Lband narrow,Lband wide SEFD, Gain, Tsys comparison (daytime)


          The lband narrow (lbn) and lband wide (lbw) systems were compared using position switching on continuum sources.  The correlator with a 25 Mhz bandwidth was used to record the data. Two minute (on time) position switching was followed by a 10 second cal on/off. The routine alternated between lbn and lbw every 4 minutes. The fluxes were taken from the NVSS survey.

  • The sources used were: J0318+164, J0521+164, J0840+132, J1120+143

  • The plots have lbn as a dotted line and lbw as a dashed line. They are:
    1. The SEFD (system equivalent flux density) versus zenith angle.  PolA and polB are plotted separately. The lbn polA values are high (see note (a) below).
    2. The system temperature vs zenith angle (using 1.85, 1.91 Kelvins for the cal values).  polA and polB plotted separately.
    3. The gain versus zenith angle  in kelvins per Jansky using the flux from NVSS and tsys measured using the cal.  PolA and polB plotted separately.
    4. The stability of the cals for each strip (calKelvins/(calon-caloff)). For a given strip the attenuation was not changed so the cal difference should be a constant.
    (a). The lbn receiver's cryogenics was warmed up and then cooled down during the first part of july. After the cycle, the polarization A Tsys increased by 4 degrees kelvin.
    (b).  The lbw OMT provides linear polarization. The tabulated cal values are for this linear mode. After the dewar there is a hybrid that converts linear to circular polarization (this is selectable.. and this data was taken in circular mode). The cal values that were used are the average of  the tabulated polA,polB linear cals. This assumes that the losses from the cal into the hybrid are the same (probably not a great assumption but that's as good as we can do!!).

    The plots can be found at:
    versus za:
      lbn/lbw sefd,gain,tsys vs za (ps)
     lbn/lbw sefd,gain,tsys vs za (pdf)

    versus azimuth:
     lbn/lbw sefd,gain,tsys vs az (ps)
     lbn/lbw sefd,gain,tsys vs az (pdf)

    processing: x101/lb/Aug00/lbnjul00/
    plotting  : x101/lb/Aug00/lbnjul00/12jul00lbnplt{az,za}.pro