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To avoid reverse leaking it is necessary to have at minimum 80dB reverse isolation between LO output and mixer input.

This is usually realized? with at minimum 2 20dB amps, a 20dB attenuator at the input, to decouple the LO output, followed by a amp-isolator-amp stage. All very carefully shielded to each other to have a good reverse isolation. Done this for my Tek 492 and Anritsu MS710? SAs. Also as a test setup on the bench for my portable Metronix SA. Because I didn't want to occupy the LO output with my TG I decided to use a directional coupler with -20dB side arm to get a probe of the LO signal. This is a proved concept. My Tek 492 TG was linear within 2dB up to 1.7GHz without leveler. Only by using carefully matched stages and setting the compression points of amps and mixer to the right level. The Metronix SA don't have a LO output and because I didn't want to make the level calibration worse I decided not to put a DC in the LO path, I have build the DC by putting a small wire over a trace with the LO signal to have a linear probe of the LO. It took me a day to get the wire followed by a 20dB decoupling amp formed to be a within 2dB level range at full LO span. So now the Metronix SA has a decoupled LO output.

On all tree SAs the TGs only working in corase span settings, because to get it also working for lower span settings the TG needs to have two mixers, two LO chains with filters and so on, like the original Tek 492 TG was build. But I don't see any need for this much more complex design. The TG is for me a tool to have a source for cable and filter tests on the fly. For sharp filters and so on a NanoVNA is the much better tool. And if you plan to test frequency translation devices like doublers or mixers then a SNA is the simplest and fastest solution, or don't sweep, use a generator and a SA and do step by step scans.

I love this TinySA and also the Ultra. This are very amazing tools with a very high value for the money. For me the next version after the ultra can kill the major brands portable SAs in a second. The advantages of the big player portables are attenuators with wider frequency and power range, maybe mixers with broader range and better harmonic driving capability.

But if I look to the big improvements between the TinySA and the Ultra I can imagine that some thing like a Ultra 2 or Super Ultra could be here in 2 years? with all this improvements build in.

And I have to say this. Erik, your work and your responsiveness are amazing. You set a good example how to make things better for other people. Thank you!

Please continue the improvement.

All the Best,

Isidro