Alfa filter bank switching test

 The setup was:

• Alfa was set to an rf freq of 1375.
• This centered the high freq band at 1450 MHz.
• The low freq band at 1300 MHz was not used for the test.
• The mock spectrometers took a 57 MHz band ,8192 channels, every 1 second.
• Data was taken continously for about 1900 seconds.
• The telescope was stationary during the test.
• While the mock spectrometers were taking data, the alfa filterbank was switched between the wide band filter (300 MHz) and the narrow band filter (100 MHz centered at 1440 MHz).
• A switch occured every 30 seconds.
• at total of 31 complete cycles (narrow then wide filter setting) were taken.
  

Processing the data:

• The narrow and wide band data were separated.
  
• Each of these datasets were normalized to their median value (this made the units Tsys).
• The total power over the 57 MHz was computed
  
• The average spectra was computed for each.

• Each page shows 1 beam.
• The top frame is polA, the bottom frame is polB
• Each frame contains.
• total power vs time for the 31 cycles
• The left 30 seconds is the narrow filter
• the right 30 secs has the wideband filter

• Each page is a separate beam.
• The top Frame is the narrow filter, the bottom frame is the wide filter.
• polA is red, polB is green.
• Ripples are seen in the spectra, but they show up in the all the beams, filters, so they are probably because we were sitting still (no position switching to remove standing waves).
• beam6b (green) is dead so ignore it.

Summary:

• The alfa filter has has trouble switching between narrow band and wide band observing for most of the alfa beams. So something is probably wrong with the switches or drivers.
  
• I don't think that anyone is currently using the narrow band filters (they were used for pulsar search with the wapps before the mocks were ready).
• With the problems switching the filters, it might just be a good idea to bypass the filter bank completely and just have the wide band filter (probably need to do some more checking to make sure that no one is using the narrow filter bank).