Lband (narrow and wide) SEFD, Gain, Tsys (nightime)
aug 2000 (last modified 09aug00)
The gain, system temperature, and
SEFD as a function of zenith angle were measured using correlator position
switching (with cal on/offs). The position switch was a 1 minute
on, 1 minute move, 1 minute off. The cal was 10 seconds on, off.The measurements
were done at night during july and august. The calibration started with
lbnarrow and then switched to lbwide on 04aug00 because of troubles with
lbnarrow system temperatures. The lbwide measurements were taken as circular
polarization with the hybrid after the dewar inserted.
The measurements were done at 1405, 1460, 1290, and
1370 Mhz with a bandwidth of 6.25 Mhz. The 1400 Mhz fluxes were taken
from the NVSS survey. The fluxes at frequencies 1460, 1290,
and 1370 Mhz were taken from Kuehr et al., A&AS, 45, 367, 1981
and then scaled by Nvss/Kuehr at 1400 Mhz to bring them up to the nvss
epoch. The plots have polA as a dotted line and polB as a dashed
line. They are:
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The SEFD (system equivalent flux density) versus zenith angle.
-
The system temperature vs zenith angle (lbn used 1.85, 1.91 Kelvins for
the cal values. lbw used the tabulated values).
-
The gain versus zenith angle in kelvins per Jansky using the flux
from NVSS/Kuehr and tsys measured using the cal.
-
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.
Connecting the 2 data sets lbn, lbw:
The system temperature for lbn was varying during these
measurements so the sefd is not a reliable measurement. The gain relies
on the flux and the cal values so it should be valid. To put the cal values
for the two receivers on a common (not necessarily correct) scale, two
sources were tracked on both receivers: J1037+331 and J1609+266. A 2nd
order polynomial was fit to gain vs az for the common azimuths and then
the ratio was computed: lbnGain/lbwGain = .95. The daily plots of
data do not have this correction made. The plot of gain vs az,za has gainlbw
scaled by .95 .
Plots of the preliminary analysis by date:
26jul00 J2035+189 (lbn)
02aug00 J1445+099, J1609+266, J1831+291, J0137+331 (lbn)
The first source J1499+099 was done with the correlator levels set too
low.
The dewar was warmed up and then cooled down before this run. The system
temperatures (measured with cals) in polB went from 28 deg K to 35 degrees
K. Since the SEFD also went from 3.7 to 5 (at 10 degrees) it was probably
not the cals that changed. polA remained the same.
The cal scale factor for J0137+331 is changing during the strip. It may
be from sidelobe leakage since this is a 16 Jy source. I need to take a
closer look at the data.
03aug00 J1445+099, J1640+123, J1831+291, J2035+189, J2316+040, B0116+082,
J0318+164 (lbn)
lbn SEFD,
gain, and tsys vs za (ps)
The azimuth stopped with a triangle motion during transit of J2035+189.
On restart, the attenuator values were reset so the calscl has two separate
lines for this source.
04aug00 J1445+099, J1609+266 (lbw)
lbw
SEFD, gain, and tsys vs za (ps)
These two sources were taken in the afternoon between 17:00 and 20:00 hours.
This is where we switched to lbw. You can compare these two sources with
there lbn values taken 02/03aug00.
06aug00 J0006-000, J0129+236, J0431+206 (lbw)
lbw
SEFD, gain, and tsys vs za (ps)
07aug00 J0040+331, J0137+331 (lbw early morning)
lbw
SEFD, gain, and tsys vs za (ps)
07aug00 J1419+064, J1604+012 (lbn evening)
lbn
SEFD, gain, and tsys vs za (ps)
Results:
lb gain vs az,za
(ps)
The gain was computed using the source flux and
cal values for all sources (lbn and lbw) and then plotted versus azimuth
and zenith angle. Each measurement is an arrow with the length proportional
to the gain (1 divison = 5 K/Jy). The angle from the vertical is proportional
to the gain/gainMax (for all measurements). The angle is scaled so that
180 degrees (pointing down) is 50% of the max gain. On the plot, up is
north and to the left is west (azimuth location for source rising). Circles
are drawn every 5 degrees in za, and rays from the center are every 30
degrees. The az,za for each point is at the base of the arrow. The lbw
gain was multiplied by .95 to put it on the same scale as the lbn cals.The
maximum, average, and rms gain (K/Jy) in 5 degree steps was computed
all then data and then for 5 deg za steps.
The system temperature, sefd, and fractional polarization
(actually (gaina-gainb)/(gaina+gainb) since the outputs are circular for
lbn).
gain (K/Jy) for various za ranges
| za range |
max |
avg |
rms |
| all |
9.0 |
7.4 |
.74 |
| 0-5 |
9.0 |
8.6 |
.20 |
| 5-10 |
8.6 |
7.9 |
.37 |
| 10-15 |
8.5 |
7.5 |
.42 |
| 15-20 |
8.4 |
6.8 |
.68 |
lb
gain vs az,za including daytime sources (ps)
Data taken during the day in jun00, jul00 was also included in this
data set. Some of these sources were tracked through midday which may account
for the increased scatter. The rotation angle is scaled to the maximum
gain over the entire dataset and lbw gains are multiplied by .95 to match
the lbn values.
Scripts used to process the data:
26jul00 : processing: x101/lb/Aug00/lbnjul00/26jul00.pro , plotting: x101/lb/Aug00/lbnjul00/26jul00plt.pro
02aug00 : processing: x101/lb/Aug00/lbnaug00/02aug00.pro , plotting: x101/lb/Aug00/lbnaug00/02aug00plt.pro
03aug00 : processing: x101/lb/Aug00/lbnaug00/03aug00.pro , plotting: x101/lb/Aug00/lbnaug00/03aug00plt.pro
04aug00 : processing: x101/lb/Aug00/lbwaug00/04uag00.pro , plotting: x101/lb/Aug00/lbwaug00/04aug00plt.pro
06aug00 : processing: x101/lb/Aug00/lbwaug00/06aug00.pro , plotting: x101/lb/Aug00/lbwaug00/06aug00plt.pro
07aug00 : processing: x101/lb/Aug00/lbwaug00/07aug00.pro , plotting: x101/lb/Aug00/lbwaug00/07aug00plt.pro
07aug00 : processing: x101/lb/Aug00/lbnaug00/07aug00.pro , plotting: x101/lb/Aug00/lbnaug00/07aug00plt.pro
gainAzZa: processing: x101/callb/Aug00/inpall.pro , plotting: x101/callb/Aug00/arrplt.pro, arrplt1.pro
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