The lband wide receiver was replaced in feb03. The cal values were measured on 6mar03. Data was taken from march through sep03 using the interim correlator. Since the correlator can only measure 4 frequency bands simultaneously, two different frequency groups were used :(1175,1300,1375,1415) and (1415,1550,1610,1666). Gain curves were then computed fitting for gain as a function of za (fits using azimuth terms did not improve the fit enough to make a difference).  The fitting function (with za in degrees) is:

g(za)=c0 +c1*za + c2*(za-14)^2 +c3*(za-14)^3

The plots show the gain fits vs za with the fit residuals.

• Fig 1 shows the az,za distribution for the data. The top plot is the az,za positions for thefrequency group (1175,1300,1375,1415) while the bottom plot has the positions for the (1415,1550,1610,1666) group.
• Fig 2-3 are the individual fits for each frequency. The data is in red, the black lines are the fits. The fit values are listed on each plot. The rms of the fit is listed at: (sigma(y-yfit)) for each plot.
• Fig 4-5 are the fit residuals in K/Jy for each frequency.

      1415Mhz has twice the measurements for the fits since it was included in both frequency groups. The gain increases from 1175 to 1415 Mhz (this could be real or just an error in the cal measurements). Looking at the lbw system performance, you can see that the SEFD is also  increasing as you go to higher frequency. Most of the SEFD increase is from Tsys decreasing but some may be from the cal.

Note: The fits using za and az terms are available for comparison. They are not the curves being used.

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Errors made by using the wrong gain curve

• The top figure plots the two gain curves vs frequency for az=270,za=10. Black is mar03 while red is Nov02.
• The bottom figure is the ratio of the two gain curves vs frequency. This is the error that people have been making by using the incorrect gain curve.  Since the nov02 gain curve was larger, users have been overestimating the telescope gain by up to 8%.

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