A2488: dps with 800 Mhz rcvr
A2488 is using double position switching on sources
using the 800 Mhz receiver. The mock spectrometer is used to record the
data. The setup is:
- 5Mhz, 8Mhz, and 172 Mhz bands taken. Each with 8192 channels.
- 1 second dumps
- 240 seconds on and off source and calibrator.
Compare polA with polB (10aug09)
The observers reported that the rms for polB is
about 70% larger than the rms for polB. This is measured across the dps
The dps processing is:
The processing leaves the dps spectra in units of the bandpass
calibrator source strength.
- Compute onoffSrc=OnSrc-offSrc
- compute onoffBpc = onBpc - offBpc (bpc = bandpass
- dpsSpectra= onoffSrc/onoffBpc
Plots were made of the average spectral
density and rms value for 35 dps spectra (.ps) (.pdf):
- Page 1 vs dps scan number
- top: mean spectra value vs dps scan number. black is pola, red
- Two separate sources/calibrators were looked at.
- there is an oscillation in the dps mean value.
- bottom: Rms value across each spectra vs dps scan number
- Rfi has been removed before computing the rms
- polB rms is greater than polA rms except for the 2nd source.
- Page 2: dps mean spectral value vs az,za
- Top: mean dps spectra value vs azimuth:
- there is a clear 180 deg period implying polarized power
coming in from somewhere.
- bottom: Mean dps spectral value vs za.
- The rms for polB is larger than the rms for polA
- There is polarized power in the average dps spectra. The
amplitude is about 10%. the source is around 1631+11. This is in the
top part of the north polar spur which has polarized power (although
you might expect the calibration to remove this).