W8WWV - N2PK VNA - gnat: VNA Test Program

Greg Ordy

What is gnat?

gnat, Greg's Network Analyzer Test program, is a small test program that interacts with the N2PK VNA at the hardware abstraction level. gnat can control the RF and LO DDS chips, and retrieve readings from the ADC (analog to digital converter). These sort of operations are useful when testing and/or debugging a VNA board. gnat does not measure impedance or other computed electrical properties. It is a direct link to the hardware, nothing more.

gnat is a Windows program, and it is built upon the VNAccess DLL (dynamic link library). The DLL is automatically downloaded with the gnat executable

Main gnat Window

gnat has the following main features. Please consult the on-line documentation for details.

  1. The frequency and phase of each DDS can be independently specified.

  2. Each DDS can be put into the power down mode.

  3. The DDS chips can be reset.

  4. The ADC can be read either on demand, or continuously.

  5. The ADC data can be displayed either as volts, or as the hardware data register.

  6. An Overlap Test mode that continuously reads the ADC while modifying the LO DDS phase shift. Conversion performance is measured.

  7. An Options dialog contains a number of settings for customizing gnat.

Starting with version 1.03, gnat supports the LTC2440 ADC chip, the fast detector. This includes support for multiple conversion rates and data averaging. The earlier version of gnat, 1.02, will not function correctly with the 2440 ADC. If you have a 2440, you must upgrade to version 1.03. Version 1.03 also supports the expanded N2PK signal mapping plan, and the OZ multiple speed 2410 ADC (although not yet tested).

System Requirements

gnat has been tested on Windows 98, 2000, and XP. Performance of the CPU is not critical. All other resource requirements are also low. On Windows 2000 and XP, gnat will require the use of a driver that enables the direct access of I/O ports by application programs. One free package that we have tested is UserPort 1.0.

The current gnat self-extracting download file is approximately  400 Kilobytes. The download program is executed to perform the gnat installation. .

gnat help information is viewed through the HTML Help viewer.

Software Download

Through this section you can download the current version of gnat.

When you download gnat, you are actually downloading a self-extracting compressed archive file onto your computer. The downloaded file name is a combination of the program name (gnat) and the program major version number.  In order to install gnat, you must execute the downloaded file. The install program is in the form of the common installation wizard. You will be asked several questions that will customize the installation for your computer.

One of the installed programs is the gnat uninstall program. You should use this program to remove gnat from your computer. The uninstaller will remove all gnat files, and remove gnat-specific entries from the system registry. The uninstall program will also be available from the Add/Remove Programs applet on the Control Panel.

Although gnat includes an uninstall program, you are responsible for the downloaded self-extracting installation wizard file. In other words, the uninstall program does not remove the downloaded file (it removes the installed files). After gnat is installed, the downloaded file may be manually deleted.


Finally, the software. The following table contains the gnat releases, in reverse chronological order (most recent is first).


Release Date

Description (Size)

Download File


History Information


January 23, 2007

Initial release (520 KBytes).


Download Now!


Additional installation and operation information can be found in the on-line documentation (next subsection).

gnat Documentation On-Line

All gnat documentation, both the help information and user's manual, is written in HTML. HTML, the language of the Internet, is also becoming the preferred language for program support documentation. In fact, Windows 98 is shipped with the HTML Help viewer in addition to the older Winhelp viewer.

If you are not running Windows 98, or a more recent compatible operating system, you may not have the HTML Help viewer. The viewer is available from the Microsoft web site, and it will operate on any version of Windows. The viewer will also be automatically installed if you install Internet Explorer 4.0 or higher numbered version.   If you do not have the HTML Help viewer, you will not be able to use the help facilities built into the program, or read the user's manual (through the program). Since the documentation is written in HTML, however, we have placed all of the documentation under this web page. This means that you can access all of the information regardless of your help viewer. You can also read the manual before downloading the software.

Problems, Questions, Comments?

If you have problems, questions, or comments (concerning this software), please contact me via email, at ordy@seed-solutions.com.

License and Legal Notices

gnat  was developed by, and is owned by Seed Solutions, Inc. Copyright , 2004, Seed Solutions, Inc. All rights reserved. No warranty of any kind is made as to performance, or fitness of use in any application. Your use of this software is your agreement with these terms. You agree to hold Seed Solutions, Inc. free from responsibility for any damages that may or may not be associated with the installation or operation of the program.

This software may be redistributed in original form. No fee may be charged for redistribution without the prior and specific written consent of Seed Solutions. Inc. This software is licensed for personal and non-commercial use only, and is subject to the export laws and regulations as defined by the State Department of the United States of America, and other applicable regulatory agencies.

Windows, Windows 95, Windows 98, Windows NT, Windows 2000, Windows ME, Windows XP are either registered trademarks or trademarks of Microsoft Corporation. Other product and company names mentioned on this site may be the trademarks of their respective owners.

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Last update: Tuesday, January 23, 2007 08:49:05 PM
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