Whereas Area Studies produce maps showing system performance intended for a dispersed set of system users, Link Studies allow you to plan and predict the performance of engineered point-to-point communications systems. Link systems are designed to communicate information between two distinct points rather than from one point to a broad area of use. To design a link system therefore you must specify the parameters for both the transmit end and the receive end of the link. The Link Systems article gives you the information you need to specify the parameters for your link system.

In the Link Groups dialog box (discussed in the Link Systems articles), you can specify an unlimited number of links but only one of these links can be studied at a time. This is called the focus link and is designated on the Link Details dialog box. You can also set a link’s focus by right clicking on the link line, and in the contextual menu that comes up select either Forward Link or Reverse Link and then choose Focus to set the focus for that link.

When you have designated your focus link, and have set the link parameters the way you want them, you can run the link study by going to Studies>Link Study, or by clicking on the Link Study button in the toolbar menu. The link study will run and present the following dialog box: 

Once the terrain for the path has been extracted from the database, or read from an existing path terrain data file, the program will analyze the path and display the results of that analysis as a path profile plot. This plot includes the radio path, Fresnel zones, elevation and distance scales, and other information. It will also use selected boxes around the path profile to display detailed information about path analysis results.

Zoom with Two Points / Zoom Out

When this button is clicked active in the Link Study dialog, you can highlight a portion of the link path window and zoom in to that section of the link path. Click the button again to zoom back out.

Change TX/RX Height and Auto AGL

This drop-down list allows you to select different options for changing the height of the Tx or Rx antenna. When the Change Tx/Rx Height mode is active you can left-click and drag the link end up or down on the path profile to reset the height of the appropriate antenna. Choosing the Min Tx/Rx Height will set the transmit or receive side antenna to the lowest value that still allows line of sight and first Fresnel zone clearance. The Auto Antenna AGL feature will adjust both the Tx and Rx antenna heights so that the first Fresnel zone for the link is just above any obstruction. If the link has clear line of sight, this will lower the appropriate antennas. If the link is obstructed, it will raise the antennas just high enough for Fresnel zone clearance. 

Add or Modify Clutter Items

When this button is clicked active, you can click a location on the Link Profile to add an obstacle (such as a tree or building) that is not represented in the clutter or building databases. This will bring up a dialog box allowing you to enter the height of the obstacle, then recalculate the link study with the obstacle taken into account.

Flat Earth/Curved Earth Display

By clicking this button, you can toggle the path profile graph between curved earth and flat earth. The curved earth plot will curve the terrain profile and graph according to the K factor you entered on the Propagation Model screen. This display also shows the radio path as a straight line that will "diffract" (bend) over any obstacles if the path is obstructed.

The flat earth display shows the terrain profile and graph with no curvature. Instead, the radio paths are curved according to the three K factors you've selected - one from the Propagation Model screen and the other two K factors entered in the Style dialog. For this display the radio paths will continue through any terrain obstacles that block the path. This may be a more useful display for changing transmit and receive antenna heights to achieve adequate clearance.

Style Options

Click the Style button to bring up the link display style options. Here you can set the color and line type for the line of sight path, fresnel zones, etc including how land use and building data are displayed.

Link drop down and Forward/Reverse button

Clicking the link drop-down list lets you pick a specific link to study without having to exit back to the main map and set a different link as a focus link. Clicking the Forward/Reverse toggle button switches the view between both ends of the link

Link Details

Clicking on the Link Details button opens the Link Details dialog box where you set up detailed information about your link system. The entries in this dialog box are described in detail in the Link Systems article. You can change any of the parameters for the transmitter and receiver on this link, including the coordinate position, frequency, gains and losses, etc. When you exit this dialog box, you will be returned to the Link Study dialog box and a new path analysis using the changes you have made. If you change the location of the link, the program automatically re-extracts terrain data. However, if this happens, any edits you made to your previously displayed profile will be lost.

Propagation Models

If you click on the Propagation Models button in the Link Study dialog, you will be presented with the Propagation Models dialog box. For more information please visit the Propagation Models article. Once again, you can change any of the details of the propagation environment, model type, or statistics. When you exit this dialog box, you will be returned to the Link Study dialog box and a new path analysis using the changes you have made.

K‐Factor Fading Sensitivity

When using diversity antennas on a link, the K-Factor button will run an analysis to show the ground reflection fade depth of the main and diversity antennas at various "k-factors" (effective earth radius).

Saving Link Results to a Report File

You may want to create an ASCII data file containing your link analysis results. You can create this file by clicking on the Report button. After making this selection, a dialog box will appear where you can enter the name of the file and where you want to save your link analysis results data.

Viewing Path Loss Details

If you would like to view a detailed breakdown of the path loss components in your link analysis, you may do so by clicking on the Path Loss button. The report contains the major elements that were used to compute the overall path loss, including the free space path loss and the computed loss over each obstacle if the path is obstructed. If the path is line-of-sight, the location of the reflection point, along with the grazing angle, will be noted. Clutter loss at receiver will also be shown if you have selected one of the clutter loss options in the Propagation Model screen.

Write PDF/Print/Print Setup

Clicking the Write PDF button brings up a Link Study Print Report Setup dialog box which allows you to create a PDF of the Link Study screen including: the path profile plot, the Tx and Rx information sections, link performance section and link statistics information section. From the dialog box, you can input a title for the PDF, a Display Date and whether to print portrait or landscape orientation. You can also select to print/not print entire sections or specific section items. Once you have completed filling in the dialog box, click the OK button to print the PDF.

Clicking the Print button creates a document similar to the PDF, but without options to select what sections or items are printed.

The Print Setup button displays a standard Print dialog box to configure printer options used in conjunction with the Print button.