Interesting project for a network analyzer (aka vector analyzer or VNA, vector network analyzer) is documented here: http://n2pk.com/

It is highly accurate, however the only shortcoming is that it reaches 60MHz only. I intend to build this, and then convert to higher frequencies (using a transverter).

The design is a few years old, but as of 2011, the PCB is available from http://www.makarov.ca/vna_boards.htm and 90% of parts from Digikey UK. The remainder were from Farnell, Coilcraft UK and Minicircuits UK.