22jan16: alfa bm6b instabilities


      Jason hessels (p3055) reported problems with alfa bm 6. he reported problems with data taken:

I finally got around to looking into this using the 20jan16 galfacts data:

Processing the data:

The first set of plots shows the total power vs time for bm0,1, and beam 6 (.ps) (.pdf)

The 2nd set of plots, shows beam 6 vs za and time (.ps) (.pdf)

The za dependence looks like there is something loose.

On 22jan16 we looked at the bias voltages and saw that beam 6a stage 1 biases were jumping around

We monitor the alfa bias's (usually once every 5 minutes). But.. during pulsar experiments, the bias monitoring has to be turned off so it doesn't affect the observations (reading the bias's causes glitches in the bias's output).

The plots below show the measured Drain Current Id for stage 1of the  alfa amplifiers for 01jan-22jan16 (.ps) (.pdf)

I went back and looked at the alfa bias monitoring during jason's runs on 08,17,26 dec15. Unfortunately the bias monitoring was turned off during this time period (the operators turn off the monitoring, but it doesn't always get turned back on when alfa observing is done).


processing:: x101/160121/alfabm6.pro, bm6bias.pro