Boosting HamCAP Performance: A Step-by-Step Guide

By Jari Perkiömäki OH6BG

This guide outlines the steps to enhance radio propagation predictions in HamCAP by adjusting key settings. These modifications are crucial for high-performing stations equipped with antennas that have a take-off angle of less than 3 degrees. Additionally, if your station operates in a low-noise environment, you will benefit significantly from these adjustments. Please note that this process involves using a hex editor and may not be suitable for all users. Proceed with caution and ensure you are comfortable with advanced editing tools before attempting these modifications.

A big thank-you to the HamCAP author, Alex Shovkoplyas VE3NEA, for the tip!

Before you begin

If you do not have the Windows version of VOACAP installed, follow these instructions:

HamCAP requires the Windows version of VOACAP to function. Download the latest version of VOACAP here.
Consult the HamCAP User Guide: All HamCAP users should familiarize themselves with the HamCAP User's Guide. It provides essential instructions and important information about the program and, in particular, about configuring the absorption model of VOACAP for optimal performance.

Let's proceed with enhancing your HamCAP performance!

Install HamCAP

If you do not have HamCAP installed yet, follow these instructions:

Download HamCAP 1.91 and unzip the package.
Locate the installer, Setup.exe, and double-click it to install HamCAP.
Important: Remember the installation directory, as you'll need it in the next step.

Prepare the HamCAP executable

Create a backup copy

Navigate to the HamCAP installation directory and find HamCap.exe.
Important: Create a copy of HamCap.exe and rename it to HamCap2.exe. All modifications will be made to this copy to protect the original file.

Install a Hex Editor

If you do not have a hex editor installed yet, follow these instructions:

Download and install the latest version of Notepad++.
Install the HEX-Editor plugin:
- In Notepad++, go to Plugins > Plugins Admin...
- Select HEX-Editor from the list and install it.
- Restart Notepad++ to activate the plugin.

Optimize HamCAP settings

In Notepad++, open HamCap2.exe.
Activate the Hex Editor view: Plugins > HEX-Editor > View in HEX.

Important: Edit the text in the right pane (clear text), not the hexadecimal values on the left. When editing, the editor is in INSERT mode. This means that it immediately replaces the old value with the new value that you type in. Place the cursor before the character you want to edit.

Point-to-Point calculations

Locate the following string:
```
SYSTEM       1. 145. 3.00  90. 67.0 3.00 0.10
```
Search for "SYSTEM" in Notepad++:

The location of the characters looks like this:
Modify the string to:
```
SYSTEM       1. 153. 0.10  90. 19.0 3.00 0.10
```
After modification, the characters should look like this:

This modification changes the following values:

Noise level: 145 (Residential) to 153 (Quiet)
Minimum take-off angle: 3.00 to 0.10 (degrees)
Required SNR: 67 to 19 (optional)

Save your changes!

Coverage area maps

Locate the following string:
```
System   :  145     3.000   90   67     3.000     0.100 
```
The location of the characters looks like this:
Modify the string to:
```
System   :  153     0.100   90   19     3.000     0.100
```
After modification, the characters should look like this:

Save your changes.