Cband   polB problems: dec19,jan20


dec19: sefd shows Tsys jump is real, not just a bad calvalue.
dec x111 data shows problem is always there
04jan20: a3123 reports a problem with cband.
10feb20: 2ms sampled spectra show the dropouts are at the crosshead frequency.


    Tsys for cband polB jumped up on 12dec19. It stayed higher than polA until 05jan20 (then we had the earthquakes). When we came back online,  Tsys for polB was still about 3K higher than polA. An oscillation in the system gain was seen on 4jan20.. On 10feb20 it was shown that the dropouts are occurring at the crosshead frequency.

Dec19: SEFD shows tsys jump is real, not a bad cal value.

    The system temperature for polB of the cband (4-6 GHz)  receiver jumped up on 12dec19

The plots show cband Tsys PolA, and PolB as well as TsysPolA-TsysPolB for 2019 (.ps) (.pdf)

SEFD shows real tsys problem.

    A change in Tsys could be a problem with the cals used to measure the Tsys, or a real problem with the system temperature.
The SEFD is the ratio of  Tsys/gain.   Since both of these measurements use the cal values, the ratio cancels out the cal usage. If the SEFD shows a change, it is not because of a problem with the cals values.
    Calibration scans were done with the cband receiver to see if the sefd has changed:

The plots show the SEFD changing similar to the Tsys change (.ps) (.pdf)
processing: x101/191231/

Dec x111 data shows problem is always present

The plots show the total power from the x111 runs during dec19 (.ps) (.pdf)

processing: x101/200210/

04jan20: a3123 reports problem with cband

    A3123 reported a problem with their cband observation on 04jan20.

the plots show the total power  vs time for a 60 seconds of data (.ps) (.pdf)

processing: x101/200210/

200210: 2millisec spectra shows dropouts.

    On 10feb20 data was taken with the mock spectrometer to look into the cband polB problem. the setup was:

The plots show the total power vs time (.ps) (.pdf)

processing: x101/200210/