0.10) at 01 UTC. The HPF is obviously different from hour to hour.

The remaining nine frequencies are "computed on a non-linear scale based on the E-MUF and F-MUF values". This comes from the original IONCAP and can be elaborated by those more knowledgeable in the IONCAP theory. :-)

Thanks to Greg Hand for explaining the FREQUENCY parameters.