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sband wide/low (1.7 to 3.1 Ghz receiver)
sep04
The sband wide (sbw also called sband
low) receiver covers 1.8 to 3.1 ghz. It has a quadridge OMT
(native linear polarization) and a ying/kildal horn. The receiver
was installed on the telescope in 1999 (not sure of these dates). It
never worked very well because of the strong rfi at 1.940 Ghz
(cellular phones) and the 2.4-2.5 ghz pcs band. A filter bank
was built and installed that had filters at 1.7 -1.88,
2.04-2.4, and 2.6-3.1 ghz. With the filter bank installed, the
receiver started to work reliably (out of saturation!!).
History
Recent
system
performance measurements
Daily
monitoring
of Tsys
Dewar
temperatures
Calibration measurements:
Miscellaneous:
cal
values
rfi measurements
History:
- 13jan13: updated pointing offsets.
- 29sep08: installed
new
cal values. backdated to 18aug05.
- 10oct04: installed new cal values. backdated to 15aug04.
- 10sep04: new gain curve installed and back dated to be valid
from 15may04.
- 14may04: cal diodes replaced.
- 14may04: horn moved down in focus direction to put it in
focus.
- 29apr04: horn moved x,y direction after feed survey (focus
motion not yet done).
- 1999-14may2004 The measured
system
temperature drifted from 1999 thru 14may2004. This was
caused by the cal diodes drifting. On 14may04 the diodes were
replaced and the measured system temperature stabilized.
Calibration
measurements:
recent
system
performance
measurements
13jan13:
calibration results: jun12-dec12. updated pointing offset.
26may08: cal values
measured using sky and absorber.
may04-sep04: sbw GAIN CURVES.
may04-sep04: System
performance of data used for gain curves.
09jul04:
cal
values measured using sky and absorber
15aug03:
cal
values measured using sky and absorber
20sep01:
cal
values measured using sky and absorber.
Miscellaneous:
22sep15:retuned notch filters for 2130 rfi
11may15: notched filter to remove aws rfi at 2130
20jan11: rfi appears at 2380
Mhz.
07jun05:
time
for sbw dewar to cool down.
09may03:
resonances
in the sbw receiver.
We sent the sband notched filters back for
retuning. The first set did not fall off fast enough at the
right edge (2155Mhz).
On 22sep15 dana did a 2port network analyzer
measurement on the two filters we got back
The
plots show the 2 port measurements of the filters (.ps) (.pdf)
- Top frame: S21, S11 measurements of the two filters
- s21 (filter transmission):black filter a, red
filter B
- they are down 60db by 2110
- at 2155 they are still down by 55 db
- S11 (filter reflection). Black is filterA, red is filterB
processing: x101/150922/sbwnotchfilter/sbw_filter_2port.pro
11may15: notched filter for aws rfi
We received the notched filter to remove the
AWS rfi around 2130 (more info
on the rfi)
The plots show the results of Dana's 2 port measurement
using the agilent network analyzer (.ps) (.pdf)
- S21 is the loss passsing through the filter
- S11 is the reflected power.
- S22, and S12 were similar
- I also plotted the phase (in deg) for S21
processing:
x101/150525/sbw_filter_2port.pro
May04 to Sep04 fit GAIN
CURVES to calib data. (top...)
link
to
gain curve plot
Gain curves were fit to the sband wide
calibration gain data using 15may04 through 01sep04.
The start of this epoch was after the cals were replaced and the
horn had been lowered put it in focus. The plots show the
gain data (black) and the fits (red) for 2212, 2380, 2690, and
2850 Mhz. These gain equations were installed on 10sep04 and back
data to be valid starting on 15may04.
- Fig 1 shows the az,za distribution for the data. The fit used
a linear fit in za up to za=14. Above 14 degrees terms in
(za-14)^2 and (za-14)^3 were included. The fit also
included 1az, 2az, and 3az sin, cos terms.
- Fig 2 plots the gain data and the fit to za. The fit
equation is printed with the sigma for the fit (in K/Jy).
- Fig 3 plots the fit residuals (data-fit) vs za.
The fit used the za and the azimuth terms. We
probably could have use a little better az,za coverage. I included
the az terms (instead of just a za fit) because it looked like the
1az term had a significant amplitude.
The 2690 freq fit had a lot more scatter than the
other 3 frequencies. If you look at the system performance data for
this data set you'll see that the gain and cals were jumping around
but the sefd was solid. The problem is most likely being caused by
rfi in the cal measurement.
The routine gainget() or corhgainget() will
now return the sbw gain for data after 15may04 from these
equations. The coefficients can be found in the ascii file
data/gain.datR7 (this is provided in the AO idl
distribution for correlator routines). You can also find a copy of
it at AO in /pkg/rsi/local/libao/phil/data/gain.datR7.
Be careful using these routines for data before 15may04. There is
not gain curve and the routine should return and
status reflecting that...
processing: x101/sbw/sep04/dogainfit.pro
may04 to sep04 :
System performance of data used to compute gain curves. (top...)
Heiles calibration scans done from
15may04 (new cals, horn lowered) thru 01sep04 were used to measure
the
system performance. This data was then used to compute the gain
curves for use on data taken after 15may04.
The first set of plots show
the system performance with all frequencies overplotted. The
sources are identified
by symbol and the frequencies by color.
- Fig 1 shows the distributions on the dish of the measurements.
- Fig 2 has the Gain in Kelvins/Jansky. This relies on the cals
and the source flux. The next plot is Tsys vs za in
Kelvins followed by the SEFD (System Equivalent Flux
density) in Janskies / Tsys. At the bottom is the average beam
width in arc seconds.
- Fig 3 plots the coma parameter, first sidelobe height below
the peak, the main beam efficiency, followed by the main beam +
1st sidelobe beam efficiency.
- Fig 4 has the pointing errors in az,za.
The second set of plots has the
data
plotted separately for each frequency. The colors and symbols
are used to differentiate the sources. The figures are:
- Fig 1 2212Mhz Gain,Tsys . 260 points
- Fig 2 2212 Mhz sidelobes,beam efficiencies
- Fig 3 2380 Mhz Gain,Tsys 260 points.
- Fig 4 2380 Mhz sidelobes,beam efficiencies.
- Fig 5 2690 Mhz Gain,Tsys 151 points.
- Fig 6 2690 Mhz sidelobes,beam efficiencies
- Fig 7 2850 Mhz Gain,Tsys 259 points.
- Fig 8 2850 Mhz sidelobes,beam efficiencies
The data for 2690 is jumping around a lot more than the other 3
frequencies. The gain and tsys jump but the sefd is relatively
stable. The cal measurement is probably getting rfi in the cal on or
the cal off causing tsys,gain to jump around.
processing: x101/sbw/sep04/doit.pro
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