Xband gain curves after new horn and cals.

Oct 2003

Links to the plots:
The oct03 gain curve fits vs az,za

    The xband horn was replaced on 05sep03. On 05oct03 the receiver was removed from turret floor and taken up to the antenna test range to measure the receiver temperature and the cal values.. Calibration data taken 05oct03 through 25jan04 was used to compute the gain curves. The data was taken at 8500, 8800, 9000, and 9200 Mhz. The gain curves were fit as a function of azimuth and zenith angle.  The fitting function (with az,za in degrees) is:

g(az,za)=c0 +c1*(za-10) + c2*(za-10)^2 +c3*(za-10)^3 +
                  c4*cos(az) + c5*sin(az) + c6*cos(2az) + c7*sin(2az) + c8*cos(3az)+c9*sin(3az)
There were 342  measurements at each frequency.

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

Summary of gain fits
freq fit rms

       The data is fit to (polA+polB)/2. The cal values for the two polarization's  give system temperatures that differ by up to 10 Kelvins (45K vs 55K). If you apply the gain curve to a single polarization using its cal value, then the gain may be off . If you compute the gain on both polarization's and then average the values, you will have duplicated what the fitting routines have done. This method will give a better "transfer" of flux from the calibrators used in the fitting to the sources that you are measuring.

     The idl routines gainget() or corhgainget() will now return the xband gain for data after 05oct03 using these fits. The coefficients can be found in the ascii file  data/gain.datR11 (this is provided in the AO idl distribution for correlator routines). You can also find a copy of it at AO in /home/phil/idl/data/gain.datR11.

processing: x101/xb/gain/oct03/dogainfit.pro