The "Conductivity Window" is used to define and/or determine the conductivity segments that match the measured data. It is also used to define the inverse distance field and dielectric constant for the radial.
All of the items on the left hand side of this window are used for automatic computation of the IDF and conductivity segments. The top part of the left side of the window contains the input for the automatic determination function:
Measured Data - Click the button to edit the point datasets. Use the drop down selection box to select the measured data to be used in conductivity determination.
Calculated Inv Field - This is the IDF to be used as the 'first guess' in the calculation routine when the "Determine Field at 1 km" option is selected. This value defaults to the calculated value from the transmitter specification for the study. It should be set to a value that is near what is believed to be the IDF for the radial.
Frequency - The frequency for the station.
Dielectric Constant - Select from 3, 5, 8, 10, 15, and 30. The standard AM groundwave propagation curves that the FCC uses for allocation purposes were computed using a dielectric constant of 15.
Below the inputs section are the computation options:
Determine Field at 1 km from measurements - When selected, the program will determine the IDF for the radial based on measured data using the "Calculated Inv Field" as a starting search point. For this computation only the measured values that are within 3 km of the transmitter site will be considered.
Force Site Conductivity - Use this option to force the program to use a specific conductivity at the transmitter site.
Click the "Calculate Conductivities" button to automatically calculate the conductivity segments (and optionally the IDF for the radial) based on the measured data.
All of the items on the right hand side of the window represent the information that is used when displaying data for this radial on the graph. Field strength curves will be drawn using the specified IDF and dielectric constant. The conductivity segments displayed on the graph will be the ones listed in this part of the window. The user can manually change these values and that change will be reflected on the graph.