[Amps] Measuring IMD in a home workshop

[Peter Bertini]

I'm wondering what techniques others are using to make IMD tests for
external RF power amps using test gear that would be commonly found in a
home workshop.

Spectrum Analyzers are cheap enough--I have several vintage HP 141T
analyzers set up, and a very capable Tek 497P with 100/10 Hz RBW.

My problem regarding two or three tone tests is that my rigs all have
comparably terrible IMD.  Several Ten Tec rigs, and a JRC NSD-515.  None of
them have spectacular IMD performance. How do you get around these
limitations?