Does a DC resistance test need to be included with the VNA test to claim full verification of the device? I've attached an older attenuator manual which stipulates calibration frequencies are DC, 4Hz, 12GHz, etc. Newer manuals and OEM calibration certificates have the lowest test point at 50MHz. Was there an agreement made that the DC response can be inferred from the higher frequency test points? Should this lower frequency limitation be identified on the certificate?