Vector Network Analyzers have come down in price to the $100 range, which is amazing in and of itself, so the home experimenter, likely a Ham radio operator, has a lot more capability to precisely measure things that were pure guesswork in the past.

Of course, the anechoic chamber is a nice thing to have. I once got to see the Anechoic chamber at Northrup Grumman near Chicago during a open house... a theater size room they used for various measurements. I'll never forget it.

This is a nice collection of information. The other place to get this type of data in the past was the Amateur Radio Handbook from the ARRL.