Arduino + AD9850 DDS signal generator
Antenna Analyzer with Arduino Nano and signal generator AD9850 DDS board module - Based on K6BEZ original design
This is a project that can be completed with well under $50 in parts.
The unit doesn't have the precision of the commercial antenna analyzers, however, is very useful to provide with reasonable accuracy an approximation of resonant points of an antenna system.
It helped me a lot to adjust my HF home made antennas. Below are the sweeps of two of them. All the results are confirmed with an external SWR/Watt meter and the SWR built-in the FT-991A.
The unit was calibrated to provide 1:1 SWR reading across all HF bands with a 50 ohms dummy load.