On Fri, Mar 1, 2024 at 12:59 PM, Evan Hand wrote:
For best results, keep the input at the TinySA under -25DBm.?
That is approximately -25dBm total power into the tinySA
mixer; and gain/loss before the mixer, whether internal or external, will need to be accounted for.? -25dBm is not a hard and fast number and will vary with instrument and measurement.
One way to check if the level is OK or too high is to add some more attenuation and see if the carrier to intermod/harmonic measurement changes.? If no change then the IM/harmonic is real and not internally-generated.? If it changes, add attenuation until it doesn't.??
The "sweet" spot between distortion and noise can be narrow; some commercial SAs have 1dB (or less) step attenuators for fine level control for this reason.? An external step attenuator can be handy, but watch
its power rating.....
I suspect that the tinySA designer made the internal LNA design such that it will saturate before it damages the mixer; that is what I would do.? What you will get instead is a screen full of massive distortion products, and, I expect, a warning from the instrument; I've never driven mine hard enough to find out.??
73, Don N2VGU
Donald S Brant Jr