Short duration rfi (see by p2558)
Links to plots/tables:
interference (.ps) (.pdf):
Note: after a little thought.. this was probably lightning
p2558 monitors pulsars using the mock spectrometer.
On 31jul11 it took data on J0627+16. When folding the data strong
interference was seen. The setup was:
- 327 MHz rcvr with 57.3 MHz bw centered at 327 MHz. (50 MHz filter
- mock spectrometer used:
- polarization adding
- a/d blanking enabled
- 172.032/3=57.3 MHz bandwidth
- 285.71429 usecs dump time
- Recorded 60 2gb files (each about 67 secsonds long).
The plots show the 327 interference
- Only used the first file to examine the data
- Computed the total power for each dumped spectra (285 usec
- Looked at all spectra whose total power peaks were > 1.2
Tsys in the 1st and 93 records (about 60 seconds apart).
- For the entire file, averaged all spectra whose total power peaks
were > 1.2 Tsys,
- Page 1: total power vs time for the 1st (top) and 93rd (bottom)
- each record (row) holds 2555 285usec spectra (about .7
- The total power is computed over the 57 MHz spectra.
- the total power has been normalized to the median value (making
the units Tsys).
- The red * show all the samples > 1.5 Tsy.
- The green * show the samples 1.2 to 1.5 Tsys
- The rfi is impulsive. It usually lasts for less than 1 sample
(285 usecs). Looking at the entire file, occasionally rfi > 1.2Tsys
can be seen in adjacent samples.
- Page 2:plot spectra with totPwr > 1.5Tsys in records 1
- Top is record 1, bottom in record 93 (spaced by about 60
- The colored spectra are:
- red: the spectra with Tsys > 1.5 Tsys
- black: spectra before the peak
- green: spectra after the peak
- An offset has been added to each set of 3 for display purposes.
- The spectra before and after the peak spectra look normal
- The spectrum of the rfi look relatively stable for the rfi
peaks in 1 record and for records spaced by 60 seconds.
- Page 3: Average all spectra with totpwr > 1.2 Tsys for the 67
- 458 285 usec spectra had totPwr > 1.2 Tsys.
- This is out of 260610 spectra or .18%
- The bandpass was removed from the averaged peak spectrum
- broadband rfi with short time duration (< 285 usecs) is seen
with the 327 rcvr
- For a 67 second sample it occurred .18% of the time.
- The frequency structure of the rfi looks relatively stable over
the 67 second measurement.
- Whatever it is, it is not generating a random frequency
spectrum. So this probably rules out something arcing.