Lbn cal values measured 28jan02

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Phil's computation of the cals:

Each frequency band was measured 9 separate times on the absorber and 21 separate times on the sky. For each measurement the calon/off-1 spectrum was  computed and then the 9 or 21 separate measurements were cumfiltered to remove rfi. The calValue versus frequency plots show the results.

• Fig 1 is the cal value in deg K versus frequency. The * are the measurements and the lines are the cumfiltered values at each 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 purple line is the current cal value (with the 6% error). The light blue line is the current cal value after correcting for the 6% error. The cal value from the sky does not agree very well with the values from the absorber and absorber, sky ratio.
• Fig 2 and 3 show the cal values for each measurement (polA, polB). The top plot has the 9 measurements on the absorber. The center plot shows the 21 measurements on the sky. The bottom plot is the absorber, sky ratio. The center there has jumps in the 1300 to 1400 range. These are source drifting through the beam (4*25Mhz=100 Mhz is measured at each step).

• Fig 1 top is the power at the upstairs fiber optic transmitter for all of the measurements. Each green vertical line delimits a single pass through 1200 to 1600 Mhz (there were 9+21=30 in total). This averages over 500 Mhz and is taken before the start of each 100 Mhz band.
• Fig 1 center is the power at the downstairs if power meter.
• Fig 2 plots the 50 Mhz band (via the power counters) that is input to the correlator 8 bit a/d converter. Top to bottom is correlator board 1 (first 25 MHz of 100 MHz section) through board 4 (last 25 MHz of the 100 Mhz section). The level has been divided by the median value (the scale is linear in power). Up to sample 600 it is relatively clean (we are on the absorber). After this we move to sky and you can see the radar's pop up.
• 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. The rfi does not look as bad. Unfortunately some of the spikes at the 50 MHz stage that are outside the 25 MHz band have probably saturated the a/d converter so the 25 MHz values may be corrupted were there is large rfi in the 50 MHz band.

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Comparing phil's and karen's cal values: (top)

• fig top: The cal values in kelvins. black:karen, red:phil, green: old cal values (after correcting for 6%error).
• fig middle: ratio of "new" cal to old cal. black:karen's computations, red: phil's.
• fig bottom: Ratio of phil's cal values/ karen's cal values.

• Fig 1. Gain versus za. black:lbw gain, green:lbn gain using phil's cals, red: lbn gain using karen's cals. The lbn gain is lower than that of lbw. At 1300 and 1375 Mhz phil's values lie  closer to lbw than karen's. at 1415 both karen's and phil's cal values give the same gain.
• Fig 2. Tsys for lbw and lbn using karen's and phil's cals. A third order polynomial is also fit to the data.
• Fig 3. The SEFD (system equivalent flux density) for lbn and lbw. This is Jy per Tsys and is independent of the cal values.
• Fig 4. If the gains of the lbw and lbn are the same, then the ratio of the LBWsefd/LBNsefd should be determined by the ratio of the system temperatures (which are determined by the cals). This plot compares the SEFD ratio to the Tsys ratio. Black:SEFDLBW/SEFDLBN, red:TsysLbw/TsysLbn using karen's cals. green: TsysLbw/TsysLbn using phil's cal values. The Tsys measurements do not match the sefd ratios. They differ by up to 13 %. For 1300 and 1375 Mhz,Phil's cal values are closer to the sefd ratio than karen's.