Page 1 of 1

Antenna 6 gain calibration varying with time

Posted: Mon Jul 10, 2023 4:59 pm
by and476
I have been taking observations with the 6D configuration. Following calibration, I am finding that for the phase calibrator, the baselines containing antenna 6 have an amplitude and phase that seems to vary with elevation over time. Meanwhile, all the other baselines are flat as expected. See the attached plot. The phase also seems to vary by up to 3-5 deg. This is happening for another phase calibrator I have been working with for a different target source too. Its only about a 2-3% amplitude variation so is this a significant problem?

Re: Antenna 6 gain calibration varying with time

Posted: Wed Jul 12, 2023 8:14 pm
by Mark.Wieringa
I can't see any plot attached. Are you seeing these variations in the uncalibrated data?
Normally variations with elevation should be taken out by the secondary calibration (gpcal on secondary). In any case the variations are quite small and should not affect the target source too much, although it may affect the absolute calibration accuracy of the target flux.
If the target is strong enough to see the effects on the image quality, it is probably also strong enough for self-calibration.