Lband narrow,Lband wide SEFD, Gain, Tsys comparison (daytime)
12july00
The lband
narrow (lbn) and lband wide (lbw) systems were compared using position
switching on continuum sources. The correlator with a 25 Mhz bandwidth
was used to record the data. Two minute (on time) position switching was
followed by a 10 second cal on/off. The routine alternated between lbn
and lbw every 4 minutes. The fluxes were taken from the NVSS survey.
The sources used were: J0318+164, J0521+164, J0840+132, J1120+143
The plots have lbn as a dotted line and lbw as a dashed line. They
are:
-
The SEFD (system equivalent flux density) versus zenith angle. PolA
and polB are plotted separately. The lbn polA values are high (see note
(a) below).
-
The system temperature vs zenith angle (using 1.85, 1.91 Kelvins for the
cal values). polA and polB plotted separately.
-
The gain versus zenith angle in kelvins per Jansky using the flux
from NVSS and tsys measured using the cal. PolA and polB plotted
separately.
-
The stability of the cals for each strip (calKelvins/(calon-caloff)). For
a given strip the attenuation was not changed so the cal difference should
be a constant.
(a). The lbn receiver's cryogenics was warmed up and then cooled down during
the first part of july. After the cycle, the polarization A Tsys increased
by 4 degrees kelvin.
(b). The lbw OMT provides linear polarization. The tabulated
cal values are for this linear mode. After the dewar there is a hybrid
that converts linear to circular polarization (this is selectable.. and
this data was taken in circular mode). The cal values that were used are
the average of the tabulated polA,polB linear cals. This assumes
that the losses from the cal into the hybrid are the same (probably not
a great assumption but that's as good as we can do!!).
The plots can be found at:
versus za:
lbn/lbw
sefd,gain,tsys vs za (ps)
lbn/lbw
sefd,gain,tsys vs za (pdf)
versus azimuth:
lbn/lbw
sefd,gain,tsys vs az (ps)
lbn/lbw
sefd,gain,tsys vs az (pdf)
processing: x101/lb/Aug00/lbnjul00/12jul00lbnlbw.pro
plotting : x101/lb/Aug00/lbnjul00/12jul00lbnplt{az,za}.pro
home_~phil