sband wide/low (1.7 to 3.1 Ghz receiver)


     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!!).

Recent system performance measurements
Daily monitoring of Tsys
Dewar temperatures
Calibration measurements:
cal values
rfi measurements


Calibration measurements: (top)

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 (top)

170817: Tsys PolB jumps by 10 K on 23mar17.
30may17: testing the correlated cal on sbw.
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.

170817:Tsys polB > Tsys polA, SEFDB/SEFDB (top)

    The Tsys for sbw polB has been higher than Tsys PolA since 23mar17

plot of sbw tsysA,B difference 01jan17 thru 17aug17 (.ps) (.pdf)

    To see if the problem was the cal, or a real problem with the system temperature, i looked at the calibration runs for sbw during 2017. Unfortunately, calibration runs were only done in june and july  of 2017

The gain and Tsys both use the cal value to convert to Kelvins. For the SEFD (Tsys/Gain) the cal dependence cancels out.

The plots show Tsys,gain, and sefd for the jun,july, sbw calibration runs (.ps) (.pdf)


processing: x101/170817/

30may17 testing the correlated cal on sbw (top)

    Joanna rankin reported trouble with the low correlated cal  on sbw. Her data set was:

    The data showed the winking cal was present, but there was no correlation between polA and polB (as if the  2 diode cal was used).

    I checked the cima log files, and the low correlated cal was requested...

On 30may17 i took some data using the mock spectrometer:

Processing the data:

The plots show the results of the test (.ps) (.pdf):


processing: x101/170530/

22sep15: final notched filter for aws rfi (top)

    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)
processing: x101/150922/sbwnotchfilter/

11may15: notched filter for aws rfi (top)

    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)

processing: x101/150525/

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.

    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/

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.

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: 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/