Andy G0FTD>> Why not do a port isolation calibration using the 50R load supplied on Ch0, and the supplied SHORT on the input of Ch1 ?
Both ways - to use short or open on CH1 for isolation calibrate are bad. The amplifiers and other circuits have best performance at limited input impedance.
So, it's better to use 50 ¦¸ terminator to reduce noise. Because short or open terminator will leads to higher noise and as result worse calibration.
For ISOLN calibration there is almost no difference if CH0 has load or not. But it has noticeable lower noise with load on CH1.
