Peter Jonas (PumpkinEater on the forum) made an antenna analyzer based on a DDS (Direct Digital Synthesizer) module with a built-in AD9851 chip.
This antenna analyzer can be used to find out at which frequencies a short-wave antenna is matched to the 50 Ohm impedance of the cable and the transceiver. This behavior is presented by the so called “voltage standing wave ratio (VSWR)”. To get this value for a frequency range, a Teensy 3.5 controls a DDS (Direct digital synthesizer) signal generator, which sweeps frequencies between 100kHz and 30 MHz. The hf voltages on the signal generator and at the antenna under test are read by the Teensy and compiled by some calculations to derive the VSWR values. The results are shown on a TFT touch display.