Alfa receiver Tsys using the old if/lo system.


    Alfa was installed on 21apr04. We (ganesh , lisa, and myself) measured the alfa system temperature using the alfa high cal. Since the alfa iflo box had not been installed yet, we used the lband wide cables to bring 1 pixel at a time down to the control room using the regular iflo system. Blank sky was tracked during the measurements (ra=11:00:00, dec=23:00:00). The za stayed below 12 degrees za during the measurements. There was no rf filter used and the IF was 750 Mhz and a high side LO.

    The calon/offs were taken (3 seconds on, 3 seconds off). The interim  correlator was setup to take 4*25 Mhz with 1024 channels per band giving a frequency resolution of 48 Khz after hanning smoothing. The band 1220 to 1520 was covered in 3 100 Mhz sets. The entire band (1220 to 1520) was repeated 3 times. The IF bandpass was removed by dividing the cal off spectrum by the cal deflection TsysCalOff/(TsyscalOn-TsyscalOff).
The plots are:

The system temperatures range from 21K (probably a cal error) to 35 K. The cal values were measured in the lab with the noise figure analyzer. This is a first attempt at measuring the alfa cal values. We will redo it using sky and absorber with alfa's LO chassis installed.
processing: x101/040422/calinp,