Lbw response below 1100 Mhz

Measuring the SEFD around 1100 Mhz
Looking at the rfi

Measuring the SEFD around 1100 Mhz:

    The response of the lbw system was tested on 12feb07 to see if it could be used for galaxies below 1100 Mhz.

The setup:

The standard configuration for lbw has:     To test below 1130 Mhz the setup was:     The wave guide starts to cutoff around 1040 Mhz. A 500 Mhz bandpass centered on 1100 Mhz (via the spectrum analyzer) showed a 6 db difference between 1100 Mhz and the noise floor at 1000 Mhz. The noise floor was being set by the 26 db amp (2 db noise figure)  rather than the sky/omt.

Taking the data:

    On, off position switching using the source B0038+32 (3C19) was used to measure the system performance. It has a flux of 4.09 Jy at 1100 Mhz. The telescope was at za=15.1 degrees when the measurements were made. 2 1 min on/offs were done.  The interim correlator was used with 25 Mhz bands centered at:  1040, 1060, 1080, and 1100 Mhz. The sefd was then computed as:
This becomes Tsys/Gain with units of Janskies.

    The plots show the system performance (.ps) (.pdf) :

 Conclusion: Things to think about:

Looking at the rfi around 1100 Mhz with lbw.

    rfi near 1100 Mhz was monitored with LBW and the interim correlator on 12feb07. A 1200 Mhz low pass filter was used instead of the standard 1120 to 1750 Mhz bandpass filter. 500 1 second dumps were taken with each data set. The frequency channel resolution was 50 Khz (after hanning smoothing). The data sets were:    The plot shows the rms/mean (by frequency channel) (.ps) (.pdf) : Dynamic spectrum for each 25 Mhz band show the time variation of the rfi for the 500 seconds.
The first 4 images are less sensitive than the last 3 since they were taken while tracking a 4 Jy source (doubling Tsys) (you can see this by comparing the two 1080 Mhz bands). The worst rfi is around 1090 Mhz. It gets up to 1.5*Tsys in a 1 second integration and covers 4-5 Mhz.
    processing: x101/070112/