2 minute on/offs with a few galaxies
The new jeff mock spectrometer (pdev) was tested on
23jan07. One of the spectrometer boxes was used. The mixers
feeding the spectrometer are a temporary set (the final mixers will have
better rejection, balance, etc..)
The setup was:
An external sample clock was used (locked to the maser).
170 Mhz sampling made each subband 170 Mhz wide.
The sky center frequency was 1375 Mhz. The 2nd los were set -/+ 60 Mhz
from 250 Mhz (so the subbands were centered at (1315,1435 Mhz on the sky).
The spectrometer was configured for 10 millisecond dumps, 8192 channels,
and full stokes using 32 bit outputs.
The synchronization of the spectrometer and the telescope was done manually.
For 1 of the sources the off source did not track the exact path on the
dish as the on src.
Beam 0 of alfa was used to acquire the data.
The 2 minutes of data were averaged and the on/off
-1 was computed. For each galaxy the plots show:
Top plot: (on/off -1) blown up around the frequency of the galaxy. The
vertical scale is in units of Tsys (this is about 3 Jy for alfa). The black
and red traces are polA and polB. They have been offset for plotting purposes
(the dashed black line is there 0 point). The blue line is the average
of polA and pol B. It is 0 based.
center plot: the averaged on source bandpass for the two minutes. Black
is polA, red is polB, green is stokes U, and blue is stokes V (there has
been no corrections to the stokes parameters).
Bottom plot: This is ON/OFF -1 for the entire band. PolA is black while
polB is red (polB is offset for plotting purposes). The vertical scale
is in units of Tsys (about 3 jy). 100 channels (2 Mhz) have been discarded
at the edge of each 170 Mhz band (where the band passes fall off to 0).