The BG7TBL FA-5 frequency counter has become recognized as an excellent choice for experimenters and radio enthusiasts, offering high-spec performance comparable to branded units. But it remains remarkably accessible due to its low cost.
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| FA-5 Frequency counter. |
The FA-5 has powerful hardware. However, most existing control applications lack a good user experience. Many of them rely on scripting languages, such as Python, while others utilise simple command-line interfaces. These limitations inspired us to create FA-5 VizControl. This native application provides a comprehensive, intuitive, and portable desktop experience for managing the FA-5.
We developed FA-5 VizControl using Lazarus and the FPC (Free Pascal Compiler). This choice ensures maximum compatibility and portability. The application functions as a standalone, portable executable on both Linux and Windows operating systems. There is no need for complex installation routines. Users simply download and launch it. Connectivity with the FA-5 uses virtual serial port emulation over USB. Usually, no specialized device drivers are needed.
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| FA-5 VizControl in Linux. |
The GUI provides clear access to all FA-5 control options. Users can select the input source (including the internal 10MHz reference), configure input impedance, and set gate time. Additional toggles are available for essential device parameters, such as input impedance and LPF settings. The GUI also allows users to directly program the default configuration to the FA-5's internal EEPROM via a dedicated menu option.
The lower portion of the FA-5 UI features a real-time data plotting graph, which maps the frequency over sampled points. This immediate graphical feedback is useful for analyzing signal stability or drifts. The user can also view measurements in different scales, ranging from Hz to GHz.
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| FA-5 VizControl in Windows. |
FA-5 VizControl is an open source application. The source code and compiled binaries are available at https://github.com/dilshan/fa5-vizcontrol.



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