RFI at L-Band (1-2GHz)

Here we present cross correlation spectra on one baseline (antenna 4 and antenna 8) of the EVLA in the D-configuration over the full 1 - 2 GHz L-band bandwidth. This is one of the shortest baselines, and RFI is more pronounced than at other baselines.

The first plot is an overview of the total bandwidth; the next 8 plots each cover 1/8th of the total bandwidth and therefore show much better spectral detail.

Figure 1: An overview of RFI in L-band over the total 1 - 2 GHz band


Figure 2: RFI in L-band from 988 - 1116 MHz. Most RFI seen here originates from aeronautical distance measurement, identification, and radio-location transmissions. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.


Figure 3: RFI in L-band from 1116 - 1244 MHz. Below 1213 MHz we still have aeronautical DME. From 1220 - 1235 MHz we see GPS. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.


Figure 4: RFI in L-band from 1244 - 1372 MHz. Below 1252 MHz the GLONASS navagational satellites produce wide spikes. The narrow RFI features at 1255, 1312, 1330, and 1338 MHz originate from air traffic control radars. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.


Figure 5: RFI in L-band from 1372 - 1500 MHz. The narrow feature at 1408 MHz is internally generated, the twin features at 1463 MHz are due to a resonance in the VLA L-band FE polarizer. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.


Figure 6: RFI in L-band from 1500 - 1628 MHz. INMARSAT from 1525 - 1560 MHz, GPS from 1566 - 1585 MHz, GLONAS from 1600 - 1608 MHz, and Iridium above 1618 MHz. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.


Figure 7: RFI in L-band from 1628 - 1756 MHz. RFI from 1668 and 1690 MHz are from radiosondes (weather balloons) on the low end, and GOES WX satellite transmissions at the high end. The source of the lone spike at 1663 MHz, in the RA band is unknown. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.


Figure 8: RFI in L-band from 1756 - 1884 MHz. Only tiny peaks visible, all of unknown origin. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.


Figure 9: RFI in L-band from 1884 - 2012 MHz. RFI features from 1930 - 1990 MHz are from PCS cell phone base stations. Also available as greyscale plot with time (duration 10 minutes) along the y-axis.