The network analyser is built around an Arduino Nano driving an AD9850 signal generator. The output is buffered before being fed into the network being analysed. The output of the network is fed into a log amp board and the resulting output fed back into the Nano.
A python script runs on windows 10 that does the setup controlling of the Arduino and this script gives the resulting plots of gain vs frequency.
The Log Amp was purchased on EBay for AU$19.20 and is described as "AD8307 RF Power Detector Board Logarithmic Amplifier DC-500MHz 92db".
The Nano was in the shack bits box with the buffer components. I purchased the AD9850 on EBay for AU$17.30. A small box cost AU$4.00.
See the following diagrams and pictures for a guide of the design and build.