On Sun, Dec 22, 2024 at 02:23 PM, W0LEV wrote:

I learned many decades ago on the job using professional HP
equipment and have never looked back.

HP/Agilent/Keysight still have the best application notes on network analysis and spectrum analysis, both for beginners and for others who want to dig in further. I still have paper copies of many of the old ones.
Merry Christmas, Happy Holidays and a healthy, happy and prosperous New Year to all.
73, Don N2VGU