Evaluate HF Communication Links

STK Pro, STK Premium (Air), STK Premium (Space), or STK Enterprise
You can obtain the necessary licenses for this training by contacting AGI Support at support@agi.com or 1-800-924-7244.

This lesson requires STK 12.1 or newer to complete it in its entirety. It includes new features introduced in STK 12.1.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

Capabilities Covered

This lesson covers the following STK Capabilities:

  • STK Pro
  • Communications
  • Coverage

Problem Statement

Engineers and operators need to quickly determine high frequency (HF) communication link budgets. Skywave propagation, sunlight / darkness at the site of transmission and reception, season, sunspots, and solar activity are some factors needed to be taken into consideration. In this lesson, engineers will perform three analyses in the following order:

  1. Analyze a near vertical incidence skywave (NVIS)
  2. Analyze a long distance communication link
  3. Analyze long distance communications in a large coverage area

Solution

  • Use STK Pro and STK's Communications and Coverage capabilities to model and analyze HF communications between two ground sites divided by mountainous terrain.
  • Next, model and analyze HF communications between two ground sites separated by thousands of kilometers.
  • Finally, determine HF communication coverage over a large operations area.

What you will learn

Upon completion of this tutorial, you will understand the following:

  • The VOACAP Radio Frequency Environmental Model
  • VOACAP Data Providers
  • Dipole and External Antenna Patterns

In this tutorial, antenna design frequencies won't always match the actual transmission or received frequencies. Antenna lengths in this scenario simulate multiband antennas.

Video Guidance

Watch the following video. Then follow the steps below, which incorporate the systems and missions you work on (sample inputs provided).

Create a new scenario

Create a new scenario for a twenty four (24) hour time period starting 21 Sept 2020 19:00:00.000 UTCG.

  1. Launch STK ().
  2. In the Welcome to STK window, click Create a Scenario.
  3. Enter the following in the New Scenario Wizard:
    4. Option Value
    Name: HF_Analysis
    Location: Default
    Start: 21 Sep 2020 19:00:00.000 UTCG
    Stop: 22 Sep 2020 19:00:00.000 UTCG
  4. When you finish, click OK.
  5. When the scenario loads, click Save (). A folder with the same name as your scenario is created for you in the location specified above.
  6. Verify the scenario name and location and click Save.

    7. Save Often!

Declutter the labels

Label Declutter is used to separate the labels on objects that are in close proximity for better identification in small areas.

  1. Bring the 3D Graphics window to the front.
  2. Open the 3D Graphics window properties ().
  3. On the Details page, locate the Label Declutter section.
  4. Select Enable.
  5. Click OK to accept the changes and close the Properties Browser.

RF environment

A scenario's RF Environment properties enable you to model environmental factors that can affect the performance of a communications link. They are set at the scenario level and can be overridden or varied at the individual STK object level.

  1. Right-click on HF_Analysis () and select Properties ().
  2. Select the RF - Environment page.
  3. Select the Atmospheric Absorption tab.

VOACAP

VOACAP (Voice of America Coverage Analysis Program) is a professional high-frequency propagation prediction software from Naval Research Laboratory and the Institute for Telecommunications Sciences (ITS), originally developed for Voice of America (VOA). STK offers an enhanced solution for communications modeling at High Frequency (HF) by introducing off-the-shelf interoperability with VOACAP.

  1. Enable Use.
  2. Click the ellipsis button (Component Selector) () beside the Type field.
  3. In the Select Component window, select VOACAP.
  4. Click OK.

VOACAP parameters

For this scenario, use the default VOACAP parameters except for Sun Spot Number and Compute Alternative Frequencies.

  • The predicted sunspot number for this analysis is 5. The actual sunspot number or predicted number can be queried at websites such as Australian Government - Bureau of Meterorology, Space Weather Services or SpaceWeatherLive.
  • Select Compute Alternative Frequencies to execute the VOACAP model using the transmit frequency and 10 other frequencies spread across the HF band. The 10 frequencies are logarithmically spread across the HF band from 2 Hz to 30 MHz.
  1. Change the Sun Spot Number: value to 5.
  2. Enable Compute Alternative Frequencies.
  3. Click OK to accept the changes and close the Properties Browser.

Near vertical incidence skywave (NVIS)

NVIS radio waves travel near-vertically upwards into the ionosphere where they are refracted back down and can be received within a circular region up to 650 kilometers (km) from the transmitter. The first analysis is between two sites that are approximately 60 km apart. They are separated by a mountain range.

NVIS transmitter site

The transmitter site sits in high desert.

  1. Using the Insert STK Objects Tool, insert a Place () object using the From City Database method.
  2. When the Search Standard Object Data window opens, in the Name: field, enter Palmdale.
  3. Click Search.
  4. In the Results: field, select Palmdale California.
  5. Click Insert.
  6. Click Close.

NVIS transmitter

  1. Using the Insert STK Objects Tool, insert a Transmitter () object using the Insert Default method.
  2. When the Select Object window opens, select Palmdale.
  3. Click OK.
  4. Rename the Transmitter () object NVIS_HF_Tx.

Use a Complex Transmitter model

The Complex Transmitter model allows you to select among a variety of analytical and realistic antenna models, and to define the characteristics of the selected antenna type.

  1. Open NVIS_HF_Tx's () properties ().
  2. On the Basic - Definition page, click the ellipsis button (Component Selector) () beside the Type field.
  3. When the Select Component window opens, select Complex Transmitter Model.
  4. Click OK.
  5. On the Model Specs tab, set the following:
    6. Option Value
    Frequency: 0.010 GHz (10 MHz)
    Power: 1 w (1 Watt)
    Data Rate: 5 Mb/sec
  6. Click Apply to accept the changes and keep the Properties Browser open.

NVIS transmitter antenna

Dipole antennas are modeled analytically, using modeling equations that can be found in standard antenna texts. The NVIS transmitter antenna's design frequency covers a range of frequencies from 3 MHz through 10 MHz.

  1. Select the Antenna tab.
  2. Click the ellipsis button (Component Selector) () beside the Type field.
  3. When the Select Component window opens, select Dipole.
  4. Click OK.
  5. Set the following:
    6. Option Value
    Design Frequency: 0.0065 GHz
    Length: 23 m
    Efficiency: 80 %
  6. Click Apply to accept the changes and keep the Properties Browser open.

Antenna orientation

In STK, the default orientation for a dipole antenna is vertical. Change this to horizontal.

  1. Select the Orientation sub-tab on the Antenna tab.
  2. Change the Elevation: value to 0 deg.
  3. Click Apply to accept the changes and keep the Properties Browser open.

Line of sight (LOS) constraint

Since VOACAP is an over the horizon model, the LOS constraint should be turned off. If the LOS constraint is not turned off there will be no access intervals.

  1. Select the Constraints - Basic page.
  2. Turn off Line of Sight.
  3. Click OK to accept the changes and close the Properties Browser.

NVIS receiver site

The receiver site is located approximately 60 km away and lies in a basin near the ocean. Mountains separate the receiver site from the transmit site.

  1. Using the Insert STK Objects Tool, insert a Place () object using the From City Database method.
  2. When the Search Standard Object Data window opens, enter Los Angeles in the Name: field.
  3. Click Search.
  4. In the Results: field, select Los Angeles, California.
  5. Click Insert.
  6. Click Close.

NVIS receiver

  1. Using the Insert STK Objects Tool, insert a Receiver () object using the Insert Default method.
  2. When the Select Object window opens, select Los_Angeles.
  3. Click OK.
  4. Rename the Receiver () object NVIS_HF_Rx.

Use a complex receiver model

The Complex Receiver model allows you to select among a variety of analytical and realistic antenna models, and to define the characteristics of the selected antenna type.

  1. Open NVIS_HF_Rx's () properties ().
  2. Click the ellipsis button (Component Selector) () beside the Type field.
  3. When the Select Component window opens, select Complex Receiver Model.
  4. Click OK.

NVIS receiver antenna

The NVIS receiver antenna has the same setup as the NVIS transmitter antenna.

  1. Select the Antenna tab.
  2. Click the ellipsis button (Component Selector) () beside the Type field.
  3. When the Select Component window opens, select Dipole.
  4. Click OK.
  5. Set the following;
    6. Option Value
    Design Frequency: 0.0065 GHz
    Length: 23 m
    Efficiency: 80 %
  6. Click Apply to accept the changes and keep the Properties Browser open.

Antenna orientation

  1. Select the Orientation sub-tab on the Antenna tab.
  2. Change the Elevation: value to 0 deg.
  3. Click Apply to accept the changes and keep the Properties Browser open.

LOS constraint

  1. Select the Constraints - Basic page.
  2. Turn off Line of Sight.
  3. Click OK to accept the changes and close the Properties Browser.

3D Graphics window view

As stated earlier, a mountain range separates the two ground sites and that's why you are testing communications using an HF transmitter and receiver.

  1. Bring the 3D Graphics window to the front.
  2. Zoom To Los_Angeles ().
  3. Use your mouse to obtain a view of Los_Angeles (), the mountains and Palmdale () in the distance.

Los AngEles, Mountains and Palmdale

Create an access

To determine the performance of the communication link between Los Angeles and Palmdale, create an access between the transmitter and the receiver.

  1. In the Object Browser, right click on NVIS_HF_Tx () and select Access ().
  2. When the Access Tool opens, in the Associated Objects list, expand () Los_Angeles ().
  3. Select NVIS_HF_Rx ().
  4. Click Compute ().
  5. On the lower right hand side of the Access Tool (), click Report & Graph Manager...

Comm Link - HF

Creating an HF link budget report in STK combines Link Information VOACAP Data Providers and Link Information Data Providers. This information can be found in STK Help Data Providers by Object. The Comm Link - HF report contains a lot of information. For the purposes of this tutorial, you will focus on a couple of the data providers.

STK samples the HF link in one (1) hour increments. There are a couple of ways to approach this. You can use the default time step (60 seconds) in the report and then change the time step when the report opens, or you can change the time properties step size prior to creating a report. Do the latter.

  1. In the Report & Graph Manager Time Properties section, enable Specify Time Properties.
  2. Enable Use step size / time bound.
  3. Change the Step size: value to 1 hr.
  4. In the Installed Styles list, select Comm Link - HF.
  5. Click Generate.

Interpreting the data providers

The Skywave Mode represents the number of hops and the layers from which the hops have occurred. For example, 1F2 means there was one hop and the F2 layer was responsible for the hop.

  1. Locate the SkywaveTransmit Elevation column. It is the angle of the sky-wave signal path.
  2. Locate the Skywave Mode column. There is a combination of F2 and E ionosphere layers being used.
  3. Locate the Rcvd. Iso. Power (dBW) column. This is the received power before gain. You want a value higher than -150.000.
  4. Locate the C/N (dB) column. You have poor carrier to noise ratio over the analysis period.
  5. Leave the Comm Link - HF report open.
  6. Return to the Report & Graph Manager.

Comm Link - VOACAP files

The Comm Link - VOACAP Files report contains a lot of information and is similar to Textual Circuit Prediction found on the VOACAP website. If you recall, during the initial VOACAP setup, you turned on Compute Alternative Frequencies. Since the link information received isotropic power and carrier to noise ratio are poor, use the Comm Link - VOACAP report to improve the link.

  1. In the Installed Styles list, select Comm Link - VOACAP Files.
  2. Click Generate.
  3. When the VOACAP Files window opens, leave the default Time: value.
  4. Click OK.
  5. When the Comm LInk - VOACAP report generates, scroll down the report to the Output File.

VOACAP Output

Transmit frequency adjustment

The antennas on both the transmitter and receiver are designed for a frequency range of 3 - 10 MHz. This eliminates any frequencies above and below that range. You may want to focus on a frequency that has a high transmit angle (TANGLE) but a short time delay (DELAY). Look for the best signal to noise ratio (SNRxx). This is just a sample, but for now, that will be your focus. The frequency 4.9 MHz provides a good starting point.

  1. Open NVIS_HF_Tx's () properties ().
  2. On the Basic - Definition page, change the Frequency: value to 0.0049 GHz.
  3. Click OK to accept the changes and close the Properties Browser.
  4. Return to the Comm Link - HF report.
  5. Refresh () the report.
  6. Locate the Skywave Mode column. The ionosphere E layer is no longer being used.
  7. Locate the Rcvd. Iso. Power (dBW) column. All values are above -150.000.
  8. Locate the C/N (dB) column. There is a significant improvement.

    9. Something interesting to note in the C/N (dB) column are the fluctuations in values. Your values are lowest during the hours of darkness and they are low around noon local time (19:00:00 (UTCG) is noon, 07:00:00 (UTCG) is midnight).

  9. When finished, close all reports, the Report & Graph Manager, and the Access Tool.
  10. Click on Analysis in the menu bar.
  11. Select Remove All Accesses.

Low-angle long-range skywaves

When high-frequency signals enter the ionosphere at a low angle they are bent back towards the earth by the ionized layer. If the peak ionization is strong enough for the chosen frequency, a wave will exit the bottom of the layer earthwards. The Earth's surface then reflects the descending wave back up again towards the ionosphere. When operating at frequencies just below the maximum usable frequency (MUF), losses can be quite small. The radio signal could skip between the earth and ionosphere multiple times (multi-hop propagation). Signal power of only a few Watts can sometimes be received thousands of kilometers away.

Long-range transmitter

The long range communications link is between Los Angeles and Landstuhl, Germany.

  1. Using the Insert STK Objects Tool, insert a Transmitter () object using the Insert Default method.
  2. When the Select Object window opens, select Los_Angeles ().
  3. Click OK.
  4. Rename the Transmitter () object LR_HF_Tx.
  5. Open LR_HF_Tx's () properties ().

Use a complex transmitter model

  1. Open LR_HF_Tx's () properties ().
  2. On the Basic - Definition page, click the Type: ellipsis.
  3. When the Select Component window opens, select Complex Transmitter Model.
  4. Click OK.
  5. In the Model Specs tab, set the following:
    6. Option Value
    Frequency: 0.02 GHz
    Power: 50 dBW
    Data Rate: 1 Mb/sec
  6. Click Apply to accept the changes and keep the Properties Browser open.

Long-range transmitter antenna

You want to use a custom antenna pattern for your analysis. Communications allows you to specify an external antenna pattern file that contains user defined data. You will use a PhiTheta external antenna pattern file formatted to the specifications of your antenna.

  1. Select the Antenna tab.
  2. Click the ellipsis button (Component Selector) () beside the Type field.
  3. When the Select Component window opens, select External Antenna Pattern.
  4. Click OK.
  5. Click the External Filename: ellipsis button ().
  6. Browse to C:\Program Files\AGI\STK 12\Data\Resources\stktraining\samples.
  7. Select VOACAP.pattern.
  8. Click Open.
  9. Set the Design Frequency: value to 0.015 GHz.
  10. Click Apply to accept the changes and keep the Properties Browser open.

Antenna orientation

The antenna is directional.

  1. Select the Orientation sub-tab on the Antenna tab.
  2. Change the Azimuth: value to 65 deg. This will boresite the pattern in the general direction of the receiver.
  3. Click Apply to accept the changes and keep the Properties Browser open.

LOS Constraint

  1. Select the Constraints - Basic page.
  2. Turn off Line of Sight.
  3. Click OK to accept the changes and close the Properties Browser.

Long-range receiver site

  1. Using the Insert STK Objects Tool, insert a Place () object using the From City Database method.
  2. When the Search Standard Object Data window opens, in the Name: field, enter Landstuhl.
  3. Click Search.
  4. In the Results: field, select Landstuhl.
  5. Click Insert.
  6. Click Close.

Long-range receiver

  1. Using the Insert STK Objects Tool, insert a Receiver () object using the Insert Default method.
  2. When the Select Object window opens, select Landstuhl ().
  3. Click OK.
  4. Rename the Receiver () object LR_HF_Rx.

Use a complex receiver model

  1. Open LR_HF_Rx's () properties ().
  2. Click the ellipsis button (Component Selector) () beside the Type field.
  3. When the Select Component window opens, select Complex Receiver Model.
  4. Click OK.

Long-range receiver antenna

The long range receiver uses a dipole antenna. Its design frequency covers a range of frequencies from 10 MHz through 30 MHz.

  1. Select the Antenna tab.
  2. Click the ellipsis button (Component Selector) () beside the Type field.
  3. When the Select Component window opens, select Dipole.
  4. Click OK.
  5. Set the following:
    6. Option Value
    Design Frequency: 0.02 GHz
    Length: 9 m
    Efficiency: 80 %
  6. Click Apply to accept the changes and keep the Properties Browser open.

Antenna orientation

The dipole antenna is horizontal.

  1. Select the Orientation sub-tab on the Antenna tab.
  2. Change the Elevation: value to 0 deg.
  3. Click Apply to accept the changes and keep the Properties Browser open.

LOS Constraint

  1. Select the Constraints - Basic page.
  2. Turn off Line of Sight.
  3. Click OK to accept the changes and close the Properties Browser.

Create an access

Create an access between the long range transmitter and receiver.

  1. In the Object Browser, right click on LR_HF_Tx () and select Access ().
  2. When the Access Tool opens, in the Associated Objects list, expand () Landstuhl ().
  3. Select LR_HF_Rx ().
  4. Click Compute ().
  5. Click Report & Graph Manager.

Comm Link - HF

Determine the link performance.

  1. In the Report & Graph Manager Time Properties section, enable Specify Time Properties.
  2. Enable Use step size / time bound.
  3. Change the Step size: value to 1 hr.
  4. In the Installed Styles list, select Comm Link - HF.
  5. Click Generate.

Interpret the data providers

  1. Locate the Skywave Transmit Elevation column. The transmit elevations are much lower than the NVIS elevations.
  2. Locate the Skywave Mode column. The link experiences multi-hop propagation in the ionosphere F layer.
  3. Locate the Rcvd. Iso. Power (dBW) column. You want values higher than -150.000.
  4. Locate the C/N (dB) column. You have poor carrier to noise ratios.
  5. Leave the Comm Link - HF report open.
  6. Return to the Report & Graph Manager.

Comm Link - VOACAP files

Use the Comm Link - VOACAP report data to improve the link.

  1. In the Installed Styles list, select Comm Link - VOACAP Files.
  2. Click Generate.
  3. When the VOACAP Files window opens, change the time to 22 Sep 2020 03:00:00.000. Both ground sites are dark at this time and you want to pick a frequency that improves communications during this period.
  4. Click OK.
  5. When the Comm Link - VOACAP report generates, scroll down the report to the Output File.

Transmit frequency adjustment

The antennas on both the transmitter and receiver are designed for a frequency range of 10 - 30 MHz. This eliminates any frequencies below that range. You may want to focus on a frequency that has a low transmit angle (TANGLE) and a short time delay (DELAY). Look for the best signal to noise ratio (SNRxx). This is just a sample, but for now, that will be your focus. The frequency 12.2 MHz provides a good starting point. Note the SNRxx values in the lower frequency range. Lower frequencies work better at night.

  1. Open LR_HF_Tx's () properties ().
  2. On the Basic - Definition page, change the Frequency: value to 0.0122 GHz.
  3. Click OK.
  4. Return to the Comm Link - HF report.
  5. Refresh () the report. Keep in mind that it could be daylight in Los Angeles and night time in Landstuhl or vice versa.
  6. Locate the Skywave Transmit Elevation (deg) column. For the most part, daylight transmission elevation angles have increased.
  7. Locate the Skywave Mode column. Multi-hop propagation is still in effect.
  8. Locate the Rcvd. Iso. Power (dBW) column. Many values are now above -150.000.
  9. Locate the C/N (dB) column. There is a significant improvement.

    10. This is just an example and there are other losses and gains affecting the link such as skywave transmit gain and skywave range. The combination of skywave loss and skywave free space loss greatly affect the link.

  10. When finished, close all reports, the Report & Graph Manager, and the Access Tool.
  11. Click on Analysis in the menu bar.
  12. Select Remove All Accesses.

Wide area coverage

You have analyzed an NVIS communication link and a long range communication link. Now we will analyze communications in a large geographical area. The Coverage Definition object defines a coverage areas for analysis.

  1. Using the Insert STK Objects tool, insert a Coverage Definition () object using the Insert Default method.
  2. Rename CoverageDefinition1 () HF_VOACAP_Cov.

Define the coverage grid

Start by defining the coverage grid. Coverage analyses are based on the accessibility of assets (objects that provide coverage) and geographical areas.

  1. Open HF_VOACAP_Cov's () properties ().
  2. Change Grid Area of Interest - Type: to LatLon Region.
  3. Set the following:
    4. Option Value
    Min. Latitude: -35 deg
    Min. Longitude: -20 deg
    Max. Latitude: 65 deg
    Max. Longitude: 90 deg
  4. Set Grid Definition - Point Granularity to 4 deg.
  5. Change Point Altitude to Altitude above Terrain.
  6. Click Apply to accept the changes and keep the Properties Browser open.
  7. Bring the 2D Graphics window to the front.
  8. Center the map over the coverage grid.

Coverage Grid

Apply a grid constraint

LR_HF_Rx () contains the constraint you want to apply to the coverage grid.

  1. Return to HF_VOACAP_Cov's () properties ().
  2. On the Basic - Grid page, click Grid Constraint Options.
  3. When the Grid Constraints Options window opens, set the Reference Constraint Class: to Receiver.
  4. In the Use Object Instance list, select Landstuhl/LR_HF_Rx.
  5. Click OK to close the Grid Constraints Options window.
  6. Click Apply to accept the changes and keep the Properties Browser open.

Coverage assets

Assets properties allow you to specify the STK objects used to provide coverage.

  1. Select the Basic - Assets page.
  2. In the Assets field, select LR_HF_Tx ().
  3. Click Assign.
  4. Click Apply to accept the changes and keep the Properties Browser open.

Automatically recompute accesses

STK automatically recomputes accesses every time an object on which the coverage definition depends (such as an asset) is updated. If you want control as to when coverage is computed, you need to turn this off.

  1. Select the Basic - Advanced page.
  2. Clear Automatically Recompute Accesses.
  3. Click Apply to accept the changes and keep the Properties Browser open.

Remove the visual grid

You don't need to see the grid on the 2D and 3D Graphics windows.

  1. Select the 2D Graphics - Attributes page.
  2. Clear Show Points.
  3. Click OK to accept the changes and close the Properties Browser.

Compute accesses tool

The ultimate goal of coverage is to analyze accesses to an area using assigned assets and applying necessary limitations upon those accesses.

  1. In the Object Browser, select HF_VOACAP_Cov ().
  2. Click CoverageDefinition in the menu bar.
  3. Select Compute Accesses.
  4. Notice the progress bar in the lower right corner of STK.

Figure of merit

STK allows you to specify the method by which the quality of coverage is measured using a Figure Of Merit () object.

  1. Using the Insert STK Objects tool, insert a Figure Of Merit () object using the Insert Default method.
  2. When the Select Object window opens, select HF_VOACAP_Cov ().
  3. Click OK.
  4. Rename the Figure Of Merit () object Rcvd_Iso_Pwr.

Measuring access constraints

Access Constraints measure the value of various constraint parameters used to define visibility within STK.

  1. Open Rcvd_Iso_Pwr's () properties ().
  2. On the Basic - Definition page, set the following Definition values:
    3. Option Value
    Type: Access Constraint
    Constraints: RcvdIsotropicPower
    Compute: Maximum
    Time Step: 3600 sec
  3. Click Apply to accept the changes and keep the Properties Browser open.

Overall Value by Time data provider

The Overall Value by Time Data Provider reports statistical information on time dependent values. Statistics are generated by sampling values from all grid points at the reported times.

  1. In the Object Browser, right click on Rcvd_Iso_Pwr ().
  2. Select Report & Graph Manager.
  3. In the Installed Styles list, select the Grid Stats Over Time graph.
  4. Click Generate. Be patient, this can take a few minutes.

    5. Grid Stats Over Time Graph

    You can use the graph to quickly find the lowest and highest received isotropic power (dBW) values during the 24 hour analysis.

  5. Place your cursor over the lowest minimum point in the graph (approximately -492 (dBW)).
  6. Place your cursor over the highest maximum point in the graph (approximately -100 (dBW)).

    7. You will use these values to create contours on your 2D and 3D Graphics windows.

  7. Close the Grid Stats Over Time graph and the Report & Graph Manager.

Define animation graphics for the Figure Of Merit

The Animation page enables you to define animation graphics for the Figure Of Merit.

  1. Return to Rcvd_Iso_Pwr's () properties ().
  2. Select the 2D Graphics - Animation page.
  3. Set the Filled Area - % Translucency: value to 50.
  4. Enable Show Contours and set the following:
    5. Option Value
    Start: -500 dBW
    Stop: -100 dBW
    Step: 50 dBW
  5. Click Add Levels.
  6. Ensure Color Method: is set to Color Ramp.
  7. If required, set Start Color: to red and End Color: to blue.
  8. Click Apply. Be patient. This could take a minute or two.
  9. Click Legend.
  10. When the Animation Legend opens, click Layout and set the following in the Figure of Merit Legend Layout:
    11. Option Value
    2D Graphics Window - Show at Pixel Location enabled
    3D Graphics Window - Show at Pixel Location enabled
    Text Options - Title: Rcvd Isotropic Pwr (dBW)
    Text Options - Number Of Decimal Digits: 0
    Range Color Options - Color Square Width (pixels): 60
  11. Click OK.
  12. Close the floating Animation Legend window.
  13. Click OK to accept the changes and close the Properties Browser.

2D Graphics window contours view

Although you can view the received isotropic power (dBW) contour in both the 2D and 3D Graphics windows, due to the large geographic coverage area, it is easier to see in the 2D Graphics window.

  1. Bring the 2D Graphics window to the front.

    2. 2D Graphics Window Animation Contours

  2. Using the Animation Toolbar, increase () the Time Step: value to 3600 sec.
  3. Use Step Forward () to animate the scenario, one (1) time step at a time. Be patient. Each step forward could take a while to render the next view.

Save your work

  1. Save () your work.

Summary

During this tutorial, three HF analyses were performed:

  1. The first analysis took place between to sites, approximately 60 kilometers apart, using a high angle skip. Horizontal dipole antennas were employed at both sites. After analyzing the first link, using VOACAP files, you determined a lower frequency was required which significantly improved communications.
  2. The second analysis featured a long distance, low angle, multi-hop propagation that featured an external directional antenna pattern on the transmitter and a dipole receiver antenna. Again, using VOACAP files, you lowered the frequency and improved the communications link.
  3. The third analysis used the long distant transmitter and receiver to perform wide area coverage, focusing on received isotropic power.

On your own

Throughout the tutorial, hyperlinks were provided that pointed to in depth information concerning Transmitter () and Receiver () objects. Now's a good time to go back through this tutorial and view that information. Open the VOACAP.pattern file with Notepad to understand the setup of the external antenna pattern. Go to the different receivers and transmitters properties and open the 3D Graphics - Attributes pages. Turn on and view Volume Graphics - Show Volume to view the antenna pattern in the 3D Graphics window. Try using vertical vice horizontal dipole antennas. Adjust the azimuth of the long range transmitter's antenna, and see how that affect coverage.