Can I use the 16048B with the 4285A for the cable extension?

Yes, the 16048B (Part Number 16048-60030) can be used with the 4285A. But, it is not easy to perform the cable correction using the 100-ohm resistor box (furnished with the 4285A) because the SMC connector leads do not directly match the BNC connectors of the resistor box. Using terminal adapters degrades the accuracy of the cable correction. Instead of the cable correction, it is recommended to perform load compensation at the DUT contact terminals of the test fixture connected to the tip of the 16048B test leads.

Note: Set Cable Length correction function to 1 m to enable the 4285A to be balanced over the entire frequency range.