Well folks, I just found a second load to put on Ch1 for a test.
Using my calibration method, with nothing on Ch1 at all, just open with a 50R load on Ch0 gives me about -80db noise floor at 250Mhz.
NOTE - That's an averaged figure in my head because there was plus/minus 5db variation on the readout anyway.
Plus/minus 5db, which could also have been advantageous at the right point if anyone was trying some comparison and not using averaging.
Then I did the same but placed a SHORT on Ch1 = no difference,
Did another re-calibration with a load on Ch1. Oh dear big surprise, about 6db WORSE.
Thermal noise in the load being introduced ?
Full reset and full calibration each time, repeated several times.
This was a genuine test, I'm not here to try prove me or anyone else right or wrong here. I just wanted some real evidence for a real education.
Well that's the test, make of it what you want folks ;-)
73 de Andy
