Using a MiniVNA on the Pocket PC
Vector Network Analysers (VNA's) are very useful tools for measuring signals in terms of their amplitudes and phase changes. However, they are also rather expensive pieces of kit, but cheap alternatives exist for amateur and educational uses. One such cheap, and popular, VNA is the MiniVNA produced by Mini Radio Solutions, which allows measurements on signals up to a frequency of 180MHz. The MiniVNA (not to be confused with the completely different MiniVNA Pro) can be powered by a small battery and connected to a Windows Mobile Pocket PC via BlueTooth. A very simple Pocket PC program is provided which omits most of the really interesting functions included in the PC version of the MiniVNA software. Therefore, as serial communications aren't too complicated in NS Basic CE, VNA Mini was written for the Pocket PC with the intention of trying to provide a similar level of functionality on the Pocket PC as on the PC software.
The software can be downloaded from the links below, and a screen grab of VNA Mini running is shown in Figure 1. The software allows selection of the frequency range, graphing of parameters like amplitude and phase, switching between reflection and transmission measurement modes, and even querying of individual measurement points on the graph (simply tap the graph with your stylus or finger). Simple adjustment to make measurement data relative to a previous measurement is also possible, although this isn't the same as a full VNA calibration due to limitations of the MiniVNA. Also, measurement data can be saved for future use (in CSV format, which can also be loaded into Microsoft Excel), and a bitmap image of the graph can be saved too. Using the export menu the data can even be saved in a format suitable for use with the popular ZPlots spreadsheet analysis tool. Among other useful features is the ability to display a measurement in grey behind new measurements, allowing simple comparison of measurements.
While the MiniVNA and VNA Mini will never rival the accuracy and sophistication of a professional VNA, for many non-critical amateur and educational uses it can be very useful to have a truly inexpensive and portable signal measurement system. Therefore, we hope you enjoy using this free software. For details of how to adapt a Mini VNA to use BlueTooth, please see the MiniVNA manuals on the Mini Radio Solutions website.
Figure 1. VNA Mini in action on a Pocket PC.
All of the files you will need can be found in the sidebar on the left of this page. Please note that this software is written to work in portrait mode on a Pocket PC with a 240x320 pixel colour touch-screen, running Microsoft Windows Mobile OS. NS Basic runtimes can be downloaded at www.nsbasic.com.