I'd like to have an auxiliary receiver dedicated to IQ mixer balancing -- that is, I want to discriminate three tones about 50 MHz apart with 30 dB of dynamic range at a frequency of 6 GHz to 12 GHz. To do this cheaply and simply, I'd like to alias down from NxLO + RF. Does anyone have experience doing this? Are there some inexpensive mixers that are better suited for this than others? It seems like designs that do this don't use mixers that are necessarily specified for it, so is it a matter of testing and figuring out which ones work best?