HDPath Antenna Elevation

Q:  How can I determine the antenna elevations needed for line-of-sight using HDPath™?

A:  TAP systems (Version 5.0.1056 and later) with a Maintenance Subscription date of June 30, 2005 or later, and that include the Antenna Elevation module can use HDPath to compute the required antenna heights.

For example, suppose you have plotted a profile in HDPath:

To compute the required antenna elevation values, click the Antenna Elevation button on the toolbar located at the upper left portion of the HDPath form:

The Antenna Elevation form is displayed:

Note that the initial calculation is made (highlighted near the bottom of the form) showing the required antenna elevation at the right side of the profile, based on the current antenna elevation on the left side of the profile.

If you want to see the results of this calculation on the profile, click the Plot button:

A temporary line-of-sight and Fresnel zone are added to the drawing to illustrate the profile with the new antenna elevation settings.

You can also iterate through a range of elevations for the antenna at the site on the left of the drawing and compute the corresponding values for the antenna at the site on the right side of the drawing

For example, suppose you want to try values for the left side antenna elevation from 10 to 200 meters in 10 meter steps:

When you click the Compute button, an elevation value for the right side site will be computed for each of the left side elevations:

You can select one of the lines on the form and click the Plot button to see that combination of antenna elevations displayed:

If you want to refresh the original profile plot to remove the temporary lines, click the “Draw Profile” button on the toolbar. 

Then you can plot the temporary images on a fresh copy of the profile:

The antenna elevation calculations are based on the Fresnel zone settings (based on the transmitter frequency of the left-side facility), and the current earth curvature value in the Topo Data section of the HDPath form.  You can change these values (which are also used for drawing the profile).

For example, suppose you want to compute the required antenna elevation using an earth curvature value of 1.00 and only the line-of-sight with no Fresnel zone clearance.  (This scenario was employed by one TAP user who needed to compute visual line-of-sight, rather than radio-frequency line-of-sight).

You can change the earth curvature value in the Topo Data section of the form:

You can change the Fresnel settings in the Fresnel section of the form (a Ratio value of 0 causes no Fresnel zone to be used for drawing the profile or computing the antenna elevation):

You can draw the profile with these settings:

When you click the Antenna Elevation button on the toolbar, the value will be computed for the new settings:

Click the Plot button to see the new line-of-sight on the profile:

You also have control over the use of Surface Feature files on the profile.  You can plot the profile without the Surface Features by removing the check from the box in the Surface Features section of the form:

When you draw the profile the Surface Features are not shown:

If you compute the antenna elevation value, it is also computed without the Surface Feature information:

The Clearance value on the Antenna Elevation form can be used to include additional clearance on a path for the calculation:

When the new antenna elevation is plotted on the profile, the additional clearance can be seen:




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