PolB instabilities were reported in lband wide
(lbw) in jul10. In sep10
while warming the dewar, the window blew out.
The receiver was brought down to the lab and the window was replaced.
The receiver was reinstalled 25sep10 and cooled down.
Tests were done to check the stability of the
receiver (and also to look at the rfi):
27sep10: 300
second test covering all of lband using the mock spectrometer
29sep10:
4200 second test using the interim correlator and the setup of a2335
(who originally reported the problem).
27sep10: 300
second integration over entire band:
A 300 second test was done with the receiver
on 27sep10. The setup was:
The mock spectrometer was used to cover the entire band.
4 bands of 172 MHz bandwidth and 8192 channels (20KHz resolution)
were used.
The cfr for the bands were: 1200,1350,1500,and 1650 MHz.
3000 .1 second integrations were taken.
The telescope sat at az=285, za=9 degrees.
The data was taken around 17:00 ast. There was some
lightening in the distance.
Processing the data:
dynamic spectra were made for each band (polB)
the average spectra was computed for each band.
the rms/mean by channel was computed for each band.
An rfi mask was generated by finding all rms/mean channels larger
than 3 sigma
The rfi mask was used to compute the total power for each band.
Data plots,images:
PolB images of the 3 bands
each spectra has been normalized to the median spectrum to
flatten the image.
Since the telescope was stationary, continuum sources drift
through the beam.
The vertical scale is seconds (with .1 sec resolution)