# Textual Circuit Prediction

VOACAP Quick Guide: Home

After you have set all the circuit parameters in the VOACAP main screen, it is time to run the analysis.

Choose Circuit from the Run menu (abbreviated later in these web pages as Run > Circuit). A new window will open, containing a lot of data. The data example below is the start of the prediction for the circuit of Pori (Finland) - Johannesburg (South Africa).

```IONOSPHERIC COMMUNICATIONS ANALYSIS AND PREDICTION PROGRAM
VOACAP   VERSION 01.1210W

1         2         3         4         5         6         7
123456789012345678901234567890123456789012345678901234567890123456789012345

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      200112.00
SUNSPOT    110.
LABEL     YLE PORI            JOHANNESBURG
CIRCUIT   61.47N    21.58E    26.25S    28.00E  S     0
SYSTEM       1. 145. 3.00  90. 67.010.00 0.05
FPROB      1.00 1.00 1.00 0.00
ANTENNA       1    1    2   30     0.000[hfcc\HFBC_218.P15    ]160.0  350.0000
ANTENNA       2    2    2   30     0.000[default\SWWHIP.VOA   ]  0.0    0.0000
FREQUENCY  6.07 7.20 9.7011.8513.7015.3517.7321.6525.89 0.00 0.00
METHOD       30    0
EXECUTE
QUIT

CCIR Coefficients        ~METHOD 30   VOACAP 01.1210W  PAGE   1

Dec    2001          SSN = 110.                Minimum Angle= 3.000 degrees
YLE PORI            JOHANNESBURG          AZIMUTHS          N. MI.      KM
61.47 N   21.58 E - 26.25 S   28.00 E    174.24  356.94    5275.6   9769.6
XMTR  2-30 REC705 #01[hfcc\HFBC_218.P15    ] Az=160.0 OFFaz= 14.2 350.000kW
RCVR  2-30 2-D Table [default\SWWHIP.VOA   ] Az=  0.0 OFFaz=356.9
3 MHz NOISE = -145.0 dBW     REQ. REL = 90%    REQ. SNR = 67.0 dB
MULTIPATH POWER TOLERANCE = 10.0 dB   MULTIPATH DELAY TOLERANCE =  0.050 ms

1.0 13.1  6.1  7.2  9.7 11.9 13.7 15.4 17.7 21.6 25.9  0.0  0.0 FREQ
F2F2 F2F2 F2F2 F2F2 F2F2 F2F2 F2F2 F2F2 F2F2 F2F2   -    -  MODE
4.0  7.6  7.8  3.3  4.0  4.0  7.8  7.8  7.8  7.8   -    -  TANGLE
12.0  7.6  7.8  3.3 12.0 12.0 22.0  4.0  8.0  7.8   -    -  RANGLE
34.4 34.2 34.2 33.9 34.3 34.6 35.2 34.6 35.5 34.9   -    -  DELAY
360  290  297  314  332  387  466  402  574  458   -    -  V HITE
0.50 1.00 0.99 0.95 0.73 0.38 0.12 0.01 0.00 0.00   -    -  MUFday
142  146  143  142  138  145  157  198  268  289   -    -  LOSS
44   35   39   48   47   41   29   -5  -77  -96   -    -  DBU
-87  -90  -87  -84  -83  -90 -102 -143 -212 -233   -    -  S DBW
-167 -153 -156 -162 -165 -168 -169 -171 -173 -176   -    -  N DBW
80   63   69   78   83   78   68   28  -39  -58   -    -  SNR
13   16   12   10   11   16   26   66  133  138   -    -  RPWRG
0.74 0.24 0.57 0.74 0.78 0.70 0.51 0.03 0.00 0.00   -    -  REL
0.00 0.00 0.00 0.64 0.00 0.00 0.00 0.00 0.00 0.00   -    -  MPROB
0.35 0.19 0.28 0.34 0.38 0.33 0.23 0.03 0.00 0.00   -    -  S PRB
25.0  9.7 11.2 19.2 25.0 25.0 25.0 25.0 25.0  9.1   -    -  SIG LW
17.7  4.9  4.9  6.2 11.6 21.5 25.0 25.0 25.0  4.9   -    -  SIG UP
26.7 12.4 13.8 21.2 26.7 26.8 26.8 26.8 26.8 13.3   -    -  SNR LW
18.5  7.6  7.1  7.8 12.7 22.2 25.7 25.7 25.7  7.6   -    -  SNR UP
19.7 21.9 21.9 18.3 19.7 19.7 21.8 21.8 21.8 21.7   -    -  TGAIN
-0.9 -2.1 -1.9 -7.0 -0.9 -0.9  0.0 -5.4 -1.8 -1.9   -    -  RGAIN
54   51   55   57   56   51   41    1  -66  -71   -    -  SNRxx
```

There are 24 blocks by hour in this example prediction. One hour block, as seen above out of 24, contains 14 columns. The first column is the time ("1.0") in UT (Universal Coordinated Time). Hours are centered on the hour. Thus, "1.0" represents the time from 0030 to 0130 UT centered at 0100 UT.

The second column (the data under "13.1", ie. 13.1 MHz) is the predicted median maximum usable frequency (MUF) at that hour. Then follows the 11 user-specified frequency columns (the frequencies are in MHz). In our example, only 9 frequencies have been specified, so two last columns out of 11 are empty. The final column contains 22 parameters that have been calculated for these frequencies in the hour block. The first parameter FREQ indicates the frequency (in MHz) used in calculation.

#### A note about the antenna used in the example

For this general study, a Curtain Array AHR(S) 4/4/1 has been defined but with no design frequency. This means that for every frequency calculated, the design frequency would be set equal to the operating frequency (an idealised antenna). In reality, this situation does not occur. Rarely is one transmitting antenna valid for all frequencies from 6 to 26 MHz. Therefore, you have the ability to define different antennas for different frequency ranges. See Antennas in Setting Up the Parameters.

## VOACAP output parameters

Below you will find brief definitions for the 22 parameters in the final column:

ParameterDefinition
MODEIonospheric path for the most reliable mode (ie. the mode with the highest reliability of meeting the REQ.SNR). For the Short Path Model, the number of hops and mode type [E, F1, F2, Es layers] for the MRM are given, eg. 2F2. For the Long Path Model (not to be confused with the long path circuit!), the mode at the transmitter end and the mode at the receiver end are given, eg. F2F2 in our example above.
TANGLERadiation angle for the MRM (degrees).
RANGLEThe angle at the receive end (for long path model only).
DELAYTime delay for the MRM (milliseconds).
V HITEVirtual height of the MRM (kilometers).
MUFdayFraction of days in the month at that hour that the operating frequency is below the MUF for the MRM.
LOSSMedian system loss for the MRM (dB).
DBUMedian field strength expected at the receiver location (dBu).
S DBWMedian signal power expected at the receiver input terminals (dBW).
N DBWMedian noise power expected at the receiver (dBW).
SNRMedian Signal-to-Noise ratio for power summation of all modes (dB-Hz).
RPWRGRequired combination of transmitter power and antenna gains (in dB) needed (+) or excess (-) to achieve the required reliability.
RELCircuit reliability. Fraction of days per month for which the SNR equals to or exceeds the required SNR (REQ.SNR) at the given hour. In our example above, the REL of 0.78 at 11.9 MHz means that a 67-dB SNR or better can be maintained on 78% (ie. 23 days, see Z Tables) of days per month on 11.9 MHz at 0100 UT.
MPROBProbability of an additional mode within the multi-path tolerances (short path only).
S PRBService probability. The probability that the required reliability will be met. Not completed, do not use.
SIG LWLower decile range for the signal power (dB).
SIG UPUpper decile range for the signal power (dB).
SNR LWLower decile range for the SNR (dB).
SNR UPUpper decile range for the SNR (dB).
TGAINTransmitter antenna gain at TANGLE (dBi).
RGAINReceiver antenna gain at TANGLE or RANGLE (dBi).
SNRxxSignal-to-Noise ratio at the Required Reliability (REQ.REL.). Also known as SNR90, if the REQ.REL. is 90% (dB-Hz).