Receiver Settings

The parameters used for the observation setup are as follows (see table 3.3).

Table 3.3: Observing Setup at the GMRT.

System Parameter	Freq/BW/Time
RF_1 (RR)	614 MHz.
RF_2 (LL)	244 MHz.
LO1_1 (RR)	680 MHz.
LO1_2 (LL)	310 MHz.
LO4_1 (RR)	66 MHz.
LO4_2 (LL)	66 MHz.
IF_1 BW	32 MHz.
IF_2 BW	6 MHz.
BB BW	16 MHz.
CLK_SEL	0
LTA	16.689 sec.

In the table (3.3), in the column 1, RF_1 is the Radio Frequency at the $0^{th}$ channel of the correlator for the RR polarization, RF_2 is the Radio Frequency at the $0^{th}$ channel of the correlator for the LL polarization, LO1_1 is the $I^{st}$ Local Oscillator for RR polarization, LO1_2 is the $I^{st}$ Local Oscillator for LL polarization, LO4_1 is the $IV^{th}$ Local Oscillator for RR polarization, LO4_2 is the $IV^{th}$ Local Oscillator for LL polarization, IF_1 is the Intermediate Frequency bandwidth for RR polarization, IF_2 is the Intermediate Frequency for LL polarization, BB BW is the Baseband Bandwidth used for the observation.

CLK_SEL is the Clock Selection calculated for the sampling frequency used for the observation using the formula $samp\_freq = 32 / 2 ^ {clk\_sel}$ (in this case sampling frequency used is 32 MHz & the channel width was 125 KHz) & LTA is the Long Term Accumulation i.e. integration time for each data point.

The column 2 in the table 3.3 is the value used corresponding to each system parameter given in the column 1.

By shifting the $IV^{th}$ LO from default 70 MHz to 66 MHz, the full IF band of 235 MHz band was shifted to USB. So that the observations were done with the bandwidth of 16 MHz for the 610 MHz band and 6 MHz for the 235 MHZ band with central frequencies being 598 MHz and 236 MHz respectively. USB (Upper Sideband) data was alone used for further analysis.

Using the observational setup described above, we had observations using the Upper Sideband (USB) of the correlator, for one polarization i.e. of 610 MHz of bandwidth 16 MHz, central frequency 606 MHz, 128 channels & channels width 125 KHz and for other polarization i.e. of 235 MHz of bandwidth 6 MHz, central frequency 240 MHz, $\sim$ 48 channels & channel width 125 KHz.