TAP Transmission Line Data Base Overview

The TAP transmission line data base refers to a set of Microsoft FoxPro version 2.5 tables found in the LINES\ sub-directory of your TAP program directory. This set of files will include as many as six different files for each library of transmission lines depending upon the manner in which the library was created. All line files must be located in a sub-directory named \LINES under your TAP working directory. You can use the Transmission Line Files Editor to view, add to or modify antenna patterns in these files or create and edit a new set of line files.

Files such as LMSAND00.DBF that begin with the letters "LMS" a description for each line in the library. Files such as LNDAND00.DBF that begin with the letters "LND" contain the frequency and attenuation values for each line used by the Transmission Line Loss Lookup program to calculate line loss. The LMSXXXXX.CDX and LNDXXXXX.CDX files are the associated index files for the line data base. If you created a new line data base using the transmission line editor, you will notice an "INF" file such as LMSXXXXX.INF that was automatically generated for each of the transmission line tables referenced above.

The data included in the transmission line files supplied with TAP contain manufacturing specifications supplied by transmission line vendors, and SoftWright does not warrant the accuracy of the data nor the availability of line products.

Viewing Transmission Line Parameters

In this tutorial, you will view transmission line types and their associated parameters in the Transmission Line Files Editor.

1. From the main menu of TAP, use your left mouse button to click on the Editors menu, then on the Transmission Line Files option.
   
1. This will display the Open File dialog. Use your left mouse to select a line library file from the list of available files. In this case, we select the Andrew transmission line library and press OK.
   
1. When the TAP Transmission Line Files Editor appears, it will display the lines in alphabetical order according to Line Type. In our case, the "Andrew EW127A Elliptical Waveguide, 11.7-13.25 GHz" line appears first. We will move to a different line in the library.
   
1. Press the Find button at the bottom of the editor.
   
1. When the Find screen appears, pull down the Record Selection List to view a list of transmission lines.
   
   
1. Use your left mouse on the vertical scroll bar to navigate to the "Andrew LDF5-50A 7/8" Foam Dielectric 50-ohm" line as we have done.
   
   
1. When this line appears in the Record Selection List press the Select button to reposition the editor to this record.
   
1. Press Close to terminate the Find program.
   
1. Confirm that the Andrew LEF5-50A line is displayed in the editor. Now select the Parameters Editor tab folder.
   
1. When you move to the parameters tab, only the existing parameters records for the CURRENT line type are displayed in the Parameters Editor grid. If you return to the specifications tab and move to a different line, the parameters that are displayed the next time you view the Parameters Editor are likely to differ. You can make modifications to the transmission line parameters records directly in the Parameters Editor grid. All changes to the parameters grid cells are immediately written to the underlying line parameters file without the need to Save your edits. Freq refers to frequency in MHz. Atten is attenuation in dB/100 feet. Power is the average power rating in kilowatts. Veloc is the velocity of propagation percentage.
   
1. You can use the TAP Sort Order functions to help you analyze your data. For example, use your left mouse to pull down the sort order list next to the Sort by Atten button in the Sort Order frame. Press the Sort by Atten button to sort your line parameters in ascending order by attenuation. You can see that the 5000 MHz record has the highest attenuation value in the file.

Creating a New Transmission Line

1. Now press the Line Specs tab to view the line description again. From the Line Specifications tab folder, press the New button.
   
1. TAP will insert a description in the Line Type field. The white background of the text box is a reminder that you are in "edit" mode.
   
1. Replace the Line Type description with "Transmission Line Tutorial" as we have done below.
   
1. Press the Save button to record these changes in the line library.
   
1. Now press the Parameters Editor tab.
   
1. There are currently no field records specified. We will use the New button to add a range of records to the grid. The values we are about to enter are purely fictional in an attempt to simplify the data entry aspects of this tutorial. Press the New button.
   
1. TAP will automatically add a record to the grid and position the record pointer to this record. A default value of 100.0 MHz is specified for each FREQ value. We will modify the frequency and attenuation parameters in this tutorial. In an attempt to streamline this tutorial, we will not edit the average power and velocity of propagation fields.
   
1. We will add a total of 20 records to the line parameters file for our tutorial line. Press the New button repeatedly until the editor frame title displays "20 Records Specified" as ours does below.
   
1. Use your scroll bar to move to the top of this file. Position your cursor in the frequency (FREQ) cell of the second record as we have done.
   
1. Change the frequency field value (FREQ) from 100 to 200 MHz.
   
1. In the same way, edit records 3 to 13 as we have done below. In an effort to keep this tutorial as simple as possible, you will notice that we simply increment each field value by 100 MHz.
   
1. Move the vertical scroll bar to the bottom of the grid making the remaining records accessible. Edit the frequencies as we have done. Verify that your frequency range is now 100 MHz to 2 GHz.
   
1. Use the vertical scroll bar to move to the top of the grid and position your cursor in the attenuation (ATTEN) column of the 100 MHz record.
   
1. Change the attenuation from 0.0 to 0.1.
   
1. Change the attenuation values (ATTEN) for frequencies 200 to 1300 MHz as we have done below. In order to simplify this tutorial, you will notice that the attenuation value is simply the frequency multiplied by 0.001.
   
1. Move the vertical scroll bar to the bottom of the grid making the remaining records accessible.
   
1. Beginning with the 1400 MHz record, edit the frequencies as we have done. Verify that your attenuation range is now 0.1 to 2.0 dB/100 ft. We have finished editing the Transmission Tutorial line parameters.
   
1. When you are ready to continue with this tutorial move to the Line Specifications tab. Press the Close button. Our next step is to demonstrate how we might use this transmission line.

Calculating Transmission Line Loss

In this part of the tutorial, you will use the TAP Transmission Line Loss Lookup program to calculate line loss for the transmission line we just created.

1. From the main menu of TAP, use your left mouse button to click on the Utilities menu, then on the Transmission Line Loss option.
   
1. This will display the Open File dialog. Use your left mouse to select a line library file from the list of available files. In this case, we select the Andrew transmission line library and press OK.
   
1. When the TAP Transmission Line Loss screen appears, it will display the lines in alphabetical order according to Line Type. In our case, the "Andrew EW127A Elliptical Waveguide, 11.7-13.25 GHz" line appears first. We will move to a different line in the library.
   
1. Move the vertical scroll down until the "Transmission Line Tutorial" line is visible and select it with your left mouse.
   
1. Notice that the frequency range for this antenna is 100 to 2000 MHz as expected. Because the Frequency (MHz) text box does not contain a value within this range, the Attenuation label reads "FREQ OUT OF RANGE".
   
1. Enter a Frequency between 100 MHz and 2 GHz such as 450 MHz. Enter a Line Length of 50 ft. Your screen should look like ours below.
   
1. TAP calculates a line loss of 0.45 dB for 100 ft of tutorial transmission line. The calculated Efficiency is 90.16%. Average Power and Velocity of Propagation are zero because our sample line records do not contain data for these parameters.
   
1. This concludes our tutorial. In practice, you will obtain the manufacturer’s specifications for your transmission line and add realistic line parameters. One final note. For convenience, we have added our tutorial line parameters to the Andrew transmission line library. You may wish to remove the tutorial line from the Andrew library to avoid future confusion. In order to accomplish this, after closing this lookup program, run the Transmission Line Files Editor again and delete the "Transmission Line Tutorial" line. Press Close to end the lookup program.