I've designed and built a scalar network analyzer based on the AD9851 and AD8307. I intend to submit an article to the QST magazine, but I need to validate some things. First of all, both components work fabulously. I implemented the 8307 receivers using the recommendations in the data sheet for a low frequency application (fig. 44), but replaced the shunt capacitor on the input with a 6pf cap that enabled higher frequency cutoff. But the data sheet says that this configuration (with 5 kohm resistors on the INP and INM leads) should result in an upper limit of an input voltage of 20V. My unit peaks out at 2.32 v out with a 10V p-p input (50 ohm source). Where am I going wrong?