Antenna calibration algorithms generally assume that calibration quantities (both in the antennas and in the atmosphere) can be separated on an antenna-by-antenna basis. This provides substantial strength in determining calibration quantities, since (for 27 antennas) 351 baselines of interferometer visibility data may be used to determine 27 individual calibration values, one for each antenna. However, this assumption breaks down for a mixed array of VLA antennas and retrofitted EVLA antennas, since the improved EVLA bandpass response functions are not matched exactly to the poorer (but identical to each other) bandpass responses of VLA antennas. A symptom of the breakdown of this assumption is excessive amplitude closure errors when running the AIPS task CALIB, where the EVLA-EVLA baselines may be reported to have closure errors as high as 3% to 8% for 50 MHz bandpasses, or even larger for narrower bandpasses. The closure errors originate in the mismatch of the VLA-EVLA bandpasses and the CALIB assumption that all calibration quantities are antenna-based, rather than in any EVLA characteristic, but the ultimate result is a miscalibration of the EVLA-EVLA baselines.6For continuum observations, the closure errors may be calibrated by observing a strong calibrator and solving for baseline-dependent errors using the AIPS task BLCAL. For spectral-line observations, the standard bandpass calibrations (e.g., AIPS task BPASS) also will remove the effects of the mismatched bandpasses.