Gain and Sefd for multiple receivers using 3C48 and 3C138


      The dish alignment finished in sep01. The calibration data on 3C38 and 3C138 between sep01 and dec01 were used to plot the gain and sefd for various receivers. The flux for these two calibrators is well known. The cal values for some of the receivers (sbw, lbn) is a bit off so these receivers were only included in the SEFD plots (which are independent of the cal).
The figures show:
  • Figure 1 top is the gain versus zenith for: lbw at 1415 MHz, sbn at 2380 MHz, and cband at 5000 Mhz. The lwide data for 3C138 was taken in 13aug01 so the southwest dish adjustment had not yet completed. Any errors in the cal values will carry over to the gain measurements.
  • Figure 1 bottom is the System Equivalent Flux Density (SEFD) in Janskies per Tsys. This plot includes: lbw at 1415 MHz, lbn at 1415Mhz, sbn at 1415Mhz, sbw at 1415 MHz, and cband at 5000 MHz. The best receiver is sbn followed by lbn, sbw, lbw, and then cband.
  • Figure 2 top plots the gain versus frequency for all receivers. Data was taken at za=10Degrees +/- .6 degrees za. Cal errors will also affect this plot.
  • receiver frequencies (Mhz)
    lbw 1175,1300,1375,1415,1550,1610,1666
    sbn 2380
    sbw 2212,2380,2690,2850
    cband 4500,4860,5000,5400
  • Figure 2 bottom is the SEFD versus frequency for za=10+/-.6 degrees for the lbw,sbn,sbw, and cband receivers.
  •     The gain for lband and and sband is relatively flat out to 15 degrees za where it then starts to fall off with za. Sband does have a fall off below 5 degrees za which may be from the pitch and roll error at low za (the wheels  of the dome move over to the carriage house side of the rails). Cband has a za slope in gain probably from the pitch and roll. The opening of 3C48 at cband is caused by the 3 azimuth term of the pitch and roll.

        The SEFD for sbn is 2.5 Jy/Tsys and is relatively flat. Sband wide and lband wide have an increasing slope with za which has been attributed to the over illumination of the tertiary by these two horns.

        The gain versus frequency for lband wide falls off too fast in frequency. The SEFD for these points is relatively flat so the gain falloff is probably an error in the cal versus frequency. The cband gain falloff is also reflected in the sefd increase with frequency so the cals are probably ok.

    processing: x101/calmrcvr/dec01/