p3094: rfi in puppi.. gps
On 20may16 p3094 reported excessive rfi in their
puppi data. Their setup was:
- lband, coherent search, 512 channels over the 800 mhz bw.
- 10 usec dumps.
I Looked at the first file of the scan (after
combining the gpu files)
- 214.5 seconds of data
- 41 gbytes,
- 720 rows, each row .3 seconds
The plots show
the spectra for this file (.pdf):
- Page 1:
- top: overplot the 720 .3 second spectra
- The red dashed lines are the gps satellite frequencies
- plot the GPS L1 power vs time for the file
- i averaged 3.5 Mhz about 1575.2 Mhz
- the oscillations is probably from the scattering of the
satellite signal from some of the beams on the platform
- The signal is getting strong as the scan progresses
- Page 2: gps constellation az,za (relative to AO) for 20may16)
- The transit time of each satellite if printed on the right
- The bottom frame, GPS27 transitted at 12:45:15 (ast).
- it got down to a za of about 8 deg.
- Page 3: angular distance GPS27 and source C0531+33
- This shows the angular distance (degrees) between the
satellite and the source that was being tracked.
- It started off 4.6 degrees from the beam.
- By the end of the first file.. it was 2.5 degrees away
- The rfi reported by the user was probably from the GPS sat svn
- I looked at the first 214 seconds (file 1 of the scan)
- The satellite probably continued to approach the beam in
the files that followed.