Windfreak Technologies published an interesting article called:
(click title below for article at mpddigest.com)
Excerpt:
“USB RF signal generators are actually a hybrid approach to both of those options mentioned above—they can be much cheaper and deliver in a couple of days. A great USA-made example is Windfreak Technologies’ SynthHD Dual Channel Microwave Signal Generator for $1,299. This price is actually cheaper than some RF test cables.”