xband cal values measured 06jun03

Ratio of other cals to hcorcal tracking blank sky.
Compare old and new xband cal values.

Links to SECTIONS:
Measuring the high correlated cal using blank sky and absorber
Measuring the other cals on blank sky relative to the high correlated cal.

---

Measuring the high correlated cal using sky and absorber: (top)

    The temperatures used in the computation were:
 

Tabsorber	299. K
Tsky+Tscattered	18 K
Treceiver	from test shack

Each frequency band was measured 6 separate times on the absorber and 6 separate times on the sky. For each measurement the calon/off-1 spectrum was  computed.   A 5th order polynomial was fit to this data to generate the cal values (throwing out any datapoints greater than 2sigma on the first iteration of the fit). The calValue versus frequency plots show the results.

• Fig 1 is the measured cal value in deg K versus frequency. The colors are: Blue is measured using the sky and absorber ratio. Black is using just the absorber and red is using just the sky. The Top plot is polA and the bottom plot is polB. The dashed blue  line is the cal value measured at the antenna test range.. The dash green line is the receiver temperature used (from the antenna test range measurement). The cal value from the sky agrees pretty  well with the values from the absorber and absorber, sky ratio. This means that the Trcvr, Tsky,Trcvr combination is correct.
• Fig 2 is a 5th order polynomial fit to the calAbsorber and calRatio measured values (it will be used to generate the cal value table). The green crosses were used for the fit. The dashed blue line is the cal values measured on the antenna test range.
• Fig 3 and 4 show the cal values for each measurement (polA, polB). The top plot has the 6 measurements on the absorber. The center plot shows the 6 measurements on the sky. The bottom plot is the absorber, sky ratio. There are some jumps in the datataking (eg 8750) These jumps repeat in the sky and absorber measurement (which were separated in time by about 20 minutes) so it is not interference or instabilities in the system.

•  Fig 1. This has the entire 2 Ghz. Top is polA, bottom is polB. Each pass through the frequency range is offset from the previous one for plotting purposes.
• Fig 2-5 has the  same data broken up into 500 Mhz sections.

    The final plot has the power levels during the measurements.

• Fig 1 top is the power at the upstairs fiber optic transmitter for all of the measurements. There were 120*6= 720  records on the sky, and then 720 records on the absorber. The edges of each 120 records (high at low freq:8000 and low at 10Ghz) have a higher spectral density since we are looking at total power and the 1 Ghz IF bandwidth is getting cut off at the edges of the rf band. So the spectral density for the -37 total power was probably ok.
• Fig 1 center is the power at the downstairs if power meter.
• Fig 2 The power counters were not working on the correlator so no data was recorded.
• Fig 3 plots the 25 Mhz 9 level total power measured via the 0 lag of the correlator. A 25 MHz digital filter sits between the power counter of figure 2 and this measurement.

---

Measuring the other cals using sky and the high correlated cal from above.  (top)

• hcorcal(on,off)
• hcal(on,off),hxcal(on,off),h90cal(on,off)
• hcorcal(on,off)
• lcorcal(on,off),lcal(on,off),lxcal(on,off),l90cal(on,off)
• hcorcal(on,off)

    The calOn/calOff -1  spectra was computed for each measurement (giving cal in units of calOff or Tsys).  Each of these 25 Mhz band passes was cumfiltered. This was done on the 3 loops of the same freq band (256 channels *2 numbers). The total power was computed and then the ratio of each cal value relative to the hcorcal was computed (via interpolation of the 3 hcorcal measurements). These values were used to generate the cals table (after multiplying by the hcorcal in kelvins). An 11 order polynomial fit to the data was  done for display purposes (but it was not used to generate the cal values).  The figures show the other cals relative to Tsys and the hcorcal:

• Fig 1. This is the cal value as a fraction of Tsys for each of the cal types. The top figure has the high cals while the bottom figure shows the low cals. The lines with * are polB. The cal types where the same diode feeds the same polarization (polA horcal,hcal.. polB hxcal,hcorcal, etc) are in agreement. Since they were measured at different times, the weather was not having large affect on the data.
• Fig 2. The calType/hcorcal. The top has the high cals while the lower plot is the low cals. The vertical dotted lines show the boundaries for each 100 Mhz measurement. There is a bump in the cal values starting at 9300 Mhz.  The * are an 11th order fit to the data. The higher frequency components of the data are not random (they are correlated between different measurements). Because of this, I used the data rather than the fits to generate the cal values.
• Fig 3. The hcorcal was measured 3 times in each set of 10 measurements. This graph plots the ratio of tsys for the 2ndHcorcal/1stHcorcal (red) and 3rdHcorcal/1stHcorcal (blue). The * have the cal on while the + have the cal off. Each frame is a different pass through the frequency range. These are the raw tsys values. There has been no cumfiltering done yet. If the + and * jump together, then it was Tsys that was changing. If the + and * jump differently then it could have been the cal value. The ratios have interpolated between the 3 hcorcal measurements. Most jumps are within 1%

• The solid lines are the current measurements. The dashed lines were taken with the receiver on the hilltop test range.  The calval values are a bit lower (this decreased Tsys and the gain). The largest  difference is polA below 8500 Mhz.